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2019, 11 (2) Online: 01 April 2019
• 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, Vol.11 (2): 93–115 Abstract ( 27) HTML ( 5) PDF (9572 KB) ( 42 )
• 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.

• 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, Vol.11 (2): 116–125 Abstract ( 11) HTML ( 1) PDF (1590 KB) ( 23 )
• 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.

• 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, Vol.11 (2): 126–138 Abstract ( 8) HTML ( 0) PDF (10837 KB) ( 13 )
• 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.

• 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, Vol.11 (2): 139–149 Abstract ( 15) HTML ( 1) PDF (2660 KB) ( 23 )
• 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.

• 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, Vol.11 (2): 150–158 Abstract ( 21) HTML ( 2) PDF (34922 KB) ( 47 )
• 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.

• 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, Vol.11 (2): 159–172 Abstract ( 11) HTML ( 0) PDF (31417 KB) ( 19 )
• 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.

2019, Vol.11 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
2016, Vol.8 No.6 No.5 No.4 No.3 No.2 No.1
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 (151) HTML (19) PDF (4797 KB) (104)
• 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 (21) HTML (2) PDF (34922 KB) (47)
• 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 (25) HTML (7) PDF (10064 KB) (46)
• 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 (27) HTML (5) PDF (9572 KB) (42)
• 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.

• 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 (12) HTML (1) PDF (1442 KB) (35)
• 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.

• 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 (24) HTML (5) PDF (5751 KB) (30)
• 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.

• 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 (27) HTML (15) PDF (4839 KB) (27)
• 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 (24) HTML (10) PDF (480 KB) (26)
• 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.

• 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 (18) HTML (3) PDF (11448 KB) (24)
• 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.

• 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 (22) HTML (9) PDF (10529 KB) (24)
• 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.

• Intersection-pavement de-icing: comprehensive review and the state of the practice
• ZhaoHui Joey
• DOI:10.3724/SP.J.1226.2019.00001
• 2019, 11 (1): 1–12 Abstract (19) HTML (10) PDF (925 KB) (23)
• 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.

• 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 (11) HTML (1) PDF (1590 KB) (23)
• 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.

• 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 (15) HTML (1) PDF (2660 KB) (23)
• 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.

• 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 (13) HTML (2) PDF (662 KB) (22)
• 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.

• 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 (14) PDF (1727 KB) (21)
• 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.
• 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 (11) HTML (3) PDF (4973 KB) (20)
• 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.

• 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 (23) PDF (2396 KB) (20)
• 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 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 (11) HTML (0) PDF (31417 KB) (19)
• 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.

• 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 (19) HTML (1) PDF (4283 KB) (17)
• 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.

• 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 (21) HTML (4) PDF (30528 KB) (16)
• 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.

• Sociodemographic characteristics, cultural biases, and environmental attitudes: An empirical application of grid-group cultural theory in Northwestern China
• FangLei Zhong,AiJun Guo,XiaoJuan Yin,JinFeng Cui,Xiao Yang,YanQiong Zhang
• DOI:10.3724/SP.J.1226.2018.00436
• 2018, 10 (5): 436–446 Abstract (13) HTML (2) PDF (4595 KB) (15)
• Natural resource-management studies have become increasingly attentive to the influences of human factors. Among these, cultural biases shape people's responses to changes in natural resource systems. Several studies have applied grid-group cultural theory to assess the effects of multiple value biases among stakeholders on natural resource management. We developed and administered a questionnaire in the Heihe River Basin (n = 364) in northwestern China to investigate the appropriateness of applying this theory in the Chinese context of natural resource management. The results revealed various cultural biases among the respondents. In descending order of prevalence, these biases were hierarchism (46.98%), individualism (26.65%), egalitarianism (18.96%), and fatalism (2.78%), with the remaining respondents (4.67%) evidencing no obvious bias. Our empirical study revealed respondents' worldviews and the influence of sociodemographic characteristics on cultural biases, as theoretically posited. Among the variables examined, age had a positive and significant effect across all biases except individualism. The correlation of income to all cultural biases was consistently negative. Only education had a negative and significant effect across all biases. Women were found to adhere to egalitarianism, whereas men adhered to individualism and hierarchism. Thus, grid-group cultural theory was found to be appropriate in the Chinese context, with gender, age, education, and income evidently accounting for cultural biases. Relationships between environmental attitudes and cultural biases conformed with the hypothesis advanced by grid-group cultural theory. This finding may be of value in explaining individuals' environmental attitudes and facilitating the development and implementation of natural resource-management policies.

