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2019, 11 (4) Online: 31 August 2019
• Influence of frost weathering on the recession of surfaces of technogenic landforms in Yakutia
• Andrey E. Melnikov,Nikolay N. Grib
• DOI: 10.3724/SP.J.1226.2019.00257.
• 2019, Vol.11 (4): 257–266 Abstract ( 39) HTML ( 9) PDF (11754 KB) ( 46 )
• The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.

• A paleo-hydrological simulation experiment and its verification in an inland basin
• YuXin Zhang,Yu Li,XinZhong Zhang,ChengQi Zhang,WangTing Ye,Yuan Liu
• DOI: 10.3724/SP.J.1226.2019.00267.
• 2019, Vol.11 (4): 267–282 Abstract ( 21) HTML ( 4) PDF (3347 KB) ( 27 )
• Hydrological circulation, as the most basic material cycle and active natural phenomenon on earth, exerts a significant influence on climate change. The mid-Holocene is an important period to better understand modern environmental change; however, little research has focused on its quantitative simulation of paleo-hydrological process. In this research, we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Basin to reconstruct the mid-Holocene environment and terminal paleo-lake area. Secondly, we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil, air, river and lacustrine sediments in the Shiyang River Basin, and combined the pollen records, as well as quantitatively reconstructed the millennial-scale vegetation zones. Finally, based on the land-cover adjustment results during the mid-Holocene, we successfully used the Soil and Water Assessment Tool (SWAT) model, a modern distributed hydrological watershed model, to simulate mid-Holocene runoff in the basin. Results show that the reconstructed climate in the basin was warmer and moister than that in recent times. Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m, forest at an elevation of 2,550-2,750 m, steppe at an elevation of 1,550-2,150 m and desert steppe below 1,550 m. The upstream, midstream, downstream and average annual runoff of the mid-Holocene in the basin were 16.76×108 m3, 22.86×108 m3, 9.00×108 m3 and 16.20×108 m3 respectively, compared to 15.61×108 m3 of modern annual runoff. Also, the area of terminal paleo-lake in the mid-Holocene was 628 km2. Thus, this study provides a new quantitative method for paleo-hydrological simulation.

• Comparative study of surface energy and land-surface parameters in different climate zones in Northwest China
• JiaXi Yang,ZhenChao Li,Ye Yu,ZhiYuan Zheng,XuHong Hou,XiaoQing Gao
• DOI: 10.3724/SP.J.1226.2019.00283.
• 2019, Vol.11 (4): 283–294 Abstract ( 24) HTML ( 3) PDF (5385 KB) ( 14 )
• Based on observational data of arid, semi-arid and semi-humid areas in Northwest China, the characteristics of surface-water heat transfer and land-surface parameters were compared and analyzed. The results show that the annual mean net radiation was largest in the semi-humid area, followed by the semi-arid area, and then the arid area: 77.72 W/m2, 67.73 W/m2, and 55.47 W/m2, respectively. The annual mean sensible heat flux was largest in the arid area, followed by the semi-arid and semi-humid areas, while latent heat flux showed the reverse. The annual mean sensible heat flux in arid, semi-arid, and semi-humid areas was 85.7 W/m2, 37.59 W/m2, and 27.55 W/m2, respectively. The annual mean latent heat flux was 0 W/m2, 26.08 W/m2, and 51.19 W/m2, respectively. The annual mean soil-heat flux at the 5-cm soil layer in arid, semi-arid, and semi-humid areas was 1.00 W/m2, 0.82 W/m2, and -1.25 W/m2, respectively. The annual mean surface albedo was largest in the arid area, followed by the semi-humid area; and the smallest was in the semi-arid area: 0.24, 0.21, and 0.18, respectively. The annual mean Bowen ratio in the semi-arid area was about 2.06, and that in semi-humid area was about -0.03. The annual mean soil thermal conductivity in the arid, semi-arid, and semi-humid areas was 0.26 W/(m?k), 1.15 W/(m?k), and 1.20 W/(m?k), respectively.

• Holocene lake carbon sequestration, hydrological status and vegetation change, China
• LingMei Xu,Yu Li,WangTing Ye,XinZhong Zhang,YiChan Li,YuXin Zhang
• DOI: 10.3724/SP.J.1226.2019.00295.
• 2019, Vol.11 (4): 295–326 Abstract ( 15) HTML ( 2) PDF (12602 KB) ( 19 )
• Lakes have received considerable attention as long-term sinks for organic carbon (C) at regional and global scales. Previous studies have focused on assessment and quantification of carbon sinks, and few have worked on the relationship between millennial-scale lake C sequestration, hydrological status and vegetation, which has important scientific significance in improving our understanding of lake C stocks and storage mechanisms. Here, we present a comprehensive study of pollen records, organic geochemical proxies, lake-level records, sediment accumulation rate (SAR) and organic C accumulation rate (CAR) in China since the Holocene. We also include numerical climate classification and lake-level simulations, to investigate variations of lake C sequestration, hydrological status and vegetation during the Holocene. Results indicate that the evolution of lake C accumulation showed an out-of-phase relationship with hydrological status and vegetation in China. Lake C accumulation exhibited an overall trend of increasing from the early to late Holocene in response to gradually increasing terrestrial organic matter input. However, China as a whole experienced the densest vegetation cover in the middle Holocene, corresponding to the mid-Holocene optimum of a milder and wetter climate. Optimal hydrological conditions were asynchronous in China; for example, early Holocene in Asian monsoon dominated areas, and middle Holocene in westerlies controlled regions. Our synthesis indicated that climate change was the main factor controlling the long-term variability in lake C accumulation, hydrologic conditions, as well as vegetation, and human influences were usually superimposed on the natural trends.

• Effects of gibberellic acid on tiller-bulb number and growth performance of Lilium davidii var. unicolor
• YuHui He,ZhongKui Xie,XinPing Liu,YaJun Wang,YuBao Zhang,Yang Qiu
• DOI: 10.3724/SP.J.1226.2019.00327.
• 2019, Vol.11 (4): 327–334 Abstract ( 16) HTML ( 2)
• Lilium davidii var. unicolor (Lanzhou lily) is an important economic crop in the northwest cold and arid regions of China. Effective regulation of tiller-bulb development and plant growth is the key to improving yield and quality of the lily. This study attempted to evaluate the effect of gibberellic acid (GA3) on tiller-bulb development and plant growth of Lanzhou lily by applying GA3 at various concentrations (0 mg/L, 10 mg/L, 30 mg/L, 60 mg/L, and 100 mg/L) before planting and in the seedling period. Results showed that the 60-mg/L GA3 application had an inhibiting effect on tiller-bulb formation and increased the ratios of single and double bulbs but decreased the ratios of bulbs with three or more tiller bulbs, as compared to the control (CK) and other GA3 treatments. The difference in flower number did not reach significant levels among the treatments. The tillering-related endogenous hormones IAA (indole-3-acetic acid) and Z (zeatin) content decreased, while IAA/Z increased with the 60-mg/L GA3 treatment during tiller initiation. And also, the shoot-bulb number and total daughter-bulb number decreased significantly with the 60-mg/L GA3 treatment. Furthermore, the 10-mg/L GA3 application promoted growth of Lanzhou lily significantly and resulted in an increase in plant height; bulb diameter; bulb circumference; and biomass of shoots, bulbs, fibrous roots, and the whole plant. Therefore, GA3 application is promising as a new regulation method for inhibiting tiller-bulb development and promoting bulb growth in Lanzhou lily production.

2019, Vol.11 No.3 No.2 No.1
2018, Vol.10 No.6 No.5 No.4 No.3 No.2 No.1
2017, Vol.9 No.6 No.5 No.4 No.3 No.2 No.1
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2015, Vol.7 No.6 No.5 No.4 No.3 No.2
• Study of thermal properties of supraglacial debris and degree-day factors on Lirung Glacier, Nepal
• Mohan Bahadur Chand,Rijan Bhakta Kayastha
• DOI:10.3724/SP.J.1226.2018.00357
• 2018, 10 (5): 357–368 Abstract (187) HTML (23) PDF (4797 KB) (115)
• The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.

• Analysis of vegetation changes and dominant factors on the Qinghai-Tibet Plateau, China
• HongWei Wang,Yuan Qi,ChunLin Huang,XiaoYing Li,XiaoHong Deng,JinLong Zhang
• DOI:10.3724/SP.J.1226.2019.00150.
• 2019, 11 (2): 150–158 Abstract (44) HTML (5) PDF (34922 KB) (66)
• This research was undertaken to clarify the characteristics of vegetation change and its main influencing factors on the Qinghai-Tibet Plateau. Using the greenness rate of change (GRC) and correlation factors, we analyzed the trend of vegetation change and its dominant factors from 2000 to 2015. The results indicate that the vegetation tended to improve from 2000 to 2015 on the Qinghai-Tibet Plateau, with the improved area accounting for 39.93% of the total; and the degraded area accounting for 19.32%. The areas of degraded vegetation are mainly concentrated in the low-relief and intermediate-relief mountains of the high-altitude and extremely high-altitude areas on the Qinghai-Tibet Plateau, as the vegetation characteristics are impacted by the terrain. Temperature and precipitation have obvious response mechanisms to vegetation growth, but the effects of precipitation and temperature on vegetation degradation are not significant over a short time frame. Overgrazing and population growth are the dominant factors of vegetation degradation on the Qinghai-Tibet Plateau.

• Stable isotopes reveal varying water sources of Caragana microphylla in a desert-oasis ecotone near the Badain Jaran Desert
• Hai Zhou,WenZhi Zhao,ZhiBin He,Heng Ren
• DOI:10.3724/SP.J.1226.2018.00458
• 2018, 10 (6): 458–467 Abstract (51) HTML (7) PDF (10064 KB) (54)
• Understanding the variation in a plant's water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios (δ18O) of xylem water of Caragana microphylla, precipitation, soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub. We found that the water sources of C. microphylla differed with the plant's ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer, the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.

• Review on simulation of land-surface processes on the Tibetan Plateau
• Rui Chen,MeiXue Yang,XueJia Wang,GuoNing Wan
• DOI:10.3724/SP.J.1226.2019.00093.
• 2019, 11 (2): 93–115 Abstract (48) HTML (9) PDF (9572 KB) (51)
• The Tibetan Plateau (TP) has powerful dynamics and thermal effects, which makes the interaction between its land and atmosphere significantly affect climate and environment in the regional or global area. By retrospecting the latest research progress in the simulation of land-surface processes (LSPs) over the past 20 years, this study discusses both the simulation ability of land-surface models (LSMs) and the modification of parameterization schemes from two perspectives, the models' applicability and improved parameterization schemes. Our review suggests that different LSMs can well capture the spatiotemporal variations of the physical quantities of LSPs; but none of them can be fully applied to the plateau, meaning that all need to be revised according to the characteristics specific to the TP. Avoiding the unstable iterative computation and determining the freeze?thaw critical temperature according to the thermodynamic equilibrium equation, the unreasonable freeze?thaw parameterization scheme can be improved. Due to the complex underlying surface of the TP, no parameterization scheme of roughness length can well simulate the various characteristics of the turbulent flux over the TP at different temporal scales. The uniform soil thermodynamic and hydraulic parameterization scheme is unreasonable when it is applied to the plateau, as a result of the strong soil heterogeneity. There is little research on the snow-cover process so far, and the improved scheme has no advantage over the original one due to the lack of some related physical processes. The constant interaction among subprocesses of LSPs makes the improvement of a multiparameterization scheme yield better simulation results. According to the review of existing research, adding high-quality observation stations, developing a parameterization scheme suitable for the special LSPs of the TP, and adjusting the model structures can be helpful to the simulation of LSPs on the TP.

• Characterization of landscape pattern based on land economic niche change: A case study in Ganzhou, Gansu Province, China
• HuaLi Tong, PeiJi Shi, XueBin Zhang, ZaiYan Li
• DOI:10.3724/SP.J.1226.2018.00261
• 2018, 10 (3): 261–270 Abstract (16) PDF (1614 KB) (48)
• Land use change has a profound impact on biodiversity and ecological processes, and is closely related to changes in landscape patterns. This paper introduces the theory and method of land economic niche into landscape ecology, which provides a new method for spatial characterization of urban and rural spatial landscape patterns. Based on this theory, this paper analyzes the landscape pattern of Ganzhou District by using Landsat images as data source in 1995, 2000, 2005, 2010 and 2015. We calculated the land economic niche by applying the niche potential theory. Combined with the theory of landscape ecology, we explored the effects of the land economic niche change on the landscape pattern at a county scale. The results show that economic niche of construction land, watershed and farmland increased during 1995-2015, and grassland declined significantly. The economic niche of farmland, construction land, watershed and grassland show a negative correlation with the number of patches (NP), fragmentation index (FN) and the fractal dimension index (FD), and had a positive correlation with the aggregation index (AI). There was no significant correlation between the forest land economic niche and landscape metrics. The change of land economic niche has a driving effect on the landscape pattern of the county, which can represent the economic development direction of Ganzhou District. The land economic niche is closely related to the landscape type which can directly obtain an economic benefit.
• Influence of frost weathering on the recession of surfaces of technogenic landforms in Yakutia
• Andrey E. Melnikov,Nikolay N. Grib
• DOI:10.3724/SP.J.1226.2019.00257.
• 2019, 11 (4): 257–266 Abstract (39) HTML (9) PDF (11754 KB) (46)
• The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.