• 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 (9) HTML (5) PDF (7662 KB) (15)
• 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.

• 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 (10) HTML (0) PDF (10223 KB) (14)
• 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.

• 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 (25) HTML (5) PDF (2368 KB) (14)
• 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.

• 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 (8) HTML (0) PDF (10837 KB) (13)
• 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.

• Multifractal process of runoff fluctuation of the Kaidu River in Xinjiang, China
• ShuangQing Liu, ZuHan Liu, WeiGuo Wang, YuePing Lu, XiaoLiang Zhu, Bin Guo
• DOI:10.3724/SP.J.1226.2018.00232
• 2018, 10 (3): 232–239 Abstract (9) PDF (1619 KB) (12)
• Based on the hydrological data in the headwater region of the Kaidu River during 1972-2011, the multifractal process of runoff fluctuation was analyzed. Results indicated that, in the past 40 years, the overall runoff of the Kaidu River in Xinjiang has shown significant multifractal behavior. Its singular curve lnχq(ε)-ln(ε) verified a favorable scale invariance over the entire time scale. τ(q)-q proved that evolution of the runoff time series presented multifractal characteristics. Moreover, the multifractal spectrum f(α)-α curve was hooklike leftward which indicated that, compared to relatively large runoff events. And Δf<0 indicated that these relatively small events took the leading role; B<0 explained the Kaidu River's daily-runoff ascending tendency presented during 1972-2011. Besides that, the multifractal behavior of the Kaidu River's runoff variability over four decades was also analyzed. Generally speaking, by decades, their four corresponding spectrum variations were not noticeable. These Δα values showed larger runoff events occupied the leading position with some local values falling. During the 1970s to the 1990s, Δf<0 illustrated the probability of the daily runoff at the lowest point is always larger than that of the highest during three continuous decades. At the beginning of the 21st century, for Δf>0 the trend presented was contrary from the 1970s to the 1990s. B values suggested an overall trend of increases during 1972-2011. Until the 21st century, the runoff with a slightly descending tendency on the whole explained these relatively large runoff events taking the leading role for the Kaidu River; but sometimes, some small events also played the dominant role.
• Comparison of two classification methods to identify grain size fractions of aeolian sediment
• YanZai Wang,YongQiu Wu,MeiHui Pan,RuiJie Lu
• DOI:10.3724/SP.J.1226.2018.00413
• 2018, 10 (5): 413–420 Abstract (9) HTML (4) PDF (5099 KB) (12)
• Grain-size class-Std (GSCStd) and Grain-size class-dD (GSCdD) methods are simple statistical approaches for classifying bulk grain-size distributions (GSDs) into grain-size fractions. Although these two methods were developed based on similar statistical principles, the classification difference between these two methods has not been analyzed. In this study, GSCStd and GSCdD methods are conducted in thirteen grain-size data sequences to examine the applicability for identifying grain size fractions. Results show that, application of the GSCStd method is equivalent to that of the GSCdD method in identifying finer grain-size fractions, and the difference between the two methods mainly comes from the identification of coarse grain-size fractions. Thus, finer grain-size fractions are recommended for use in research of surface aeolian and paleo-aeolian sediments. In addition, our results do not completely agree with previous studies, coarser grain-size fractions in our case suggest that the GSCdD method may not be more applicable than the GSCStd method.

• 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 (17) HTML (3) PDF (544 KB) (12)
• 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.

• Biological improvement of saline alkali soil reference system: A review
• XueQin Wang,Xu Xing,FengJu Zhang,Kong Xin
• DOI:10.3724/SP.J.1226.2018.00000
• 2018, 10 (6): 516–521 Abstract (11) HTML (4) PDF (284 KB) (12)
• This work presents a reference system overview to improve the efficiency of biological improvement of saline-alkali soil developed during the last thirty years, ranging from connotation, general methods and species, soil desalination, soil structure, soil organic content, microbial flora, enzyme activity, yield and economic benefits. The reference system presented is divided into three main groups: suitable varieties, suitable cultivation measures, and a comprehensive evaluation system. There has been a lot of research on biological improvement of saline alkali soil, but these studies are very fragmented and lack a comprehensive standard system. Also, there is a lack of practical significance, particularly with regard to optimal species, densities and times of sowing for particular regions. On the other hand, the corresponding cultivation measure is very important. Therefore, a reference system plays an important role to the effect of biological improvement of saline alkali soil.

• Accumulation and geochemical evidence for the Little Ice Age episode in eastern Antarctica
• ChuanJin Li,JiaWen Ren,CunDe Xiao,MingHu Ding,AiHong Xie,ZhiHeng Du,XiangYu Ma,DaHe Qin
• DOI:10.3724/SP.J.1226.2019.00050
• 2019, 11 (1): 50–61 Abstract (7) HTML (4) PDF (2724 KB) (12)
• Data on accumulation and concentration of chemical compounds recorded in an essentially unexplored area (Dome Argus) of the Indian Ocean sector of eastern Antarctica during the past 2,680 years (680 B.C. to 1999 A.D.) are presented. During the first 1,700 years (680 B.C. to 1000 A.D.), the accumulation data shows a slightly decreasing trend, while chemical ions appear to be stable, representing a stable climatic condition. An intensive increasing trend of the accumulation occurred during the 12th to 14th century. The period from 15th to 19th century was characterized by a rapid reducing accumulation and concentrations of volatile compounds suffering post-depositional loss linked to sparse precipitation amount, which was temporally consistent with the Little Ice Age (LIA) episode. Comparison between observed accumulation rates with other eastern Antarctic ice cores show a consistent decreasing trend during LIA, while sea salt and dust-originated ions increased due to sea ice extent and intensified atmospheric transportation. Distribution of volcanic originated sulfate over the Antarctic continent show a significant change during the 15th century, coincident with the onset of the LIA. These results are important for the assessment of Antarctic continent mass balance and associated interpretation of the Dome A deep ice core records.

• Transcriptomic comparison to identify rapidly evolving genes in Braya humilis
• YuMing Wei,XiaoFei Ma,PengShan Zhao
• DOI:10.3724/SP.J.1226.2018.00428
• 2018, 10 (5): 428–435 Abstract (14) HTML (4) PDF (4412 KB) (11)
• The Brassicaceae species Braya humilis shows broad adaptation to different climatic zones and latitudes. However, the molecular adaptation mechanism of B. humilis is poorly understood. In China, B. humilis is mainly distributed on the Qinghai-Tibetan Plateau (QTP) and in the adjacent arid region. Previous transcriptome analysis of B. humilis has revealed that 39 salt and osmotic stress response genes are subjected to purifying selection during its speciation. To further explore the adaptation mechanism of B. humilis to an arid environment, OrthoMCL program was employed in this study and 6,268 pairs of orthologous gene pairs with high confidence were obtained betweenB. humilis and Arabidopsis thaliana. A comparative evolutionary analysis based on nonsynonymous to synonymous substitution ratio (Ka/Ks) was then conducted. There were 64 pairs exhibiting a Ka/Ks ratio more than 0.5 and among which, three instrumental candidate genes, T2_20487, T2_22576, and T2_13757, were identified with strong selection signatures (Ka/Ks >1). The corresponding A. thaliana orthologs are double-stranded RNA-binding domain protein, MADS-box family protein, and NADH-dehydrogenase subunit 6, which is encoded by mitochondria genome. This report not only demonstrates the adaptation contribution of fast evolving nuclear genes, but also highlights the potential adaptive value of mitochondria gene to the speciation and adaptation of B. humilis toward the extreme environment in an arid region.