• Spatial variations of Pb, As, and Cu in surface snow along the transect from the Zhongshan Station to Dome A, East Antarctica
• XingXing Jiang, ShuGui Hou, YuanSheng Li, HongXi Pang, Rong Hua, Mayewski Paul, Sneed Sharon, ChunLei An, Handley Michael, Ke Liu, WangBin Zhang
• DOI:10.3724/SP.J.1226.2018.00219
• 2018, 10 (3): 219–231 Abstract (23) PDF (1847 KB) (41)
• The spatial distributions of lead, arsenic, and copper (Pb, As, and Cu, respectively) in surface snow along the transect from the Zhongshan Station to Dome A, East Antarctica, are presented. The mean concentrations of Pb, As, and Cu are 1.04±1.56 pg/g, 0.39±0.08 pg/g, and 11.2±14.4 pg/g, respectively. It is estimated that anthropogenic contributions are dominant for Pb, As, and Cu. Spatially, Pb concentrations show an exponentially decreasing trend from the coast inland, while a moderate decreasing trend is observed for Cu concentrations in the coastal area (below 2,000 m above sea level (a.s.l.)). In the intermediate area (2,000-3,000 m a.s.l.), the concentrations and enrichment factors of all these elements show high variability due to the complicated characteristics of climate and environment. On the inland plateau (above 3,000 m a.s.l.), the high concentrations of As and Pb are induced by high deposition efficiency, the existence of polar stratospheric precipitation, and the different fraction deposition to East Antarctica. The extremely high concentrations with maximum values of 9.59 pg/g and 69.9 pg/g for Pb and Cu, respectively, are suggested to result mainly from local human activities at the station. Our results suggest that source, transport pathway, and deposition pattern, rather than distance from the coast or altitude, lead to the spatial distributions of Pb, As, and Cu; and it is further confirmed by spatial variations of the three metals deposited over the whole continent of Antarctica.
• Effects of N:P ratio of Artemisia ordosica on growth influenced by soil calcium carbonate
• YuTing Liang,XingDong He,JianTan Guo,HongJuan Jing
• DOI:10.3724/SP.J.1226.2018.00333
• 2018, 10 (4): 333–339 Abstract (28) HTML (2) PDF (1442 KB) (39)
• Soil calcium carbonate (CaCO3) has a strong solid phosphorus effect, and high content of CaCO3 can significantly reduce the effectiveness of soil phosphorus. To reveal the limiting effect of soil CaCO3 on the growth of plants on sand land and its mechanism of plant physiology, we performed pot experiments with a two-factor randomized block design and a three-factor orthogonal design for different soil CaCO3 content treatments using Artemisia ordosica seedlings. In the experiments, we surveyed plant height, aboveground biomass, root length and root weight and analyzed N, P concentrations and RNA content of the seedlings, and discussed the relationships between relative growth rate (RGR) of the seedlings and N:P ratio as well as RNA. Results show that, the RGRs of plant height and above-ground biomass of the seedlings decreased significantly with the increase of soil CaCO3 content, and those for root length and root weight decreased. The RGRs of plant height and above-ground biomass of the seedlings were significantly negatively correlated with leaf N:P ratios, but significantly positively correlated with leaf RNA content and leaf P concentrations. It can be seen that soil CaCO3 is a stress factor for the growth of A. ordosica seedlings, and the growth response of the seedlings under the influence of soil CaCO3 is in line with the Growth Rate Hypothesis.

• Intersection-pavement de-icing: comprehensive review and the state of the practice
• Yang ZhaoHui Joey
• DOI:10.3724/SP.J.1226.2019.00001
• 2019, 11 (1): 1–12 Abstract (63) HTML (12) PDF (925 KB) (35)
• Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application.

• Studies on eco-environmental change in source regions of the Yangtze and Yellow Rivers of China:present and future
• JianPing Yang
• DOI:10.3724/SP.J.1226.2019.00173.
• 2019, 11 (3): 173–183 Abstract (60) HTML (6) PDF (2405 KB) (34)
• The source regions of the Yangtze and Yellow Rivers are important in the field of eco-environmental change research in China because of its distinct alpine ecosystem and cryosphere environment. At present, there are three different concepts on the extent of source areas of the Yangtze and Yellow Rivers: hydrological, geographical, and eco-environmental. Over the past decades, annual average air temperature has warmed significantly; moreover, the temperature rise rate increases notably with increase of time of the data series. Annual precipitation has no obvious increase or decrease trend, and the climate has become warm and dry in the source regions. As a result, the cryosphere in the regions has shrunk significantly since 1960s. A warm and dry climate and changing cryosphere together induced a substantial declination of alpine wetlands, marked decrease in river runoff, significant degradation of alpine grassland, and a reduction of engineering stability. The ecological environment, however, has a tendency for restoration in the regions because the climate has become gradually warm and wet since 2000. Thus, studies on eco-environmental change is transforming from a single element to multidisciplinary integration. Climate change-cryopshere change-physical and socioeconomic impacts/risk-adaptation constitute a chain of multidisciplinary integration research.

• Numerical simulation of the climate effect of high-altitude lakes on the Tibetan Plateau
• YinHuan Ao,ShiHua Lyu,ZhaoGuo Li,LiJuan Wen,Lin Zhao
• DOI:10.3724/SP.J.1226.2018.00379
• 2018, 10 (5): 379–391 Abstract (44) HTML (5) PDF (5751 KB) (32)
• Lakes regulate the water and heat exchange between the ground and the atmosphere on different temporal and spatial scales. However, studies of the lake effect in the high-altitude Tibetan Plateau (TP) rarely have been performed until recently, and little attention has been paid to modelling of frozen lakes. In this study, the Weather Research and Forecasting Model (WRF v. 3.6.1) is employed to conduct three numerical experiments in the Ngoring Lake Basin (the original experiment, an experiment with a tuned model, and a no-lake experiment) to investigate the influences of parameter optimization on the lake simulation and of the high-altitude lake on the regional climate. After the lake depth, the roughness lengths, and initial surface temperature are corrected in the model, the simulation of the air temperature is distinctly improved. In the experiment using a tuned model, the simulated sensible-heat flux (H) is clearly improved, especially during periods of ice melting (from late spring to early summer) and freezing (late fall). The improvement of latent-heat flux (LE) is mainly manifested by the sharp increase in the correlation coefficient between simulation and observation, whereas the improvement in the average value is small. The optimization of initial surface temperature shows the most prominent effect in the first year and distinctly weakens after a freezing period. After the lakes become grassland in the model, the daytime temperature clearly increases during the freezing and melting periods; but the nocturnal cooling appears in other stages, especially from September to October. The annual mean H increases by 6.4 times in the regions of the Ngoring Lake and the Gyaring Lake, and the LE declines by 56.2%. The sum of H and LE increases from 71.2 W/m2 (with lake) to 84.6 W/m2 (no lake). For the entire simulation region, the sum of H and LE also increases slightly. After the lakes are removed, the air temperature increases significantly from June to September over the area corresponding to the two lakes, and an abnormal convergence field appears; at the same time, the precipitation clearly increases over the two lakes and surrounding areas.

• The establishment and development of Haloxylon ammodendron promotes salt accumulation in surface soil of arid sandy land
• YongZhong Su,TingNa Liu,JunQia Kong
• DOI:10.3724/SP.J.1226.2019.00116.
• 2019, 11 (2): 116–125 Abstract (35) HTML (3) PDF (1590 KB) (32)
• Haloxylon ammodendron, a representative C4 succulent xerophyte and salt-secreting plant, is widely used in vegetation reestablishment programs to stabilize shifting sand, and is one of the dominant shrubs in the shelter belt used to control desertification in the desert-oasis ecotone in northwestern China. In this study, we collected soil samples in an age sequence of 0-, 2-, 5-, 13-, 16-, 31-, and 39-year-old H. ammodendron plantations to assess the effects of the shrub on soil fertility and salinity. Results show that SOC and total N concentrations increased significantly with increasing plantation age and increased 5.95- (in the interspaces) to 9.05-fold (under the canopy) and 6.15- to 8.46-fold at the 0?5 cm depth at the 39-year-old plantation compared with non-vegetated sandy land. Simultaneously, H. ammodendron establishment and development resulted in significant salt accumulation in the surface layer. On average, total soil salt content at the 0?5 cm and 5?20 cm depth increased 16.8-fold and 4.4-fold, respectively, compared with non-vegetated sandy land. The increase of total salt derived mostly from the accumulation of SO $4 2 -$ , Ca2+ and Na+ with H. ammodendron development. The accumulation in salinity was more significant than the increase in fertility, suggesting that improved soil fertility did not limit the impact of salinization. The adverse effect of salt accumulation may result in H. ammodendron plantation degradation and impact community stability in the long run.

• Comparison of temperature extremes between Zhongshan Station and Great Wall Station in Antarctica
• AiHong Xie,ShiMeng Wang,YiCheng Wang,ChuanJin Li
• DOI:10.3724/SP.J.1226.2018.00369
• 2018, 10 (5): 369–378 Abstract (62) HTML (15) PDF (4839 KB) (29)
• Although temperature extremes have led to more and more disasters, there are as yet few studies on the extremes and many disagreements on temperature changes in Antarctica. Based on daily minimum, maximum, and mean air temperatures (Tmin, Tmax, Tmean) at Great Wall Station (GW) and Zhongshan Station (ZS), we compared the temperature extremes and revealed a strong warming trend in Tmin, a slight warming trend in Tmean, cooling in Tmax, a decreasing trend in the daily temperature range, and the typical characteristic of coreless winter temperature. There are different seasonal variabilities, with the least in summer. The continentality index and seasonality show that the marine air mass has more effect on GW than ZS. Following the terminology of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), we defined nine indices of temperature extremes, based on the Antarctic geographical environment. Extreme-warm days have decreased, while extreme-warm nights have shown a nonsignificant trend. The number of melting days has increased at GW, while little change at ZS. More importantly, we have found inverse variations in temperature patterns between the two stations, which need further investigation into the dynamics of climate change in Antarctica.

• Applying the AHP-FUZZY method to evaluate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau: a case study of Chaidaer-Muli Railway
• Wei Cao,Yu Sheng,Ji Chen,JiChun Wu
• DOI:10.3724/SP.J.1226.2018.00447
• 2018, 10 (6): 447–457 Abstract (54) HTML (10) PDF (480 KB) (29)
• This article attempts to investigate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau. As a case study, Chaidaer-Muli Railway is used to evaluate the measure effect of rubble roadbed engineering in permafrost regions. The AHP (Analytic Hierarchy Process) method is thus employed to establish the evaluation indicator system. The evaluation factor is selected by analyzing the mutual relation between the permafrost environment and roadbed engineering. Thus, a hierarchical structure model is established based on the selected evaluation indices. Each factor is weighted to determine the status in the evaluation system, and grading standards are built for providing a basis for the evaluation. Then, the fuzzy mathematical method is introduced to evaluate the measure effect of rubble roadbed engineering in permafrost regions along the Chadaer-Muli Railway. Results show that most of the permafrost roadbed is in a preferable condition (b) along the Chaidaer-Muli Railway due to rubble engineering measures. This proportion reaches to 86.1%. The proportion in good (a), general (c) and poor states (d) are 0.0%, 7.5% and 6.4%, respectively, in all the evaluation sections along the Chaidaer-Muli Railway. Ground-temperature monitoring results are generally consistent with AHP-FUZZY evaluation results. This means that the AHP-FUZZY method can be applied to evaluate the effect of rubble roadbed engineering measures in permafrost regions. The effect evaluation of engineering measures will provide timely and effective feedback information for further engineering design. The series of engineering measures will more effectively protect permafrost stability.

• The changing process and trend of ground temperature around tower foundations of Qinghai-Tibet Power Transmission line
• YanLi Xie, QiHao Yu, YanHui You, ZhongQiu Zhang, TingTao Gou
• DOI:10.3724/SP.J.1226.2019.00013
• 2019, 11 (1): 13–0020 Abstract (36) HTML (9) PDF (10529 KB) (29)
• After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission (QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons, while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.

• Shifts in community structure and function of ammonia-oxidizing archaea in biological soil crusts along a revegetation chronosequence in the Tengger Desert
• LiNa Zhao,XinRong Li,ShiWei Yuan,YuBing Liu
• DOI:10.3724/SP.J.1226.2019.00139.
• 2019, 11 (2): 139–149 Abstract (44) HTML (1) PDF (2660 KB) (29)
• Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea (AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts (BSCs) of desert ecosystems remain poorly understood. Here, we utilized Illumina MiSeq sequencing and microbial functional gene array (GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria (AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.

• Assessing the impacts of ecological-living-productive land changes on eco-environmental quality in Xining City on Qinghai-Tibet Plateau, China
• ZiYi Gao,HaiFeng Zhang,XiaoNan Yang,ZhiYuan Song
• DOI:10.3724/SP.J.1226.2019.00194.
• 2019, 11 (3): 194–207 Abstract (37) HTML (2) PDF (5003 KB) (29)
• The Ecological-living-productive land (ELPL) classification system was proposed in an effort to steer China’s land pattern to an ecological-centered path, with the development model shifting from a single function into more integrated multi-function land use. The focus is coordinating the man-land contradictions and developing an intensive, efficient and sustainable land use policy in an increasingly tense relationship between humans and nature. Driven by socioeconomic change and rapid population growth, many cities are undergoing urban sprawl, which involves the consumption of cropland and ecological land and threatens the ecological balance. This paper aims to quantitatively analyze the critical effects of ELPL changes on eco-environmental quality according to land use classification based on leading function of ecology, living and production from 1990 to 2015 with a case study of Xining City. Also, four future land use scenarios were simulated for 2030 using the Future Land Use Simulation (FLUS) model that couples human and natural effects. Our results show a decrease in productive land (PL) and an increase in ecological land (EL) and living land (LL) in Xining City. Forestry ecological land (FEL) covered the top largest proportion; agriculture productive land (APL) showed the greatest reduction and urban and rural living land (U-RLL) presented a dramatic increase. The eco-environmental quality improved in 1990-2010, mainly affected by the conversion of APL to FEL and GEL. However, the encroachment of U-RLL into APL, other ecological land (OEL) and FEL was the main contributor to the decline in eco-environmental quality in 2010-2015 as well as the primary reason for the increase area of lower-quality. The Harmonious Development (HD)-Scenario, characterized by a rational allocation of LL and PL and a better eco-environment, would have implications for planning and monitoring future management of ELPL, and may represent a valuable reference for local policy-makers.