• Analysis of water vapour flux between alpine wetlands underlying surface and atmosphere in the source region of the Yellow River
• Yan Xie,Jun Wen,Rong Liu,Xin Wang,DongYu Jia
• DOI:10.3724/SP.J.1226.2018.00305
• 2018, 10 (4): 305–316 Abstract (15) HTML (2) PDF (1908 KB) (10)
• An underlying wetland surface comprises soil, water and vegetation and is sensitive to local climate change. Analysis of the degree of coupling between wetlands and the atmosphere and a quantitative assessment of how environmental factors influence latent heat flux have considerable scientific significance. Using data from observational tests of the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS, from June 1 to August 31, 2014, this study analysed the time-varying characteristics and causes of the degree of coupling (Ω factor) between alpine wetlands underlying surface and the atmosphere and quantitatively calculated the influences of different environmental factors (solar radiation and vapour pressure deficit) on latent heat flux. The results were as follows: (1) Due to diurnal variations of solar radiation and wind speed, a trend developed where diurnal variations of the Ω factor were small in the morning and large in the evening. Due to the vegetation growing cycle, seasonal variations of the Ω factor present a reverse "U" trend. These trends are similar to the diurnal and seasonal variations of the absolute control exercised by solar radiation over latent heat flux. This conforms to the Omega Theory. (2) The values for average absolute atmospheric factor (surface factor or total) control exercised by solar radiation and water vapour pressure are 0.20 (0.02 or 0.22) and 0.005 (?0.07 or ?0.06) W/(m2·Pa), respectively. Generally speaking, solar radiation and water vapour pressure deficit exert opposite forces on latent heat flux. (3) At the underlying alpine wetland surface, solar radiation primarily influences latent heat flux through its direct effects (atmospheric factor controls). Water vapour pressure deficit primarily influences latent heat flux through its indirect effects (surface factor controls) on changing the surface resistance. (4) The average Ω factor in the underlying alpine wetland surface is high during the vegetation growing season, with a value of 0.38, and the degree of coupling between alpine wetland surface and atmosphere system is low. The actual measurements agree with the Omega Theory. The latent heat flux is mainly influenced by solar radiation.

• Spatiotemporal change of carbon storage in the Loess Plateau of northern Shaanxi, based on the InVEST Model
• ShaoYang Liu, NingKe Hu, Jin Zhang, ZhiChao Lv
• DOI:10.3724/SP.J.1226.2018.00240
• 2018, 10 (3): 240–250 Abstract (12) PDF (3607 KB) (10)
• In recent years, land use and land cover have under gone tremendous change on the Loess Plateau, leading to temporal and spatial variation over many ecological factors, such as carbon storage. Based on four series of land-use data from remote-sensing imaging, spatiotemporal changes of land-use types and volume changes were analyzed. Combined with carbon-stock-assessment modules of the InVEST (integrated valuation ecosystem services and tradeoffs) model, the carbon-storage change was estimated and analyzed at the subcounty and subbasin scales. The results show that (1) cultivated land and grassland area decreased, while woodland and urban land area increased in northern Shaanxi; (2) the average carbon storage in Huangling County and the Beiluo River Basin is the largest, while that of Yuyang County and the Xinshui River Basin is the minimum, and that of Wuqi County showed the greatest growth; (3) carbon storage in the study area showed a definite decrease in 2000, but in general has increased from 1995 to 2010; (4) carbon-storage figures of subbasins and counties are all restricted by the natural status and land-use landscape of the whole study area. From the results, it can be seen that the effect of ecological policies is remarkable. This study has important implications for the rational planning of land use, adjustment of the ecosystem carbon cycle, and related policies.
• A review on the ambit and prospects of C3 and C4 plants in Nigeria
• DOI:10.3724/SP.J.1226.2017.00587
• 2017, 9 (6): 587–598 Abstract (7) PDF (2416 KB) (10)
• Despite the enormous applications of photosynthesis in global carbon budget and food security, photosynthesis research has not been adequately explored as a research focus in Nigeria. Previous works on C3 and C4 plants in Nigeria were mainly on the use of anatomical characteristics to delimit plant species into their respective pathways, with no attention being paid to its applications. In this review, past and present knowledge gaps in this area of study are elucidated. Information used in this review were sourced from referred research articles and books in reputable journals. The results revealed that C3 and C4 plants are distributed among 21 genera and 11 families in Nigeria. In addition there is dearth of informatio such that only three genera have been classified based on diverse photosynthetic pathways with no information found on the physiological and biochemical characterization of these genera. Moreover, further research is also suggested for tackling new challenges in the area of food productivity and climate change.
• Tessellons, topography, and glaciations on the Qinghai-Tibet Plateau
• Stuart A. Harris, HuiJun Jin, RuiXia He, SiZhong Yang
• DOI:10.3724/SP.J.1226.2018.00187
• 2018, 10 (3): 187–206 Abstract (12)
• The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau (QTP). Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum (LGM), whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at >30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age (LIA) after 0.7 ka. Subsequently, mean annual air temperature has increased by 4℃.
• Freeze-thaw processes of active-layer soils in the Nanweng'he River National Natural Reserve in the Da Xing'anling Mountains, northern Northeast China
• RuiXia He, HuiJun Jin, XiaoLi Chang, YongPing Wang, LiZhong Wang
• DOI:10.3724/SP.J.1226.2018.00104
• 2018, 10 (2): 104–113 Abstract (7)
• The active-layer soils overlying the permafrost are the most thermodynamically active zone of rock or soil and play important roles in the earth-atmosphere energy system. The processes of thawing and freezing and their associated complex hydrothermal coupling can significantly affect variation in mean annual temperatures and the formation of ground ice in permafrost regions. Using soil-temperature and -moisture data obtained from the active layer between September 2011 and October 2014 in the permafrost region of the Nanweng'he River in the Da Xing'anling Mountains, the freeze-thaw characteristics of the permafrost were studied. Based on analysis of ground-temperature variation and hydrothermal transport characteristics, the thawing and freezing processes of the active layer were divided into three stages: (1) autumn-winter freezing, (2) winter freeze-up, and (3) spring-summer thawing. Variations in the soil temperature and moisture were analyzed during each stage of the freeze-thaw process, and the effects of the soil moisture and ground vegetation on the freeze-thaw are discussed in this paper. The study's results show that thawing in the active layer was unidirectional, while the ground freezing was bidirectional (upward from the bottom of the active layer and downward from the ground surface). During the annual freeze-thaw cycle, the migration of soil moisture had different characteristics at different stages. In general, during a freezing-thawing cycle, the soil-water molecules migrate downward, i.e., soil moisture transports from the entire active layer to the upper limit of the permafrost. In the meantime, freeze-thaw in the active layer can be significantly affected by the soil-moisture content and vegetation.
• Biodiversity, productivity, and temporal stability in a natural grassland ecosystem of China
• Bing Liu,WenZhi Zhao,YangYang Meng,Chan Liu
• DOI:10.3724/SP.J.1226.2018.00293
• 2018, 10 (4): 293–304 Abstract (10) HTML (2)
• Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richness and aboveground biomass, and simulated the competitive assemblages in a natural grassland ecosystem of China, aiming to test some assumptions and predictions about biodiversity–stability relationships. Our results show that aboveground productivity and temporal stability increased significantly with increasing species richness, and via a combination of overyielding, species asynchrony, and portfolio effects. Species interactions resulted in overyielding caused by trait-independent complementarity, and were not offset by a negative dominance effect and trait-dependent complementarity effect. Therefore, the mechanisms underlying the biodiversity effect shifted from the selection effect to the complementarity effect as diversity increased, and both effects were coexisted but the complementarity effect represent a mechanism that facilitates long term species coexistence in a natural grassland ecosystem of China.

• Fossil Taiwannia from the Lower Cretaceous Yixian Formation of western Liaoning, Northeast China and its phytogeography significance
• MingZhen Zhang,BaoXia Du,PeiHong Jin,BaiNian Sun
• DOI:10.3724/SP.J.1226.2018.00502
• 2018, 10 (6): 502–515 Abstract (5) HTML (1) PDF (784 KB) (9)
• Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures. Leaves are dimorphic, spirally and imbricately arranged. They are scale-like on the main and cone-bearing branchlets, and subulate to falcate-subulate on the juvenile or sterile shoots. The seed cones are singly elliptic, ovate or elongate-ovate and terminally borne on ultimate shoots, bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis, the bracts are broad-ovate, rhomboidal or hexagonal with entire margins. Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania. Furthermore, geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.

• 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 (151) HTML (19) PDF (4797 KB) (104)
• 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 (21) HTML (2) PDF (34922 KB) (47)
• 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 (25) HTML (7) PDF (10064 KB) (46)
• 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 (27) HTML (5) PDF (9572 KB) (42)
• 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.

• 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 (12) HTML (1) PDF (1442 KB) (35)
• 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.