• Altitude pattern of carbon stocks in desert grasslands of an arid land region
• Rong Yang,JunQia Kong,ZeYu Du,YongZhong Su
• DOI:10.3724/SP.J.1226.2018.00404
• 2018, 10 (5): 404–412 Abstract (28) HTML (3) PDF (4973 KB) (28)
• For estimating the altitude-distribution pattern of carbon stocks in desert grasslands and analyzing the possible mechanism for this distribution, a detailed study was performed through a series of field vegetation surveys and soil samplings from 90 vegetation plots and 45 soil profiles at 9 sites of the Hexi Corridor region, Northwestern China. Aboveground, belowground, and litter-fall biomass-carbon stocks ranged from 43 to 109, 23 to 64, and 5 to 20 g/m2, with mean values of 80.82, 44.91, and 12.15 g/m2, respectively. Soil-carbon stocks varied between 2.88 and 3.98 kg/m2, with a mean value of 3.43 kg/m2 in the 0–100-cm soil layer. Both biomass- and soil-carbon stocks had an increasing tendency corresponding to the altitudinal gradient. A significantly negative correlation was found between soil-carbon stock and mean annual temperature, with further better correlations between soil- and biomass-carbon stocks, and mean annual precipitation. Furthermore, soil carbon was found to be positively correlated with soil-silt and -clay content, and negatively correlated with soil bulk density and the volume percent of gravel. It can be concluded that variations in soil texture and climate condition were the key factors influencing the altitudinal pattern of carbon stocks in this desert-grassland ecosystem. Thus, by using the linear-regression functions between altitude and carbon stocks, approximately 4.18 Tg carbon were predicted from the 1,260 km2 of desert grasslands in the study area.

• Vulnerability and adaptation of an oasis social–ecological system affected by glacier change in an arid region of northwestern China
• JianPing Yang, Man Li, ChunPing Tan, HongJu Chen, Qin Ji
• DOI:10.3724/SP.J.1226.2019.00029
• 2019, 11 (1): 29–0040 Abstract (50) HTML (3) PDF (11448 KB) (27)
• The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis social-ecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis (SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-, medium-, and long-term adaptation initiatives are put forward in the article.

• A paleo-hydrological simulation experiment and its verification in an inland basin
• YuXin Zhang,Yu Li,XinZhong Zhang,ChengQi Zhang,WangTing Ye,Yuan Liu
• DOI:10.3724/SP.J.1226.2019.00267.
• 2019, 11 (4): 267–282 Abstract (21) HTML (4) PDF (3347 KB) (27)
• Hydrological circulation, as the most basic material cycle and active natural phenomenon on earth, exerts a significant influence on climate change. The mid-Holocene is an important period to better understand modern environmental change; however, little research has focused on its quantitative simulation of paleo-hydrological process. In this research, we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Basin to reconstruct the mid-Holocene environment and terminal paleo-lake area. Secondly, we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil, air, river and lacustrine sediments in the Shiyang River Basin, and combined the pollen records, as well as quantitatively reconstructed the millennial-scale vegetation zones. Finally, based on the land-cover adjustment results during the mid-Holocene, we successfully used the Soil and Water Assessment Tool (SWAT) model, a modern distributed hydrological watershed model, to simulate mid-Holocene runoff in the basin. Results show that the reconstructed climate in the basin was warmer and moister than that in recent times. Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m, forest at an elevation of 2,550-2,750 m, steppe at an elevation of 1,550-2,150 m and desert steppe below 1,550 m. The upstream, midstream, downstream and average annual runoff of the mid-Holocene in the basin were 16.76×108 m3, 22.86×108 m3, 9.00×108 m3 and 16.20×108 m3 respectively, compared to 15.61×108 m3 of modern annual runoff. Also, the area of terminal paleo-lake in the mid-Holocene was 628 km2. Thus, this study provides a new quantitative method for paleo-hydrological simulation.

• Simulation and prediction of monthly accumulated runoff, based on several neural network models under poor data availability
• JianPing Qian,JianPing Zhao,Yi Liu,XinLong Feng,DongWei Gui
• DOI:10.3724/SP.J.1226.2018.00468
• 2018, 10 (6): 468–481 Abstract (35) HTML (3) PDF (662 KB) (26)
• Most previous research on areas with abundant rainfall shows that simulations using rainfall-runoff modes have a very high prediction accuracy and applicability when using a back-propagation (BP), feed-forward, multilayer perceptron artificial neural network (ANN). However, in runoff areas with relatively low rainfall or a dry climate, more studies are needed. In these areas—of which oasis-plain areas are a particularly good example—the existence and development of runoff depends largely on that which is generated from alpine regions. Quantitative analysis of the uncertainty of runoff simulation under climate change is the key to improving the utilization and management of water resources in arid areas. Therefore, in this context, three kinds of BP feed-forward, three-layer ANNs with similar structure were chosen as models in this paper. Taking the oasis–plain region traverse by the Qira River Basin in Xinjiang, China, as the research area, the monthly accumulated runoff of the Qira River in the next month was simulated and predicted. The results showed that the training precision of a compact wavelet neural network is low; but from the forecasting results, it could be concluded that the training algorithm can better reflect the whole law of samples. The traditional artificial neural network (TANN) model and radial basis-function neural network (RBFNN) model showed higher accuracy in the training and prediction stage. However, the TANN model, more sensitive to the selection of input variables, requires a large number of numerical simulations to determine the appropriate input variables and the number of hidden-layer neurons. Hence, The RBFNN model is more suitable for the study of such problems. And it can be extended to other similar research arid-oasis areas on the southern edge of the Kunlun Mountains and provides a reference for sustainable water-resource management of arid-oasis areas.

• How changes of groundwater level affect the desert riparian forest ecosystem in the Ejina Oasis, Northwest China
• HaiYang Xi,JingTian Zhang,Qi Feng,Lu Zhang,JianHua Si,TengFei Yu
• DOI:10.3724/SP.J.1226.2019.00062
• 2019, 11 (1): 62–80 Abstract (59) HTML (1) PDF (10223 KB) (25)
• Groundwater is a key factor controlling the growth of vegetation in desert riparian systems. It is important to recognise how groundwater changes affect the riparian forest ecosystem. This information will not only help us to understand the ecological and hydrological process of the riparian forest but also provide support for ecological recovery of riparian forests and water-resources management of arid inland river basins. This study aims to estimate the suitability of the Water Vegetation Energy and Solute Modelling (WAVES) model to simulate the Ejina Desert riparian forest ecosystem changes, China, to assess effects of groundwater-depth change on the canopy leaf area index (LAI) and water budgets, and to ascertain the suitable groundwater depth for preserving the stability and structure of desert riparian forest. Results demonstrated that the WAVES model can simulate changes to ecological and hydrological processes. The annual mean water consumption of a Tamarix chinensis riparian forest was less than that of a Populus euphratica riparian forest, and the canopy LAI of the desert riparian forest should increase as groundwater depth decreases. Groundwater changes could significantly influence water budgets for T. chinensis and P. euphratica riparian forests and show the positive and negative effects on vegetation growth and water budgets of riparian forests. Maintaining the annual mean groundwater depth at around 1.7?2.7 m is critical for healthy riparian forest growth. This study highlights the importance of considering groundwater-change impacts on desert riparian vegetation and water-balance applications in ecological restoration and efficient water-resource management in the Heihe River Basin.

• Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan
• Javed Hassan, Rijan Bhakta Kayastha, Ahuti Shrestha, Iram Bano, Sayed Hammad Ali, Haleem Zaman Magsi
• DOI:10.3724/SP.J.1226.2017.00511
• 2017, 9 (6): 511–524 Abstract (78) PDF (2396 KB) (24)
• The high mountains of Hindu-Kush Karakoram and Himalaya (HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data (r=0.88). Local temperature lapse rate of 0.0075 ℃/m is used. 2 ℃ critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration (0.86% and 0.90%) and validation (0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios. Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.
• Effects of intercropping on rhizosphere soil microorganisms and root exudates of Lanzhou lily (Lilium davidii var. unicolor)
• CuiPing Hua, YaJun Wang, ZhongKui Xie, ZhiHong Guo, YuBao Zhang, Yang Qiu, Le Wang
• DOI:10.3724/SP.J.1226.2018.00159
• 2018, 10 (2): 159–168 Abstract (32) PDF (1727 KB) (23)
• Both yield and quality of Lanzhou lily (Lilium davidii var. unicolor) are seriously affected by continuous cropping. We attempted to understand the effects of intercropping on the obstacles associated with continuous cropping of Lanzhou lily (Lilium davidii var. unicolor). The changes of rhizosphere microbial biomass and diversity in interplanting and monoculturing systems were studied by using the Illumina HiSeq sequencing technique. The contents and composition of lily root exudates were measured by gas chromatography–mass spectrometer (GC–MS). The intercropping results of Lanzhou lily showed: (1) There was no difference in the composition of the rhizosphere soil microbes at the phylum level, but the relative abundance of the microbes decreased; and the relative abundance of harmful fungi such as Fusarium sp. increased. The relative abundance of Pleosporales sp. and other beneficial bacteria were reduced. After OTU (operational taxonomic unit) clustering, there were some beneficial bacteria, such as Chaetomium sp., in the lily rhizosphere soil in the interplanting system that had not existed in the single-cropping system. We did not find harmful bacteria that had existed in the single-cropping systm in the rhizosphere soil of interplanting system. The above results indicated that the changes of relative abundance of soil fungi and bacteria in lily rhizosphere soil was not conducive to improving the ecological structure of rhizosphere soil microbes. At the same time, the microbial composition change is very complex—beneficial and yet inadequate at the same time. (2) Root exudates provide a matrix for the growth of microorganisms. Combined with the detection of root exudates, the decrease in the composition of the root exudates of the lily was probably the reason for the decrease of the relative abundance of microbes after intercropping. At the same time, the decrease of the relative content of phenolic compounds, which inhibit the growth of microorganisms, did not increase the relative content of rhizosphere soil microorganisms. Changes in amino acids and total sugars may be responsible for the growth of Fusarium sp.. The results showed that the intercropping pattern did not noticeably alleviate the obstacle to continuous cropping of Lanzhou lily, and the change of microbial biomass and diversity was even unfavorable. However, the emergence of some beneficial bacteria, the disappearance of harmful fungi, and other changes with intercropping are in favor of alleviation of obstacles to continuous cropping of Lanzhou lily.
• Research on pile performance and state-of-the-art practice in cold regions
• JianKun Liu, TengFei Wang, Zhi Wen
• DOI:10.3724/SP.J.1226.2018.00001
• 2018, 10 (1): 1–11 Abstract (46) PDF (3429 KB) (22)
• A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows: (1) creep tests and bearing capacity, (2) frost-jacking hazards, (3) laterally loaded piles, (4) dynamic responses, (5) refreezing due to concrete-hydration heat, and (6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.
• The analysis of heat and water fluxes in frozen silty soil
• DaHu Rui,Ming Lu,Kunio Watanabe,Jun Zhang
• DOI:10.3724/SP.J.1226.2019.00021
• 2019, 11 (1): 21–28 Abstract (51) HTML (6) PDF (2368 KB) (22)
• In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established. The numerical model was realized in COMSOL Multiphysics software, and simulation results are compared with the experimental results of Watanabe and Wake (2008) to verify the effectiveness of the model. Through the calculation, we can obtain the dynamic changes of heat and water fluxes, thermal and hydrological properties, matric potential and temperature gradient in unsaturated freezing soil; and these variables are unmeasurable in practice.

• Effects of freeze−thaw cycle and dry−wet alternation on slope stability
• YaLing Chou,LiYuan Sun,BaoAn Li,XiaoLi Wang
• DOI:10.3724/SP.J.1226.2019.00159.
• 2019, 11 (2): 159–172 Abstract (24) HTML (1) PDF (31417 KB) (22)
• The typical loess on high slopes along the BaoLan High-speed Rail, China, was selected as the research object. The influence of the freeze?thaw cycle and dry?wet alternation on the shear-strength parameters of the unsaturated loess was investigated by laboratory experimental methods. Moreover, the temperature field, seepage field, and stability of slopes with different gradients were simulated under the effect of the freeze?thaw cycle and dry?wet alternation by using the geotechnical analysis software Geo-Studio. The research results showed (1) when the freeze?thaw cycle was repeated on the slope, with the frozen depth increasing, the melted depth did the same; besides, the closed loop of isotherms formed on the slope; (2) under the action of dry?wet circulation, the negative pore-water pressure and volumetric water content showed an upward tendency. However, owing to the different slope gradients, rainfall infiltration was not the same. As time went by, the differences of the negative pore-water pressure and volumetric water content between the slopes of different gradients continued to increase; (3) with the freeze?thaw cycle and dry?wet alternation increasing, the slope-safety factor decreased. Especially in the early period, the slope-safety factor changed remarkably. For slopes undergoing freeze?thaw action, the slope-safety factor was negatively correlated with the gradient. However, with regard to slopes undergoing dry?wet alternation, the result became more complex because the slope-safety factor was related to both seepage strength and slope grade. Accordingly, further research is needed to study the effect of seepage strength and slope grade on the stability of loess slopes.