• 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 (24) HTML (5) PDF (5751 KB) (30)
• 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.

• 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 (27) HTML (15) PDF (4839 KB) (27)
• 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 (24) HTML (10) PDF (480 KB) (26)
• 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.

• 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 (18) HTML (3) PDF (11448 KB) (24)
• 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.

• 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 (22) HTML (9) PDF (10529 KB) (24)
• 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.

• Intersection-pavement de-icing: comprehensive review and the state of the practice
• ZhaoHui Joey
• DOI:10.3724/SP.J.1226.2019.00001
• 2019, 11 (1): 1–12 Abstract (19) HTML (10) PDF (925 KB) (23)
• 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.

• 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 (11) HTML (1) PDF (1590 KB) (23)
• 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.

• 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 (15) HTML (1) PDF (2660 KB) (23)
• 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.

• 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 (13) HTML (2) PDF (662 KB) (22)
• 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.

• 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 (14) PDF (1727 KB) (21)
• 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.
• 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 (11) HTML (3) PDF (4973 KB) (20)
• 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.

• 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 (23) PDF (2396 KB) (20)
• 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 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 (11) HTML (0) PDF (31417 KB) (19)
• 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.

• 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 (19) HTML (1) PDF (4283 KB) (17)
• 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.

• 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 (21) HTML (4) PDF (30528 KB) (16)
• 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.

• Sociodemographic characteristics, cultural biases, and environmental attitudes: An empirical application of grid-group cultural theory in Northwestern China
• FangLei Zhong,AiJun Guo,XiaoJuan Yin,JinFeng Cui,Xiao Yang,YanQiong Zhang
• DOI:10.3724/SP.J.1226.2018.00436
• 2018, 10 (5): 436–446 Abstract (13) HTML (2) PDF (4595 KB) (15)
• Natural resource-management studies have become increasingly attentive to the influences of human factors. Among these, cultural biases shape people's responses to changes in natural resource systems. Several studies have applied grid-group cultural theory to assess the effects of multiple value biases among stakeholders on natural resource management. We developed and administered a questionnaire in the Heihe River Basin (n = 364) in northwestern China to investigate the appropriateness of applying this theory in the Chinese context of natural resource management. The results revealed various cultural biases among the respondents. In descending order of prevalence, these biases were hierarchism (46.98%), individualism (26.65%), egalitarianism (18.96%), and fatalism (2.78%), with the remaining respondents (4.67%) evidencing no obvious bias. Our empirical study revealed respondents' worldviews and the influence of sociodemographic characteristics on cultural biases, as theoretically posited. Among the variables examined, age had a positive and significant effect across all biases except individualism. The correlation of income to all cultural biases was consistently negative. Only education had a negative and significant effect across all biases. Women were found to adhere to egalitarianism, whereas men adhered to individualism and hierarchism. Thus, grid-group cultural theory was found to be appropriate in the Chinese context, with gender, age, education, and income evidently accounting for cultural biases. Relationships between environmental attitudes and cultural biases conformed with the hypothesis advanced by grid-group cultural theory. This finding may be of value in explaining individuals' environmental attitudes and facilitating the development and implementation of natural resource-management policies.

• 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 (9) HTML (5) PDF (7662 KB) (15)
• 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.

• 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 (10) HTML (0) PDF (10223 KB) (14)
• 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.

• 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 (25) HTML (5) PDF (2368 KB) (14)
• 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.

• 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 (8) HTML (0) PDF (10837 KB) (13)
• 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.