• MODIS observed snow cover variations in the Aksu River Basin, Northwest China
• Jing Li,ShiYin Liu,Qiao Liu
• DOI:10.3724/SP.J.1226.2019.00208.
• 2019, 11 (3): 208–217 Abstract (28) HTML (2) PDF (2915 KB) (22)
• A major proportion of discharge in the Aksu River is contributed from snow- and glacier-melt water. It is therefore essential to understand the cryospheric dynamics in this area for water resource management. The MODIS MOD10A2 remote-sensing database from March 2000 to December 2012 was selected to analyze snow cover changes. Snow cover varied significantly on a temporal and spatial scale for the basin. The difference of the maximum and minimum Snow Cover Fraction (SCF) in winter exceeded 70%. On average for annual cycle, the characteristic of SCF is that it reached the highest value of 53.2% in January and lowest value of 14.7% in July and the distributions of SCF along with elevation is an obvious difference between the range of 3,000 m below and 3,000 m above. The fluctuation of annual average snow cover is strong which shows that the spring snow cover was on the trend of increasing because of decreasing temperatures for the period of 2000-2012. However, temperature in April increased significantly which lead to more snowmelt and a decrease of snow cover. Thus, more attention is needed for flooding in this region due to strong melting of snow.

• Variation and relationship between soil moisture and environmental factors in the source region of the Yangtze River from 2005 to 2016
• LingLing Song,ZongJie Li,Qing Tian,LieFu Wang,Jing He,RuiFeng Yuan,Juan Gui,BaiJuan Zhang,YueMin Lv
• DOI:10.3724/SP.J.1226.2019.00184.
• 2019, 11 (3): 184–193 Abstract (33) HTML (4) PDF (4518 KB) (21)
• This study analyzed soil moisture, soil erosion, and vegetation in the source region of the Yangtze River from 2005 to 2016. We found that soil moisture showed an increasing trend from 2005 to 2009 but decreased from 2009 to 2016. The surface soil moisture was severely affected by seasonal changes in the source region of the Yangtze River, especially in the soil from 0 to 40 cm. However, seasonal variation of soil moisture deeper than 40 cm was different from that in the upper layer. Soil moisture below 40 cm wasn't affected by the seasonal variation. Soil moisture from 0 to 50 cm and the average thickness of wind deposition showed a positive correlation in the study area from 2005 to 2016. For environmental protection in the source region of the Yangtze River, wind deposition played a role in water retention. Similarly, a positive correlation also existed between the average thickness of wind erosion and soil moisture. Deep-soil moisture was the key factor for vegetation structure on the Qinghai-Tibet Plateau. The results are also helpful for further understanding the variation of soil moisture on the Tibetan Plateau and providing a scientific basis for effectively protecting and controlling the ecological environment in the future.

• Local meteorology in a northern Himalayan valley near Mount Everest and its response to seasonal transitions
• FangLin Sun,YaoMing Ma,ZeYong Hu
• DOI:10.3724/SP.J.1226.2018.00493
• 2018, 10 (6): 493–501 Abstract (37) HTML (4) PDF (30528 KB) (20)
• An automatic weather station (AWS) has been installed at the Qomolangma Station of the China Academy of Sciences (QOMS) since 2005, in a northern Himalayan valley near Mount Everest, with an altitude of 4,270 m a.s.l.. Nine years of meteorological records (2006–2014) from the automatic weather station (AWS) were analyzed in this study, aiming to understand the response of local weather to the seasonal transition on the northern slopes of Mount Everest, with consideration of the movement of the subtropical jet (STJ) and the onset of the Indian Summer Monsoon (ISM). We found: (1) Both the synoptic circulation and the orography have a profound influence on the local weather, especially the local circulation. (2) Southwesterly (SW) and southeasterly (SE) winds prevail alternately at QOMS in the afternoon through the year. The SW wind was driven by the STJ during the non-monsoon months, while the SE was induced by the trans-Himalayan flow through the Arun Valley, a major valley to the east of Mount Everest, under a background of weak westerly winds aloft. (3) The response of air temperature (T) and specific humidity (q) to the monsoon onset is not as marked as that of the nearsurface winds. The q increases gradually and reaches a maximum in July when the rainy period begins. (4) The alternation between the SW wind at QOMS and the afternoon SE wind in the pre-monsoon season signals the northward shift of the STJ and imminent monsoon onset. The average interval between these two events is 14 days.

• Effect of slow-release iron fertilizer on iron-deficiency chlorosis, yield and quality of Lilium davidii var. unicolor in a two-year field experiment
• Yang Qiu,ZhongKui Xie,XinPing Wang,YaJun Wang,YuBao Zhang,YuHui He,WenMei Li,WenCong Lv
• DOI:10.3724/SP.J.1226.2018.00421
• 2018, 10 (5): 421–427 Abstract (38) HTML (1) PDF (4283 KB) (19)
• Iron deficiency chlorosis of Lilium davidii var. unicolor is often the case in practice in alkaline soils of northwest region of China. It is difficult to control iron chlorosis because of high cost and short effective work time of conventional iron fertilizers. In this study, a 2-year field experiment was conducted to evaluate the effects of two slow-release fertilizers on the suppression of iron deficiency chlorosis, soil chemical properties, and the yield and quality of L. davidii var. unicolor. Results show that both coated slow-release iron fertilizers and embedded slow-release iron fertilizer effectively controlled iron-deficiency chlorosis. The application of slow-release iron fertilizers significantly increased plant height and chlorophyll content of L. davidii var. unicolor at different growth stages. Furthermore, coated iron fertilizer application significantly increased starch, protein, soluble sugar and vitamin C content of L. davidii var. unicolor, and it also significantly improved total amino acid content, with increases in essential amino acids (Trp, Leu, Lys, Phe, Val, and Thr contents) and in nonessential amino acids (Asp, Glu, Cit, Ihs, Acc, Ala, Pro, and Cys contents). It was concluded that application of coated slow-release iron fertilizer could be a promising option for suppression of iron deficiency chlorosis and deserves further study.

• Contrasting vegetation changes in dry and humid regions of the Tibetan Plateau over recent decades
• RuiQing Li,YanHong Gao,DeLiang Chen,YongXin Zhang,SuoSuo Li
• DOI:10.3724/SP.J.1226.2018.00482
• 2018, 10 (6): 482–492 Abstract (37) HTML (4) PDF (544 KB) (19)
• An overall greening over the Tibetan Plateau (TP) in recent decades has been established through analyses of remotely sensed Normalized Difference Vegetation Index (NDVI), though the regional pattern of the changes and associated drivers remain to be explored. This study used a satellite Leaf Area Index (LAI) dataset (the GLASS LAI dataset) and examined vegetation changes in humid and arid regions of the TP during 1982–2012. Based on distributions of the major vegetation types, the TP was divided roughly into a humid southeastern region dominated by meadow and a dry northwestern region covered mainly by steppe. It was found that the dividing line between the two regions corresponded well with the lines of mean annual precipitation of 400 mm and the mean LAI of 0.3. LAI=0.3 was subsequently used as a threshold for investigating vegetation type changes at the interanual and decadal time scales: if LAI increased from less than 0.3 to greater than 0.3 from one time period to the next, it was regarded as a change from steppe to meadow, and vice versa. The analysis shows that changes in vegetation types occurred primarily around the dividing line of the two regions, with clear growth (reduction) of the area covered by meadow (steppe), in consistency with the findings from using another independent satellite product. Surface air temperature and precipitation (diurnal temperature range) appeared to contribute positively (negatively) to this change though climate variables displayed varying correlation with LAI for different time periods and different regions.

• Holocene lake carbon sequestration, hydrological status and vegetation change, China
• LingMei Xu,Yu Li,WangTing Ye,XinZhong Zhang,YiChan Li,YuXin Zhang
• DOI:10.3724/SP.J.1226.2019.00295.
• 2019, 11 (4): 295–326 Abstract (15) HTML (2) PDF (12602 KB) (19)
• Lakes have received considerable attention as long-term sinks for organic carbon (C) at regional and global scales. Previous studies have focused on assessment and quantification of carbon sinks, and few have worked on the relationship between millennial-scale lake C sequestration, hydrological status and vegetation, which has important scientific significance in improving our understanding of lake C stocks and storage mechanisms. Here, we present a comprehensive study of pollen records, organic geochemical proxies, lake-level records, sediment accumulation rate (SAR) and organic C accumulation rate (CAR) in China since the Holocene. We also include numerical climate classification and lake-level simulations, to investigate variations of lake C sequestration, hydrological status and vegetation during the Holocene. Results indicate that the evolution of lake C accumulation showed an out-of-phase relationship with hydrological status and vegetation in China. Lake C accumulation exhibited an overall trend of increasing from the early to late Holocene in response to gradually increasing terrestrial organic matter input. However, China as a whole experienced the densest vegetation cover in the middle Holocene, corresponding to the mid-Holocene optimum of a milder and wetter climate. Optimal hydrological conditions were asynchronous in China; for example, early Holocene in Asian monsoon dominated areas, and middle Holocene in westerlies controlled regions. Our synthesis indicated that climate change was the main factor controlling the long-term variability in lake C accumulation, hydrologic conditions, as well as vegetation, and human influences were usually superimposed on the natural trends.

• Holocene climatic change reconstructed from trace elements of an aeolian deposit in the southeastern Mu Us Desert, northern China
• Bing Liu,HeLing Jin,LiangYing Sun,WenPing Xue,ZhenYu Liu
• DOI:10.3724/SP.J.1226.2019.00126.
• 2019, 11 (2): 126–138 Abstract (33) HTML (1) PDF (10837 KB) (18)
• In semi-arid and arid desert regions of northern China, aeolian deposits document the framework variation of an Asian monsoon during the late Quaternary. However, there is still a lack of detailed data pertaining to Holocene Asian monsoonal variation especial in the modern Asian summer monsoonal boundary belt. In this study, we reconstructed Holocene millennial-scale climatic changes in the Mu Us Desert, northern China, through systematic analysis of the variation of trace elements (324 samples) in different lithological units of the palaeosol-aeolian sand deposit, in combination with 14C and OSL chronology. Statistical results, correlation and clustering analysis indicate that the high content of 11 trace elements (V, Y, Cr, Nb, P, Mn, Cu, Zr, As, Ni and Rb, represented by P) and lower Sr content corresponding to periods of palaeosol development, marked increase of vegetation, weathering degree, and enhanced Asian summer monsoonal strength. In contrast, their opposed variation are coincident with accumulated aeolian sand layers, implying weaker summer monsoons and less geochemical weathering and degraded vegetation. These associations can be considered as signaling regional humid and dry changes of the Holocene environment. Accordingly, relatively arid conditions dominated the region before 7.2 ka, and there was an optimal humid climate in 7.2?4.6 ka. Afterwards, the climate became obviously dry, accompanied with several cycles of relatively wet and dry, such as relatively wet intervals around 4.1?3.7 ka, 3.5?3.3 ka and 2.5 ka. In addition, six millennial-scale dry events were recorded, and these events were consistent with weaker Asian summer monsoonal intervals in low latitudes, declined palaeosol development and precipitation in middle latitudes, as well as increased winter monsoon and periodic ice-rafting events in high latitudes of the Northern Hemisphere, within limits of accuracy of existing dating ages. This possibly suggests a noteworthy synchronism between millennial-scale climatic changes in this region and on a global scale.

• A landscape management analysis framework and its preliminary application in Ejina Oasis, Northwest China
• YouHua Ran,Yan Zhao
• DOI:10.3724/SP.J.1226.2019.00239.
• 2019, 11 (3): 239–247 Abstract (24) HTML (0) PDF (7491 KB) (18)
• The implementation of integrated landscape management to support local and regional human well-being is crucial in arid regions, but its application to date is very limited. Although analytical frameworks have been established to maximize ecosystem services via trade-offs between different landscape configurations, consumption factors such as water resources are rarely and weakly considered in such frameworks. In this paper, an improved integrated landscape-management analysis framework, called the Consumption-integrated Landscape Management to Ecosystem Service (CLMES), is proposed. In this framework, consumption factors are integrated at the same level as ecosystem services. The improved analytical framework is then used to assess and optimize landscape design in the Ejina Oasis, an extremely arid region in western China. Three landscape conditions (past, current, and future) are evaluated, based on the CLMES. Our results indicate that the Heihe River water-allocation program effectively promoted ecosystem services in the Ejina Oasis from 2000 to 2011. However, the excessive expansion of cropland led to a slight decline in habitat quality. An optimized landscape configuration and policy suggestions are proposed, which may be beneficial to the improvement of total water-use efficiency, oasis stability, and resilience of the ecological-social system in the Ejina Oasis.

• Comparison of precipitation products to observations in Tibet during the rainy season
• Zhuo Ga,Za Dui,Duodian Luozhu,Jun Du
• DOI:10.3724/SP.J.1226.2018.00392
• 2018, 10 (5): 392–403 Abstract (25) HTML (5) PDF (7662 KB) (17)
• Precipitation is an important component of global water and energy transport and a major aspect of climate change. Due to the scarcity of meteorological observations, the precipitation climate over Tibet has been insufficiently documented. In this study, the distribution of precipitation during the rainy season over Tibet from 1980 to 2013 is described on monthly to annual time scales with meteorological observations. Furthermore, four precipitation products are compared to observations over Tibet. These datasets include products derived from the Asian Precipitation-Highly-Resolved Observational Data (APHRO), the Global Precipitation Climatology Centre (GPCC), the University of Delaware (UDel), and the China Meteorological Administration (CMA). The error, relative error, standard deviation, root-mean-square error, correlations and trends between these products for the same period are analyzed with in situ precipitation during the rainy season from May to September. The results indicate that these datasets can broadly capture the temporal and spatial precipitation distribution over Tibet. The precipitation gradually increases from northwest to southeast. The spatial precipitation in GPCC and CMA are similar and positively correlated to observations. Areas with the largest deviations are located in southwestern Tibet along the Himalayas. The APHRO product underestimates, while the UDel, GPCC, and CMA datasets overestimates precipitation on the basis of monthly and inter-annual variation. The biases in GPCC and CMA are smaller than those in APHRO and UDel with a mean relative error lower than 10% during the same periods. The linear trend of precipitation indicates that the increase in precipitation has accelerated extensively during the last 30 years in most regions of Tibet. The CMA generally achieves the best performance of these four precipitation products. Data uncertainty in Tibet might be caused by the low density of stations, complex topography between the grid points and stations, and the interpolation methods, which can also produce an obvious difference between the gridded data and observations.