• Multifractal process of runoff fluctuation of the Kaidu River in Xinjiang, China
• ShuangQing Liu, ZuHan Liu, WeiGuo Wang, YuePing Lu, XiaoLiang Zhu, Bin Guo
• DOI:10.3724/SP.J.1226.2018.00232
• 2018, 10 (3): 232–239 Abstract (9) PDF (1619 KB) (12)
• Based on the hydrological data in the headwater region of the Kaidu River during 1972-2011, the multifractal process of runoff fluctuation was analyzed. Results indicated that, in the past 40 years, the overall runoff of the Kaidu River in Xinjiang has shown significant multifractal behavior. Its singular curve lnχq(ε)-ln(ε) verified a favorable scale invariance over the entire time scale. τ(q)-q proved that evolution of the runoff time series presented multifractal characteristics. Moreover, the multifractal spectrum f(α)-α curve was hooklike leftward which indicated that, compared to relatively large runoff events. And Δf<0 indicated that these relatively small events took the leading role; B<0 explained the Kaidu River's daily-runoff ascending tendency presented during 1972-2011. Besides that, the multifractal behavior of the Kaidu River's runoff variability over four decades was also analyzed. Generally speaking, by decades, their four corresponding spectrum variations were not noticeable. These Δα values showed larger runoff events occupied the leading position with some local values falling. During the 1970s to the 1990s, Δf<0 illustrated the probability of the daily runoff at the lowest point is always larger than that of the highest during three continuous decades. At the beginning of the 21st century, for Δf>0 the trend presented was contrary from the 1970s to the 1990s. B values suggested an overall trend of increases during 1972-2011. Until the 21st century, the runoff with a slightly descending tendency on the whole explained these relatively large runoff events taking the leading role for the Kaidu River; but sometimes, some small events also played the dominant role.
• Comparison of two classification methods to identify grain size fractions of aeolian sediment
• YanZai Wang,YongQiu Wu,MeiHui Pan,RuiJie Lu
• DOI:10.3724/SP.J.1226.2018.00413
• 2018, 10 (5): 413–420 Abstract (9) HTML (4) PDF (5099 KB) (12)
• Grain-size class-Std (GSCStd) and Grain-size class-dD (GSCdD) methods are simple statistical approaches for classifying bulk grain-size distributions (GSDs) into grain-size fractions. Although these two methods were developed based on similar statistical principles, the classification difference between these two methods has not been analyzed. In this study, GSCStd and GSCdD methods are conducted in thirteen grain-size data sequences to examine the applicability for identifying grain size fractions. Results show that, application of the GSCStd method is equivalent to that of the GSCdD method in identifying finer grain-size fractions, and the difference between the two methods mainly comes from the identification of coarse grain-size fractions. Thus, finer grain-size fractions are recommended for use in research of surface aeolian and paleo-aeolian sediments. In addition, our results do not completely agree with previous studies, coarser grain-size fractions in our case suggest that the GSCdD method may not be more applicable than the GSCStd method.

• 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 (17) HTML (3) PDF (544 KB) (12)
• 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.

• Biological improvement of saline alkali soil reference system: A review
• XueQin Wang,Xu Xing,FengJu Zhang,Kong Xin
• DOI:10.3724/SP.J.1226.2018.00000
• 2018, 10 (6): 516–521 Abstract (11) HTML (4) PDF (284 KB) (12)
• This work presents a reference system overview to improve the efficiency of biological improvement of saline-alkali soil developed during the last thirty years, ranging from connotation, general methods and species, soil desalination, soil structure, soil organic content, microbial flora, enzyme activity, yield and economic benefits. The reference system presented is divided into three main groups: suitable varieties, suitable cultivation measures, and a comprehensive evaluation system. There has been a lot of research on biological improvement of saline alkali soil, but these studies are very fragmented and lack a comprehensive standard system. Also, there is a lack of practical significance, particularly with regard to optimal species, densities and times of sowing for particular regions. On the other hand, the corresponding cultivation measure is very important. Therefore, a reference system plays an important role to the effect of biological improvement of saline alkali soil.

• Accumulation and geochemical evidence for the Little Ice Age episode in eastern Antarctica
• ChuanJin Li,JiaWen Ren,CunDe Xiao,MingHu Ding,AiHong Xie,ZhiHeng Du,XiangYu Ma,DaHe Qin
• DOI:10.3724/SP.J.1226.2019.00050
• 2019, 11 (1): 50–61 Abstract (7) HTML (4) PDF (2724 KB) (12)
• Data on accumulation and concentration of chemical compounds recorded in an essentially unexplored area (Dome Argus) of the Indian Ocean sector of eastern Antarctica during the past 2,680 years (680 B.C. to 1999 A.D.) are presented. During the first 1,700 years (680 B.C. to 1000 A.D.), the accumulation data shows a slightly decreasing trend, while chemical ions appear to be stable, representing a stable climatic condition. An intensive increasing trend of the accumulation occurred during the 12th to 14th century. The period from 15th to 19th century was characterized by a rapid reducing accumulation and concentrations of volatile compounds suffering post-depositional loss linked to sparse precipitation amount, which was temporally consistent with the Little Ice Age (LIA) episode. Comparison between observed accumulation rates with other eastern Antarctic ice cores show a consistent decreasing trend during LIA, while sea salt and dust-originated ions increased due to sea ice extent and intensified atmospheric transportation. Distribution of volcanic originated sulfate over the Antarctic continent show a significant change during the 15th century, coincident with the onset of the LIA. These results are important for the assessment of Antarctic continent mass balance and associated interpretation of the Dome A deep ice core records.