• Increase in medium-size rainfall events will enhance the C-sequestration capacity of biological soil crusts
• CuiHua Huang,Fei Peng,Itaru Shibata,Jun Luo,Xian Xue,Kinya Akashi,Atsushi Tsunekawa,Tao Wang
• DOI:10.3724/SP.J.1226.2019.00081
• 2019, 11 (1): 81–92 Abstract (45) HTML (2) PDF (3973 KB) (17)
• Biological soil crusts (BSCs) play important roles in the carbon (C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs (the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount (SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae?lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen?moss crust on the windward. Even a small rainfall (1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and -emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5?10 mm rainfall events in the desert?oasis transitional zone.

• Glacier mapping based on Chinese high-resolution remote sensing GF-1 satellite and topographic data
• LiLi Yan,Jian Wang
• DOI:10.3724/SP.J.1226.2019.00218.
• 2019, 11 (3): 218–225 Abstract (22) HTML (1) PDF (8415 KB) (17)
• The precise glacier boundary is a fundamental requirement for glacier inventory, the assessment of climate change and water management in remote mountain areas. However, some glaciers in mountain areas are covered by debris. The high spatial resolution images bring opportunities in mapping debris-covered glaciers. To discuss the capability of Chinese GaoFen-1 satellite lacking the short wave infrared band and thermal infrared band in mapping glaciers, this study distinguished supraglacial terrain from surrounding debris by combining GaoFen-1 (GF-1) wide-field-view (WFV) images, the ratio of the thermal infrared imagery and morphometric parameters (DEM and slope) with 30 m resolution. The overall accuracy of 90.94% indicated that this method was effective for mapping supraglacial terrain in mountain areas. Comparing this result with the combination of GF-1 WFV and low-resolution morphometric parameters shows that a high-quality DEM and the thermal infrared band enhanced the accuracy of glacier mapping especially debris-covered ice in steep terrain. The user's and producer's accuracies of glacier area were also improved from 89.67% and 85.95% to 92.83% and 90.34%, respectively. GF data is recommended for mapping heavily debris-covered glaciers and will be combined with SAR data for future studies.

• Stem radial growth indicate the options of species, topography and stand management for artificial forests in the western Loess Plateau, China
• ShengChun Xiao,XiaoMei Peng,QuanYan Tian,Gong Zhu
• DOI:10.3724/SP.J.1226.2019.00226.
• 2019, 11 (3): 226–238 Abstract (22) HTML (0) PDF (4802 KB) (17)
• An understanding of the differences in artificial forest between tree species, slope aspects, and management options in arid environments is fundamentally important for efficient management of these artificial systems; however, few studies have quantified the spatial and temporal differences in stem radial growth of trees in the arid western Loess Plateau of China. Using dendrochronology, we assessed the growth of three woody species (the native shrub Reaumuria soongorica, the exotic shrub Tamarix ramosissima and tree Platycladus orientalis) by measuring the annual stem radial increment. We also describe the long-term growth trends and responses to climatic factors on slopes with different aspects during periods with and without irrigation. We found that precipitation during the main growing season was significantly positively correlated with ring growth for all three species and both slope aspects. In addition, supplemental water (e.g., irrigation, rainwater harvesting) greatly relieved drought stress and promoted radial growth. Our results suggest that as the main afforestation species in the Loess Plateau used for soil and water conservation, P. orientalis is more suitable than T. ramosissima under rain-fed conditions. However, a landscape that combined a tree (P. orientalis) with a shrub (R. soongorica) and grassland appears likely to represent the best means of ecological restoration in the arid western Loess Plateau.

• Study of thermal properties of supraglacial debris and degree-day factors on Lirung Glacier, Nepal
• Mohan Bahadur Chand,Rijan Bhakta Kayastha
• DOI:10.3724/SP.J.1226.2018.00357
• 2018, 10 (5): 357–368 Abstract (187) HTML (23) PDF (4797 KB) (115)
• The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.

• Analysis of vegetation changes and dominant factors on the Qinghai-Tibet Plateau, China
• HongWei Wang,Yuan Qi,ChunLin Huang,XiaoYing Li,XiaoHong Deng,JinLong Zhang
• DOI:10.3724/SP.J.1226.2019.00150.
• 2019, 11 (2): 150–158 Abstract (44) HTML (5) PDF (34922 KB) (66)
• This research was undertaken to clarify the characteristics of vegetation change and its main influencing factors on the Qinghai-Tibet Plateau. Using the greenness rate of change (GRC) and correlation factors, we analyzed the trend of vegetation change and its dominant factors from 2000 to 2015. The results indicate that the vegetation tended to improve from 2000 to 2015 on the Qinghai-Tibet Plateau, with the improved area accounting for 39.93% of the total; and the degraded area accounting for 19.32%. The areas of degraded vegetation are mainly concentrated in the low-relief and intermediate-relief mountains of the high-altitude and extremely high-altitude areas on the Qinghai-Tibet Plateau, as the vegetation characteristics are impacted by the terrain. Temperature and precipitation have obvious response mechanisms to vegetation growth, but the effects of precipitation and temperature on vegetation degradation are not significant over a short time frame. Overgrazing and population growth are the dominant factors of vegetation degradation on the Qinghai-Tibet Plateau.

• Stable isotopes reveal varying water sources of Caragana microphylla in a desert-oasis ecotone near the Badain Jaran Desert
• Hai Zhou,WenZhi Zhao,ZhiBin He,Heng Ren
• DOI:10.3724/SP.J.1226.2018.00458
• 2018, 10 (6): 458–467 Abstract (51) HTML (7) PDF (10064 KB) (54)
• Understanding the variation in a plant's water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios (δ18O) of xylem water of Caragana microphylla, precipitation, soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub. We found that the water sources of C. microphylla differed with the plant's ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer, the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.

• Review on simulation of land-surface processes on the Tibetan Plateau
• Rui Chen,MeiXue Yang,XueJia Wang,GuoNing Wan
• DOI:10.3724/SP.J.1226.2019.00093.
• 2019, 11 (2): 93–115 Abstract (48) HTML (9) PDF (9572 KB) (51)
• The Tibetan Plateau (TP) has powerful dynamics and thermal effects, which makes the interaction between its land and atmosphere significantly affect climate and environment in the regional or global area. By retrospecting the latest research progress in the simulation of land-surface processes (LSPs) over the past 20 years, this study discusses both the simulation ability of land-surface models (LSMs) and the modification of parameterization schemes from two perspectives, the models' applicability and improved parameterization schemes. Our review suggests that different LSMs can well capture the spatiotemporal variations of the physical quantities of LSPs; but none of them can be fully applied to the plateau, meaning that all need to be revised according to the characteristics specific to the TP. Avoiding the unstable iterative computation and determining the freeze?thaw critical temperature according to the thermodynamic equilibrium equation, the unreasonable freeze?thaw parameterization scheme can be improved. Due to the complex underlying surface of the TP, no parameterization scheme of roughness length can well simulate the various characteristics of the turbulent flux over the TP at different temporal scales. The uniform soil thermodynamic and hydraulic parameterization scheme is unreasonable when it is applied to the plateau, as a result of the strong soil heterogeneity. There is little research on the snow-cover process so far, and the improved scheme has no advantage over the original one due to the lack of some related physical processes. The constant interaction among subprocesses of LSPs makes the improvement of a multiparameterization scheme yield better simulation results. According to the review of existing research, adding high-quality observation stations, developing a parameterization scheme suitable for the special LSPs of the TP, and adjusting the model structures can be helpful to the simulation of LSPs on the TP.

• Characterization of landscape pattern based on land economic niche change: A case study in Ganzhou, Gansu Province, China
• HuaLi Tong, PeiJi Shi, XueBin Zhang, ZaiYan Li
• DOI:10.3724/SP.J.1226.2018.00261
• 2018, 10 (3): 261–270 Abstract (16) PDF (1614 KB) (48)
• Land use change has a profound impact on biodiversity and ecological processes, and is closely related to changes in landscape patterns. This paper introduces the theory and method of land economic niche into landscape ecology, which provides a new method for spatial characterization of urban and rural spatial landscape patterns. Based on this theory, this paper analyzes the landscape pattern of Ganzhou District by using Landsat images as data source in 1995, 2000, 2005, 2010 and 2015. We calculated the land economic niche by applying the niche potential theory. Combined with the theory of landscape ecology, we explored the effects of the land economic niche change on the landscape pattern at a county scale. The results show that economic niche of construction land, watershed and farmland increased during 1995-2015, and grassland declined significantly. The economic niche of farmland, construction land, watershed and grassland show a negative correlation with the number of patches (NP), fragmentation index (FN) and the fractal dimension index (FD), and had a positive correlation with the aggregation index (AI). There was no significant correlation between the forest land economic niche and landscape metrics. The change of land economic niche has a driving effect on the landscape pattern of the county, which can represent the economic development direction of Ganzhou District. The land economic niche is closely related to the landscape type which can directly obtain an economic benefit.
• Influence of frost weathering on the recession of surfaces of technogenic landforms in Yakutia
• Andrey E. Melnikov,Nikolay N. Grib
• DOI:10.3724/SP.J.1226.2019.00257.
• 2019, 11 (4): 257–266 Abstract (39) HTML (9) PDF (11754 KB) (46)
• The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.

• Spatial variations of Pb, As, and Cu in surface snow along the transect from the Zhongshan Station to Dome A, East Antarctica
• XingXing Jiang, ShuGui Hou, YuanSheng Li, HongXi Pang, Rong Hua, Mayewski Paul, Sneed Sharon, ChunLei An, Handley Michael, Ke Liu, WangBin Zhang
• DOI:10.3724/SP.J.1226.2018.00219
• 2018, 10 (3): 219–231 Abstract (23) PDF (1847 KB) (41)
• The spatial distributions of lead, arsenic, and copper (Pb, As, and Cu, respectively) in surface snow along the transect from the Zhongshan Station to Dome A, East Antarctica, are presented. The mean concentrations of Pb, As, and Cu are 1.04±1.56 pg/g, 0.39±0.08 pg/g, and 11.2±14.4 pg/g, respectively. It is estimated that anthropogenic contributions are dominant for Pb, As, and Cu. Spatially, Pb concentrations show an exponentially decreasing trend from the coast inland, while a moderate decreasing trend is observed for Cu concentrations in the coastal area (below 2,000 m above sea level (a.s.l.)). In the intermediate area (2,000-3,000 m a.s.l.), the concentrations and enrichment factors of all these elements show high variability due to the complicated characteristics of climate and environment. On the inland plateau (above 3,000 m a.s.l.), the high concentrations of As and Pb are induced by high deposition efficiency, the existence of polar stratospheric precipitation, and the different fraction deposition to East Antarctica. The extremely high concentrations with maximum values of 9.59 pg/g and 69.9 pg/g for Pb and Cu, respectively, are suggested to result mainly from local human activities at the station. Our results suggest that source, transport pathway, and deposition pattern, rather than distance from the coast or altitude, lead to the spatial distributions of Pb, As, and Cu; and it is further confirmed by spatial variations of the three metals deposited over the whole continent of Antarctica.
• Effects of N:P ratio of Artemisia ordosica on growth influenced by soil calcium carbonate
• YuTing Liang,XingDong He,JianTan Guo,HongJuan Jing
• DOI:10.3724/SP.J.1226.2018.00333
• 2018, 10 (4): 333–339 Abstract (28) HTML (2) PDF (1442 KB) (39)
• Soil calcium carbonate (CaCO3) has a strong solid phosphorus effect, and high content of CaCO3 can significantly reduce the effectiveness of soil phosphorus. To reveal the limiting effect of soil CaCO3 on the growth of plants on sand land and its mechanism of plant physiology, we performed pot experiments with a two-factor randomized block design and a three-factor orthogonal design for different soil CaCO3 content treatments using Artemisia ordosica seedlings. In the experiments, we surveyed plant height, aboveground biomass, root length and root weight and analyzed N, P concentrations and RNA content of the seedlings, and discussed the relationships between relative growth rate (RGR) of the seedlings and N:P ratio as well as RNA. Results show that, the RGRs of plant height and above-ground biomass of the seedlings decreased significantly with the increase of soil CaCO3 content, and those for root length and root weight decreased. The RGRs of plant height and above-ground biomass of the seedlings were significantly negatively correlated with leaf N:P ratios, but significantly positively correlated with leaf RNA content and leaf P concentrations. It can be seen that soil CaCO3 is a stress factor for the growth of A. ordosica seedlings, and the growth response of the seedlings under the influence of soil CaCO3 is in line with the Growth Rate Hypothesis.

• Intersection-pavement de-icing: comprehensive review and the state of the practice
• Yang ZhaoHui Joey
• DOI:10.3724/SP.J.1226.2019.00001
• 2019, 11 (1): 1–12 Abstract (63) HTML (12) PDF (925 KB) (35)
• Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application.

• Studies on eco-environmental change in source regions of the Yangtze and Yellow Rivers of China:present and future
• JianPing Yang
• DOI:10.3724/SP.J.1226.2019.00173.
• 2019, 11 (3): 173–183 Abstract (60) HTML (6) PDF (2405 KB) (34)
• The source regions of the Yangtze and Yellow Rivers are important in the field of eco-environmental change research in China because of its distinct alpine ecosystem and cryosphere environment. At present, there are three different concepts on the extent of source areas of the Yangtze and Yellow Rivers: hydrological, geographical, and eco-environmental. Over the past decades, annual average air temperature has warmed significantly; moreover, the temperature rise rate increases notably with increase of time of the data series. Annual precipitation has no obvious increase or decrease trend, and the climate has become warm and dry in the source regions. As a result, the cryosphere in the regions has shrunk significantly since 1960s. A warm and dry climate and changing cryosphere together induced a substantial declination of alpine wetlands, marked decrease in river runoff, significant degradation of alpine grassland, and a reduction of engineering stability. The ecological environment, however, has a tendency for restoration in the regions because the climate has become gradually warm and wet since 2000. Thus, studies on eco-environmental change is transforming from a single element to multidisciplinary integration. Climate change-cryopshere change-physical and socioeconomic impacts/risk-adaptation constitute a chain of multidisciplinary integration research.

• Numerical simulation of the climate effect of high-altitude lakes on the Tibetan Plateau
• YinHuan Ao,ShiHua Lyu,ZhaoGuo Li,LiJuan Wen,Lin Zhao
• DOI:10.3724/SP.J.1226.2018.00379
• 2018, 10 (5): 379–391 Abstract (44) HTML (5) PDF (5751 KB) (32)
• Lakes regulate the water and heat exchange between the ground and the atmosphere on different temporal and spatial scales. However, studies of the lake effect in the high-altitude Tibetan Plateau (TP) rarely have been performed until recently, and little attention has been paid to modelling of frozen lakes. In this study, the Weather Research and Forecasting Model (WRF v. 3.6.1) is employed to conduct three numerical experiments in the Ngoring Lake Basin (the original experiment, an experiment with a tuned model, and a no-lake experiment) to investigate the influences of parameter optimization on the lake simulation and of the high-altitude lake on the regional climate. After the lake depth, the roughness lengths, and initial surface temperature are corrected in the model, the simulation of the air temperature is distinctly improved. In the experiment using a tuned model, the simulated sensible-heat flux (H) is clearly improved, especially during periods of ice melting (from late spring to early summer) and freezing (late fall). The improvement of latent-heat flux (LE) is mainly manifested by the sharp increase in the correlation coefficient between simulation and observation, whereas the improvement in the average value is small. The optimization of initial surface temperature shows the most prominent effect in the first year and distinctly weakens after a freezing period. After the lakes become grassland in the model, the daytime temperature clearly increases during the freezing and melting periods; but the nocturnal cooling appears in other stages, especially from September to October. The annual mean H increases by 6.4 times in the regions of the Ngoring Lake and the Gyaring Lake, and the LE declines by 56.2%. The sum of H and LE increases from 71.2 W/m2 (with lake) to 84.6 W/m2 (no lake). For the entire simulation region, the sum of H and LE also increases slightly. After the lakes are removed, the air temperature increases significantly from June to September over the area corresponding to the two lakes, and an abnormal convergence field appears; at the same time, the precipitation clearly increases over the two lakes and surrounding areas.

• The establishment and development of Haloxylon ammodendron promotes salt accumulation in surface soil of arid sandy land
• YongZhong Su,TingNa Liu,JunQia Kong
• DOI:10.3724/SP.J.1226.2019.00116.
• 2019, 11 (2): 116–125 Abstract (35) HTML (3) PDF (1590 KB) (32)
• Haloxylon ammodendron, a representative C4 succulent xerophyte and salt-secreting plant, is widely used in vegetation reestablishment programs to stabilize shifting sand, and is one of the dominant shrubs in the shelter belt used to control desertification in the desert-oasis ecotone in northwestern China. In this study, we collected soil samples in an age sequence of 0-, 2-, 5-, 13-, 16-, 31-, and 39-year-old H. ammodendron plantations to assess the effects of the shrub on soil fertility and salinity. Results show that SOC and total N concentrations increased significantly with increasing plantation age and increased 5.95- (in the interspaces) to 9.05-fold (under the canopy) and 6.15- to 8.46-fold at the 0?5 cm depth at the 39-year-old plantation compared with non-vegetated sandy land. Simultaneously, H. ammodendron establishment and development resulted in significant salt accumulation in the surface layer. On average, total soil salt content at the 0?5 cm and 5?20 cm depth increased 16.8-fold and 4.4-fold, respectively, compared with non-vegetated sandy land. The increase of total salt derived mostly from the accumulation of SO $4 2 -$ , Ca2+ and Na+ with H. ammodendron development. The accumulation in salinity was more significant than the increase in fertility, suggesting that improved soil fertility did not limit the impact of salinization. The adverse effect of salt accumulation may result in H. ammodendron plantation degradation and impact community stability in the long run.

• Comparison of temperature extremes between Zhongshan Station and Great Wall Station in Antarctica
• AiHong Xie,ShiMeng Wang,YiCheng Wang,ChuanJin Li
• DOI:10.3724/SP.J.1226.2018.00369
• 2018, 10 (5): 369–378 Abstract (62) HTML (15) PDF (4839 KB) (29)
• Although temperature extremes have led to more and more disasters, there are as yet few studies on the extremes and many disagreements on temperature changes in Antarctica. Based on daily minimum, maximum, and mean air temperatures (Tmin, Tmax, Tmean) at Great Wall Station (GW) and Zhongshan Station (ZS), we compared the temperature extremes and revealed a strong warming trend in Tmin, a slight warming trend in Tmean, cooling in Tmax, a decreasing trend in the daily temperature range, and the typical characteristic of coreless winter temperature. There are different seasonal variabilities, with the least in summer. The continentality index and seasonality show that the marine air mass has more effect on GW than ZS. Following the terminology of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), we defined nine indices of temperature extremes, based on the Antarctic geographical environment. Extreme-warm days have decreased, while extreme-warm nights have shown a nonsignificant trend. The number of melting days has increased at GW, while little change at ZS. More importantly, we have found inverse variations in temperature patterns between the two stations, which need further investigation into the dynamics of climate change in Antarctica.

• Applying the AHP-FUZZY method to evaluate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau: a case study of Chaidaer-Muli Railway
• Wei Cao,Yu Sheng,Ji Chen,JiChun Wu
• DOI:10.3724/SP.J.1226.2018.00447
• 2018, 10 (6): 447–457 Abstract (54) HTML (10) PDF (480 KB) (29)
• This article attempts to investigate the measure effect of rubble roadbed engineering in permafrost regions of Qinghai-Tibet Plateau. As a case study, Chaidaer-Muli Railway is used to evaluate the measure effect of rubble roadbed engineering in permafrost regions. The AHP (Analytic Hierarchy Process) method is thus employed to establish the evaluation indicator system. The evaluation factor is selected by analyzing the mutual relation between the permafrost environment and roadbed engineering. Thus, a hierarchical structure model is established based on the selected evaluation indices. Each factor is weighted to determine the status in the evaluation system, and grading standards are built for providing a basis for the evaluation. Then, the fuzzy mathematical method is introduced to evaluate the measure effect of rubble roadbed engineering in permafrost regions along the Chadaer-Muli Railway. Results show that most of the permafrost roadbed is in a preferable condition (b) along the Chaidaer-Muli Railway due to rubble engineering measures. This proportion reaches to 86.1%. The proportion in good (a), general (c) and poor states (d) are 0.0%, 7.5% and 6.4%, respectively, in all the evaluation sections along the Chaidaer-Muli Railway. Ground-temperature monitoring results are generally consistent with AHP-FUZZY evaluation results. This means that the AHP-FUZZY method can be applied to evaluate the effect of rubble roadbed engineering measures in permafrost regions. The effect evaluation of engineering measures will provide timely and effective feedback information for further engineering design. The series of engineering measures will more effectively protect permafrost stability.

• The changing process and trend of ground temperature around tower foundations of Qinghai-Tibet Power Transmission line
• YanLi Xie, QiHao Yu, YanHui You, ZhongQiu Zhang, TingTao Gou
• DOI:10.3724/SP.J.1226.2019.00013
• 2019, 11 (1): 13–0020 Abstract (36) HTML (9) PDF (10529 KB) (29)
• After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission (QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons, while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.

• Shifts in community structure and function of ammonia-oxidizing archaea in biological soil crusts along a revegetation chronosequence in the Tengger Desert
• LiNa Zhao,XinRong Li,ShiWei Yuan,YuBing Liu
• DOI:10.3724/SP.J.1226.2019.00139.
• 2019, 11 (2): 139–149 Abstract (44) HTML (1) PDF (2660 KB) (29)
• Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea (AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts (BSCs) of desert ecosystems remain poorly understood. Here, we utilized Illumina MiSeq sequencing and microbial functional gene array (GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria (AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.

• Assessing the impacts of ecological-living-productive land changes on eco-environmental quality in Xining City on Qinghai-Tibet Plateau, China
• ZiYi Gao,HaiFeng Zhang,XiaoNan Yang,ZhiYuan Song
• DOI:10.3724/SP.J.1226.2019.00194.
• 2019, 11 (3): 194–207 Abstract (37) HTML (2) PDF (5003 KB) (29)
• The Ecological-living-productive land (ELPL) classification system was proposed in an effort to steer China’s land pattern to an ecological-centered path, with the development model shifting from a single function into more integrated multi-function land use. The focus is coordinating the man-land contradictions and developing an intensive, efficient and sustainable land use policy in an increasingly tense relationship between humans and nature. Driven by socioeconomic change and rapid population growth, many cities are undergoing urban sprawl, which involves the consumption of cropland and ecological land and threatens the ecological balance. This paper aims to quantitatively analyze the critical effects of ELPL changes on eco-environmental quality according to land use classification based on leading function of ecology, living and production from 1990 to 2015 with a case study of Xining City. Also, four future land use scenarios were simulated for 2030 using the Future Land Use Simulation (FLUS) model that couples human and natural effects. Our results show a decrease in productive land (PL) and an increase in ecological land (EL) and living land (LL) in Xining City. Forestry ecological land (FEL) covered the top largest proportion; agriculture productive land (APL) showed the greatest reduction and urban and rural living land (U-RLL) presented a dramatic increase. The eco-environmental quality improved in 1990-2010, mainly affected by the conversion of APL to FEL and GEL. However, the encroachment of U-RLL into APL, other ecological land (OEL) and FEL was the main contributor to the decline in eco-environmental quality in 2010-2015 as well as the primary reason for the increase area of lower-quality. The Harmonious Development (HD)-Scenario, characterized by a rational allocation of LL and PL and a better eco-environment, would have implications for planning and monitoring future management of ELPL, and may represent a valuable reference for local policy-makers.

• Altitude pattern of carbon stocks in desert grasslands of an arid land region
• Rong Yang,JunQia Kong,ZeYu Du,YongZhong Su
• DOI:10.3724/SP.J.1226.2018.00404
• 2018, 10 (5): 404–412 Abstract (28) HTML (3) PDF (4973 KB) (28)
• For estimating the altitude-distribution pattern of carbon stocks in desert grasslands and analyzing the possible mechanism for this distribution, a detailed study was performed through a series of field vegetation surveys and soil samplings from 90 vegetation plots and 45 soil profiles at 9 sites of the Hexi Corridor region, Northwestern China. Aboveground, belowground, and litter-fall biomass-carbon stocks ranged from 43 to 109, 23 to 64, and 5 to 20 g/m2, with mean values of 80.82, 44.91, and 12.15 g/m2, respectively. Soil-carbon stocks varied between 2.88 and 3.98 kg/m2, with a mean value of 3.43 kg/m2 in the 0–100-cm soil layer. Both biomass- and soil-carbon stocks had an increasing tendency corresponding to the altitudinal gradient. A significantly negative correlation was found between soil-carbon stock and mean annual temperature, with further better correlations between soil- and biomass-carbon stocks, and mean annual precipitation. Furthermore, soil carbon was found to be positively correlated with soil-silt and -clay content, and negatively correlated with soil bulk density and the volume percent of gravel. It can be concluded that variations in soil texture and climate condition were the key factors influencing the altitudinal pattern of carbon stocks in this desert-grassland ecosystem. Thus, by using the linear-regression functions between altitude and carbon stocks, approximately 4.18 Tg carbon were predicted from the 1,260 km2 of desert grasslands in the study area.

• Vulnerability and adaptation of an oasis social–ecological system affected by glacier change in an arid region of northwestern China
• JianPing Yang, Man Li, ChunPing Tan, HongJu Chen, Qin Ji
• DOI:10.3724/SP.J.1226.2019.00029
• 2019, 11 (1): 29–0040 Abstract (50) HTML (3) PDF (11448 KB) (27)
• The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis social-ecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis (SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-, medium-, and long-term adaptation initiatives are put forward in the article.

• A paleo-hydrological simulation experiment and its verification in an inland basin
• YuXin Zhang,Yu Li,XinZhong Zhang,ChengQi Zhang,WangTing Ye,Yuan Liu
• DOI:10.3724/SP.J.1226.2019.00267.
• 2019, 11 (4): 267–282 Abstract (21) HTML (4) PDF (3347 KB) (27)
• Hydrological circulation, as the most basic material cycle and active natural phenomenon on earth, exerts a significant influence on climate change. The mid-Holocene is an important period to better understand modern environmental change; however, little research has focused on its quantitative simulation of paleo-hydrological process. In this research, we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Basin to reconstruct the mid-Holocene environment and terminal paleo-lake area. Secondly, we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil, air, river and lacustrine sediments in the Shiyang River Basin, and combined the pollen records, as well as quantitatively reconstructed the millennial-scale vegetation zones. Finally, based on the land-cover adjustment results during the mid-Holocene, we successfully used the Soil and Water Assessment Tool (SWAT) model, a modern distributed hydrological watershed model, to simulate mid-Holocene runoff in the basin. Results show that the reconstructed climate in the basin was warmer and moister than that in recent times. Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m, forest at an elevation of 2,550-2,750 m, steppe at an elevation of 1,550-2,150 m and desert steppe below 1,550 m. The upstream, midstream, downstream and average annual runoff of the mid-Holocene in the basin were 16.76×108 m3, 22.86×108 m3, 9.00×108 m3 and 16.20×108 m3 respectively, compared to 15.61×108 m3 of modern annual runoff. Also, the area of terminal paleo-lake in the mid-Holocene was 628 km2. Thus, this study provides a new quantitative method for paleo-hydrological simulation.

• Simulation and prediction of monthly accumulated runoff, based on several neural network models under poor data availability
• JianPing Qian,JianPing Zhao,Yi Liu,XinLong Feng,DongWei Gui
• DOI:10.3724/SP.J.1226.2018.00468
• 2018, 10 (6): 468–481 Abstract (35) HTML (3) PDF (662 KB) (26)
• Most previous research on areas with abundant rainfall shows that simulations using rainfall-runoff modes have a very high prediction accuracy and applicability when using a back-propagation (BP), feed-forward, multilayer perceptron artificial neural network (ANN). However, in runoff areas with relatively low rainfall or a dry climate, more studies are needed. In these areas—of which oasis-plain areas are a particularly good example—the existence and development of runoff depends largely on that which is generated from alpine regions. Quantitative analysis of the uncertainty of runoff simulation under climate change is the key to improving the utilization and management of water resources in arid areas. Therefore, in this context, three kinds of BP feed-forward, three-layer ANNs with similar structure were chosen as models in this paper. Taking the oasis–plain region traverse by the Qira River Basin in Xinjiang, China, as the research area, the monthly accumulated runoff of the Qira River in the next month was simulated and predicted. The results showed that the training precision of a compact wavelet neural network is low; but from the forecasting results, it could be concluded that the training algorithm can better reflect the whole law of samples. The traditional artificial neural network (TANN) model and radial basis-function neural network (RBFNN) model showed higher accuracy in the training and prediction stage. However, the TANN model, more sensitive to the selection of input variables, requires a large number of numerical simulations to determine the appropriate input variables and the number of hidden-layer neurons. Hence, The RBFNN model is more suitable for the study of such problems. And it can be extended to other similar research arid-oasis areas on the southern edge of the Kunlun Mountains and provides a reference for sustainable water-resource management of arid-oasis areas.

• How changes of groundwater level affect the desert riparian forest ecosystem in the Ejina Oasis, Northwest China
• HaiYang Xi,JingTian Zhang,Qi Feng,Lu Zhang,JianHua Si,TengFei Yu
• DOI:10.3724/SP.J.1226.2019.00062
• 2019, 11 (1): 62–80 Abstract (59) HTML (1) PDF (10223 KB) (25)
• Groundwater is a key factor controlling the growth of vegetation in desert riparian systems. It is important to recognise how groundwater changes affect the riparian forest ecosystem. This information will not only help us to understand the ecological and hydrological process of the riparian forest but also provide support for ecological recovery of riparian forests and water-resources management of arid inland river basins. This study aims to estimate the suitability of the Water Vegetation Energy and Solute Modelling (WAVES) model to simulate the Ejina Desert riparian forest ecosystem changes, China, to assess effects of groundwater-depth change on the canopy leaf area index (LAI) and water budgets, and to ascertain the suitable groundwater depth for preserving the stability and structure of desert riparian forest. Results demonstrated that the WAVES model can simulate changes to ecological and hydrological processes. The annual mean water consumption of a Tamarix chinensis riparian forest was less than that of a Populus euphratica riparian forest, and the canopy LAI of the desert riparian forest should increase as groundwater depth decreases. Groundwater changes could significantly influence water budgets for T. chinensis and P. euphratica riparian forests and show the positive and negative effects on vegetation growth and water budgets of riparian forests. Maintaining the annual mean groundwater depth at around 1.7?2.7 m is critical for healthy riparian forest growth. This study highlights the importance of considering groundwater-change impacts on desert riparian vegetation and water-balance applications in ecological restoration and efficient water-resource management in the Heihe River Basin.

• Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan
• Javed Hassan, Rijan Bhakta Kayastha, Ahuti Shrestha, Iram Bano, Sayed Hammad Ali, Haleem Zaman Magsi
• DOI:10.3724/SP.J.1226.2017.00511
• 2017, 9 (6): 511–524 Abstract (78) PDF (2396 KB) (24)
• The high mountains of Hindu-Kush Karakoram and Himalaya (HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data (r=0.88). Local temperature lapse rate of 0.0075 ℃/m is used. 2 ℃ critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration (0.86% and 0.90%) and validation (0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios. Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.
• Effects of intercropping on rhizosphere soil microorganisms and root exudates of Lanzhou lily (Lilium davidii var. unicolor)
• CuiPing Hua, YaJun Wang, ZhongKui Xie, ZhiHong Guo, YuBao Zhang, Yang Qiu, Le Wang
• DOI:10.3724/SP.J.1226.2018.00159
• 2018, 10 (2): 159–168 Abstract (32) PDF (1727 KB) (23)
• Both yield and quality of Lanzhou lily (Lilium davidii var. unicolor) are seriously affected by continuous cropping. We attempted to understand the effects of intercropping on the obstacles associated with continuous cropping of Lanzhou lily (Lilium davidii var. unicolor). The changes of rhizosphere microbial biomass and diversity in interplanting and monoculturing systems were studied by using the Illumina HiSeq sequencing technique. The contents and composition of lily root exudates were measured by gas chromatography–mass spectrometer (GC–MS). The intercropping results of Lanzhou lily showed: (1) There was no difference in the composition of the rhizosphere soil microbes at the phylum level, but the relative abundance of the microbes decreased; and the relative abundance of harmful fungi such as Fusarium sp. increased. The relative abundance of Pleosporales sp. and other beneficial bacteria were reduced. After OTU (operational taxonomic unit) clustering, there were some beneficial bacteria, such as Chaetomium sp., in the lily rhizosphere soil in the interplanting system that had not existed in the single-cropping system. We did not find harmful bacteria that had existed in the single-cropping systm in the rhizosphere soil of interplanting system. The above results indicated that the changes of relative abundance of soil fungi and bacteria in lily rhizosphere soil was not conducive to improving the ecological structure of rhizosphere soil microbes. At the same time, the microbial composition change is very complex—beneficial and yet inadequate at the same time. (2) Root exudates provide a matrix for the growth of microorganisms. Combined with the detection of root exudates, the decrease in the composition of the root exudates of the lily was probably the reason for the decrease of the relative abundance of microbes after intercropping. At the same time, the decrease of the relative content of phenolic compounds, which inhibit the growth of microorganisms, did not increase the relative content of rhizosphere soil microorganisms. Changes in amino acids and total sugars may be responsible for the growth of Fusarium sp.. The results showed that the intercropping pattern did not noticeably alleviate the obstacle to continuous cropping of Lanzhou lily, and the change of microbial biomass and diversity was even unfavorable. However, the emergence of some beneficial bacteria, the disappearance of harmful fungi, and other changes with intercropping are in favor of alleviation of obstacles to continuous cropping of Lanzhou lily.
• Research on pile performance and state-of-the-art practice in cold regions
• JianKun Liu, TengFei Wang, Zhi Wen
• DOI:10.3724/SP.J.1226.2018.00001
• 2018, 10 (1): 1–11 Abstract (46) PDF (3429 KB) (22)
• A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows: (1) creep tests and bearing capacity, (2) frost-jacking hazards, (3) laterally loaded piles, (4) dynamic responses, (5) refreezing due to concrete-hydration heat, and (6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.
• The analysis of heat and water fluxes in frozen silty soil
• DaHu Rui,Ming Lu,Kunio Watanabe,Jun Zhang
• DOI:10.3724/SP.J.1226.2019.00021
• 2019, 11 (1): 21–28 Abstract (51) HTML (6) PDF (2368 KB) (22)
• In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established. The numerical model was realized in COMSOL Multiphysics software, and simulation results are compared with the experimental results of Watanabe and Wake (2008) to verify the effectiveness of the model. Through the calculation, we can obtain the dynamic changes of heat and water fluxes, thermal and hydrological properties, matric potential and temperature gradient in unsaturated freezing soil; and these variables are unmeasurable in practice.

• Effects of freeze−thaw cycle and dry−wet alternation on slope stability
• YaLing Chou,LiYuan Sun,BaoAn Li,XiaoLi Wang
• DOI:10.3724/SP.J.1226.2019.00159.
• 2019, 11 (2): 159–172 Abstract (24) HTML (1) PDF (31417 KB) (22)
• The typical loess on high slopes along the BaoLan High-speed Rail, China, was selected as the research object. The influence of the freeze?thaw cycle and dry?wet alternation on the shear-strength parameters of the unsaturated loess was investigated by laboratory experimental methods. Moreover, the temperature field, seepage field, and stability of slopes with different gradients were simulated under the effect of the freeze?thaw cycle and dry?wet alternation by using the geotechnical analysis software Geo-Studio. The research results showed (1) when the freeze?thaw cycle was repeated on the slope, with the frozen depth increasing, the melted depth did the same; besides, the closed loop of isotherms formed on the slope; (2) under the action of dry?wet circulation, the negative pore-water pressure and volumetric water content showed an upward tendency. However, owing to the different slope gradients, rainfall infiltration was not the same. As time went by, the differences of the negative pore-water pressure and volumetric water content between the slopes of different gradients continued to increase; (3) with the freeze?thaw cycle and dry?wet alternation increasing, the slope-safety factor decreased. Especially in the early period, the slope-safety factor changed remarkably. For slopes undergoing freeze?thaw action, the slope-safety factor was negatively correlated with the gradient. However, with regard to slopes undergoing dry?wet alternation, the result became more complex because the slope-safety factor was related to both seepage strength and slope grade. Accordingly, further research is needed to study the effect of seepage strength and slope grade on the stability of loess slopes.

• MODIS observed snow cover variations in the Aksu River Basin, Northwest China
• Jing Li,ShiYin Liu,Qiao Liu
• DOI:10.3724/SP.J.1226.2019.00208.
• 2019, 11 (3): 208–217 Abstract (28) HTML (2) PDF (2915 KB) (22)
• A major proportion of discharge in the Aksu River is contributed from snow- and glacier-melt water. It is therefore essential to understand the cryospheric dynamics in this area for water resource management. The MODIS MOD10A2 remote-sensing database from March 2000 to December 2012 was selected to analyze snow cover changes. Snow cover varied significantly on a temporal and spatial scale for the basin. The difference of the maximum and minimum Snow Cover Fraction (SCF) in winter exceeded 70%. On average for annual cycle, the characteristic of SCF is that it reached the highest value of 53.2% in January and lowest value of 14.7% in July and the distributions of SCF along with elevation is an obvious difference between the range of 3,000 m below and 3,000 m above. The fluctuation of annual average snow cover is strong which shows that the spring snow cover was on the trend of increasing because of decreasing temperatures for the period of 2000-2012. However, temperature in April increased significantly which lead to more snowmelt and a decrease of snow cover. Thus, more attention is needed for flooding in this region due to strong melting of snow.

• Variation and relationship between soil moisture and environmental factors in the source region of the Yangtze River from 2005 to 2016
• LingLing Song,ZongJie Li,Qing Tian,LieFu Wang,Jing He,RuiFeng Yuan,Juan Gui,BaiJuan Zhang,YueMin Lv
• DOI:10.3724/SP.J.1226.2019.00184.
• 2019, 11 (3): 184–193 Abstract (33) HTML (4) PDF (4518 KB) (21)
• This study analyzed soil moisture, soil erosion, and vegetation in the source region of the Yangtze River from 2005 to 2016. We found that soil moisture showed an increasing trend from 2005 to 2009 but decreased from 2009 to 2016. The surface soil moisture was severely affected by seasonal changes in the source region of the Yangtze River, especially in the soil from 0 to 40 cm. However, seasonal variation of soil moisture deeper than 40 cm was different from that in the upper layer. Soil moisture below 40 cm wasn't affected by the seasonal variation. Soil moisture from 0 to 50 cm and the average thickness of wind deposition showed a positive correlation in the study area from 2005 to 2016. For environmental protection in the source region of the Yangtze River, wind deposition played a role in water retention. Similarly, a positive correlation also existed between the average thickness of wind erosion and soil moisture. Deep-soil moisture was the key factor for vegetation structure on the Qinghai-Tibet Plateau. The results are also helpful for further understanding the variation of soil moisture on the Tibetan Plateau and providing a scientific basis for effectively protecting and controlling the ecological environment in the future.

• Local meteorology in a northern Himalayan valley near Mount Everest and its response to seasonal transitions
• FangLin Sun,YaoMing Ma,ZeYong Hu
• DOI:10.3724/SP.J.1226.2018.00493
• 2018, 10 (6): 493–501 Abstract (37) HTML (4) PDF (30528 KB) (20)
• An automatic weather station (AWS) has been installed at the Qomolangma Station of the China Academy of Sciences (QOMS) since 2005, in a northern Himalayan valley near Mount Everest, with an altitude of 4,270 m a.s.l.. Nine years of meteorological records (2006–2014) from the automatic weather station (AWS) were analyzed in this study, aiming to understand the response of local weather to the seasonal transition on the northern slopes of Mount Everest, with consideration of the movement of the subtropical jet (STJ) and the onset of the Indian Summer Monsoon (ISM). We found: (1) Both the synoptic circulation and the orography have a profound influence on the local weather, especially the local circulation. (2) Southwesterly (SW) and southeasterly (SE) winds prevail alternately at QOMS in the afternoon through the year. The SW wind was driven by the STJ during the non-monsoon months, while the SE was induced by the trans-Himalayan flow through the Arun Valley, a major valley to the east of Mount Everest, under a background of weak westerly winds aloft. (3) The response of air temperature (T) and specific humidity (q) to the monsoon onset is not as marked as that of the nearsurface winds. The q increases gradually and reaches a maximum in July when the rainy period begins. (4) The alternation between the SW wind at QOMS and the afternoon SE wind in the pre-monsoon season signals the northward shift of the STJ and imminent monsoon onset. The average interval between these two events is 14 days.

• Effect of slow-release iron fertilizer on iron-deficiency chlorosis, yield and quality of Lilium davidii var. unicolor in a two-year field experiment
• Yang Qiu,ZhongKui Xie,XinPing Wang,YaJun Wang,YuBao Zhang,YuHui He,WenMei Li,WenCong Lv
• DOI:10.3724/SP.J.1226.2018.00421
• 2018, 10 (5): 421–427 Abstract (38) HTML (1) PDF (4283 KB) (19)
• Iron deficiency chlorosis of Lilium davidii var. unicolor is often the case in practice in alkaline soils of northwest region of China. It is difficult to control iron chlorosis because of high cost and short effective work time of conventional iron fertilizers. In this study, a 2-year field experiment was conducted to evaluate the effects of two slow-release fertilizers on the suppression of iron deficiency chlorosis, soil chemical properties, and the yield and quality of L. davidii var. unicolor. Results show that both coated slow-release iron fertilizers and embedded slow-release iron fertilizer effectively controlled iron-deficiency chlorosis. The application of slow-release iron fertilizers significantly increased plant height and chlorophyll content of L. davidii var. unicolor at different growth stages. Furthermore, coated iron fertilizer application significantly increased starch, protein, soluble sugar and vitamin C content of L. davidii var. unicolor, and it also significantly improved total amino acid content, with increases in essential amino acids (Trp, Leu, Lys, Phe, Val, and Thr contents) and in nonessential amino acids (Asp, Glu, Cit, Ihs, Acc, Ala, Pro, and Cys contents). It was concluded that application of coated slow-release iron fertilizer could be a promising option for suppression of iron deficiency chlorosis and deserves further study.

• Contrasting vegetation changes in dry and humid regions of the Tibetan Plateau over recent decades
• RuiQing Li,YanHong Gao,DeLiang Chen,YongXin Zhang,SuoSuo Li
• DOI:10.3724/SP.J.1226.2018.00482
• 2018, 10 (6): 482–492 Abstract (37) HTML (4) PDF (544 KB) (19)
• An overall greening over the Tibetan Plateau (TP) in recent decades has been established through analyses of remotely sensed Normalized Difference Vegetation Index (NDVI), though the regional pattern of the changes and associated drivers remain to be explored. This study used a satellite Leaf Area Index (LAI) dataset (the GLASS LAI dataset) and examined vegetation changes in humid and arid regions of the TP during 1982–2012. Based on distributions of the major vegetation types, the TP was divided roughly into a humid southeastern region dominated by meadow and a dry northwestern region covered mainly by steppe. It was found that the dividing line between the two regions corresponded well with the lines of mean annual precipitation of 400 mm and the mean LAI of 0.3. LAI=0.3 was subsequently used as a threshold for investigating vegetation type changes at the interanual and decadal time scales: if LAI increased from less than 0.3 to greater than 0.3 from one time period to the next, it was regarded as a change from steppe to meadow, and vice versa. The analysis shows that changes in vegetation types occurred primarily around the dividing line of the two regions, with clear growth (reduction) of the area covered by meadow (steppe), in consistency with the findings from using another independent satellite product. Surface air temperature and precipitation (diurnal temperature range) appeared to contribute positively (negatively) to this change though climate variables displayed varying correlation with LAI for different time periods and different regions.

• Holocene lake carbon sequestration, hydrological status and vegetation change, China
• LingMei Xu,Yu Li,WangTing Ye,XinZhong Zhang,YiChan Li,YuXin Zhang
• DOI:10.3724/SP.J.1226.2019.00295.
• 2019, 11 (4): 295–326 Abstract (15) HTML (2) PDF (12602 KB) (19)
• Lakes have received considerable attention as long-term sinks for organic carbon (C) at regional and global scales. Previous studies have focused on assessment and quantification of carbon sinks, and few have worked on the relationship between millennial-scale lake C sequestration, hydrological status and vegetation, which has important scientific significance in improving our understanding of lake C stocks and storage mechanisms. Here, we present a comprehensive study of pollen records, organic geochemical proxies, lake-level records, sediment accumulation rate (SAR) and organic C accumulation rate (CAR) in China since the Holocene. We also include numerical climate classification and lake-level simulations, to investigate variations of lake C sequestration, hydrological status and vegetation during the Holocene. Results indicate that the evolution of lake C accumulation showed an out-of-phase relationship with hydrological status and vegetation in China. Lake C accumulation exhibited an overall trend of increasing from the early to late Holocene in response to gradually increasing terrestrial organic matter input. However, China as a whole experienced the densest vegetation cover in the middle Holocene, corresponding to the mid-Holocene optimum of a milder and wetter climate. Optimal hydrological conditions were asynchronous in China; for example, early Holocene in Asian monsoon dominated areas, and middle Holocene in westerlies controlled regions. Our synthesis indicated that climate change was the main factor controlling the long-term variability in lake C accumulation, hydrologic conditions, as well as vegetation, and human influences were usually superimposed on the natural trends.

• Holocene climatic change reconstructed from trace elements of an aeolian deposit in the southeastern Mu Us Desert, northern China
• Bing Liu,HeLing Jin,LiangYing Sun,WenPing Xue,ZhenYu Liu
• DOI:10.3724/SP.J.1226.2019.00126.
• 2019, 11 (2): 126–138 Abstract (33) HTML (1) PDF (10837 KB) (18)
• In semi-arid and arid desert regions of northern China, aeolian deposits document the framework variation of an Asian monsoon during the late Quaternary. However, there is still a lack of detailed data pertaining to Holocene Asian monsoonal variation especial in the modern Asian summer monsoonal boundary belt. In this study, we reconstructed Holocene millennial-scale climatic changes in the Mu Us Desert, northern China, through systematic analysis of the variation of trace elements (324 samples) in different lithological units of the palaeosol-aeolian sand deposit, in combination with 14C and OSL chronology. Statistical results, correlation and clustering analysis indicate that the high content of 11 trace elements (V, Y, Cr, Nb, P, Mn, Cu, Zr, As, Ni and Rb, represented by P) and lower Sr content corresponding to periods of palaeosol development, marked increase of vegetation, weathering degree, and enhanced Asian summer monsoonal strength. In contrast, their opposed variation are coincident with accumulated aeolian sand layers, implying weaker summer monsoons and less geochemical weathering and degraded vegetation. These associations can be considered as signaling regional humid and dry changes of the Holocene environment. Accordingly, relatively arid conditions dominated the region before 7.2 ka, and there was an optimal humid climate in 7.2?4.6 ka. Afterwards, the climate became obviously dry, accompanied with several cycles of relatively wet and dry, such as relatively wet intervals around 4.1?3.7 ka, 3.5?3.3 ka and 2.5 ka. In addition, six millennial-scale dry events were recorded, and these events were consistent with weaker Asian summer monsoonal intervals in low latitudes, declined palaeosol development and precipitation in middle latitudes, as well as increased winter monsoon and periodic ice-rafting events in high latitudes of the Northern Hemisphere, within limits of accuracy of existing dating ages. This possibly suggests a noteworthy synchronism between millennial-scale climatic changes in this region and on a global scale.

• A landscape management analysis framework and its preliminary application in Ejina Oasis, Northwest China
• YouHua Ran,Yan Zhao
• DOI:10.3724/SP.J.1226.2019.00239.
• 2019, 11 (3): 239–247 Abstract (24) HTML (0) PDF (7491 KB) (18)
• The implementation of integrated landscape management to support local and regional human well-being is crucial in arid regions, but its application to date is very limited. Although analytical frameworks have been established to maximize ecosystem services via trade-offs between different landscape configurations, consumption factors such as water resources are rarely and weakly considered in such frameworks. In this paper, an improved integrated landscape-management analysis framework, called the Consumption-integrated Landscape Management to Ecosystem Service (CLMES), is proposed. In this framework, consumption factors are integrated at the same level as ecosystem services. The improved analytical framework is then used to assess and optimize landscape design in the Ejina Oasis, an extremely arid region in western China. Three landscape conditions (past, current, and future) are evaluated, based on the CLMES. Our results indicate that the Heihe River water-allocation program effectively promoted ecosystem services in the Ejina Oasis from 2000 to 2011. However, the excessive expansion of cropland led to a slight decline in habitat quality. An optimized landscape configuration and policy suggestions are proposed, which may be beneficial to the improvement of total water-use efficiency, oasis stability, and resilience of the ecological-social system in the Ejina Oasis.

• Comparison of precipitation products to observations in Tibet during the rainy season
• Zhuo Ga,Za Dui,Duodian Luozhu,Jun Du
• DOI:10.3724/SP.J.1226.2018.00392
• 2018, 10 (5): 392–403 Abstract (25) HTML (5) PDF (7662 KB) (17)
• Precipitation is an important component of global water and energy transport and a major aspect of climate change. Due to the scarcity of meteorological observations, the precipitation climate over Tibet has been insufficiently documented. In this study, the distribution of precipitation during the rainy season over Tibet from 1980 to 2013 is described on monthly to annual time scales with meteorological observations. Furthermore, four precipitation products are compared to observations over Tibet. These datasets include products derived from the Asian Precipitation-Highly-Resolved Observational Data (APHRO), the Global Precipitation Climatology Centre (GPCC), the University of Delaware (UDel), and the China Meteorological Administration (CMA). The error, relative error, standard deviation, root-mean-square error, correlations and trends between these products for the same period are analyzed with in situ precipitation during the rainy season from May to September. The results indicate that these datasets can broadly capture the temporal and spatial precipitation distribution over Tibet. The precipitation gradually increases from northwest to southeast. The spatial precipitation in GPCC and CMA are similar and positively correlated to observations. Areas with the largest deviations are located in southwestern Tibet along the Himalayas. The APHRO product underestimates, while the UDel, GPCC, and CMA datasets overestimates precipitation on the basis of monthly and inter-annual variation. The biases in GPCC and CMA are smaller than those in APHRO and UDel with a mean relative error lower than 10% during the same periods. The linear trend of precipitation indicates that the increase in precipitation has accelerated extensively during the last 30 years in most regions of Tibet. The CMA generally achieves the best performance of these four precipitation products. Data uncertainty in Tibet might be caused by the low density of stations, complex topography between the grid points and stations, and the interpolation methods, which can also produce an obvious difference between the gridded data and observations.

• Increase in medium-size rainfall events will enhance the C-sequestration capacity of biological soil crusts
• CuiHua Huang,Fei Peng,Itaru Shibata,Jun Luo,Xian Xue,Kinya Akashi,Atsushi Tsunekawa,Tao Wang
• DOI:10.3724/SP.J.1226.2019.00081
• 2019, 11 (1): 81–92 Abstract (45) HTML (2) PDF (3973 KB) (17)
• Biological soil crusts (BSCs) play important roles in the carbon (C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs (the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount (SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae?lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen?moss crust on the windward. Even a small rainfall (1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and -emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5?10 mm rainfall events in the desert?oasis transitional zone.

• Glacier mapping based on Chinese high-resolution remote sensing GF-1 satellite and topographic data
• LiLi Yan,Jian Wang
• DOI:10.3724/SP.J.1226.2019.00218.
• 2019, 11 (3): 218–225 Abstract (22) HTML (1) PDF (8415 KB) (17)
• The precise glacier boundary is a fundamental requirement for glacier inventory, the assessment of climate change and water management in remote mountain areas. However, some glaciers in mountain areas are covered by debris. The high spatial resolution images bring opportunities in mapping debris-covered glaciers. To discuss the capability of Chinese GaoFen-1 satellite lacking the short wave infrared band and thermal infrared band in mapping glaciers, this study distinguished supraglacial terrain from surrounding debris by combining GaoFen-1 (GF-1) wide-field-view (WFV) images, the ratio of the thermal infrared imagery and morphometric parameters (DEM and slope) with 30 m resolution. The overall accuracy of 90.94% indicated that this method was effective for mapping supraglacial terrain in mountain areas. Comparing this result with the combination of GF-1 WFV and low-resolution morphometric parameters shows that a high-quality DEM and the thermal infrared band enhanced the accuracy of glacier mapping especially debris-covered ice in steep terrain. The user's and producer's accuracies of glacier area were also improved from 89.67% and 85.95% to 92.83% and 90.34%, respectively. GF data is recommended for mapping heavily debris-covered glaciers and will be combined with SAR data for future studies.

• Stem radial growth indicate the options of species, topography and stand management for artificial forests in the western Loess Plateau, China
• ShengChun Xiao,XiaoMei Peng,QuanYan Tian,Gong Zhu
• DOI:10.3724/SP.J.1226.2019.00226.
• 2019, 11 (3): 226–238 Abstract (22) HTML (0) PDF (4802 KB) (17)
• An understanding of the differences in artificial forest between tree species, slope aspects, and management options in arid environments is fundamentally important for efficient management of these artificial systems; however, few studies have quantified the spatial and temporal differences in stem radial growth of trees in the arid western Loess Plateau of China. Using dendrochronology, we assessed the growth of three woody species (the native shrub Reaumuria soongorica, the exotic shrub Tamarix ramosissima and tree Platycladus orientalis) by measuring the annual stem radial increment. We also describe the long-term growth trends and responses to climatic factors on slopes with different aspects during periods with and without irrigation. We found that precipitation during the main growing season was significantly positively correlated with ring growth for all three species and both slope aspects. In addition, supplemental water (e.g., irrigation, rainwater harvesting) greatly relieved drought stress and promoted radial growth. Our results suggest that as the main afforestation species in the Loess Plateau used for soil and water conservation, P. orientalis is more suitable than T. ramosissima under rain-fed conditions. However, a landscape that combined a tree (P. orientalis) with a shrub (R. soongorica) and grassland appears likely to represent the best means of ecological restoration in the arid western Loess Plateau.