• Transcriptomic comparison to identify rapidly evolving genes in Braya humilis
• YuMing Wei,XiaoFei Ma,PengShan Zhao
• DOI:10.3724/SP.J.1226.2018.00428
• 2018, 10 (5): 428–435 Abstract (14) HTML (4) PDF (4412 KB) (11)
• The Brassicaceae species Braya humilis shows broad adaptation to different climatic zones and latitudes. However, the molecular adaptation mechanism of B. humilis is poorly understood. In China, B. humilis is mainly distributed on the Qinghai-Tibetan Plateau (QTP) and in the adjacent arid region. Previous transcriptome analysis of B. humilis has revealed that 39 salt and osmotic stress response genes are subjected to purifying selection during its speciation. To further explore the adaptation mechanism of B. humilis to an arid environment, OrthoMCL program was employed in this study and 6,268 pairs of orthologous gene pairs with high confidence were obtained betweenB. humilis and Arabidopsis thaliana. A comparative evolutionary analysis based on nonsynonymous to synonymous substitution ratio (Ka/Ks) was then conducted. There were 64 pairs exhibiting a Ka/Ks ratio more than 0.5 and among which, three instrumental candidate genes, T2_20487, T2_22576, and T2_13757, were identified with strong selection signatures (Ka/Ks >1). The corresponding A. thaliana orthologs are double-stranded RNA-binding domain protein, MADS-box family protein, and NADH-dehydrogenase subunit 6, which is encoded by mitochondria genome. This report not only demonstrates the adaptation contribution of fast evolving nuclear genes, but also highlights the potential adaptive value of mitochondria gene to the speciation and adaptation of B. humilis toward the extreme environment in an arid region.

• Analysis of water vapour flux between alpine wetlands underlying surface and atmosphere in the source region of the Yellow River
• Yan Xie,Jun Wen,Rong Liu,Xin Wang,DongYu Jia
• DOI:10.3724/SP.J.1226.2018.00305
• 2018, 10 (4): 305–316 Abstract (15) HTML (2) PDF (1908 KB) (10)
• An underlying wetland surface comprises soil, water and vegetation and is sensitive to local climate change. Analysis of the degree of coupling between wetlands and the atmosphere and a quantitative assessment of how environmental factors influence latent heat flux have considerable scientific significance. Using data from observational tests of the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS, from June 1 to August 31, 2014, this study analysed the time-varying characteristics and causes of the degree of coupling (Ω factor) between alpine wetlands underlying surface and the atmosphere and quantitatively calculated the influences of different environmental factors (solar radiation and vapour pressure deficit) on latent heat flux. The results were as follows: (1) Due to diurnal variations of solar radiation and wind speed, a trend developed where diurnal variations of the Ω factor were small in the morning and large in the evening. Due to the vegetation growing cycle, seasonal variations of the Ω factor present a reverse "U" trend. These trends are similar to the diurnal and seasonal variations of the absolute control exercised by solar radiation over latent heat flux. This conforms to the Omega Theory. (2) The values for average absolute atmospheric factor (surface factor or total) control exercised by solar radiation and water vapour pressure are 0.20 (0.02 or 0.22) and 0.005 (?0.07 or ?0.06) W/(m2·Pa), respectively. Generally speaking, solar radiation and water vapour pressure deficit exert opposite forces on latent heat flux. (3) At the underlying alpine wetland surface, solar radiation primarily influences latent heat flux through its direct effects (atmospheric factor controls). Water vapour pressure deficit primarily influences latent heat flux through its indirect effects (surface factor controls) on changing the surface resistance. (4) The average Ω factor in the underlying alpine wetland surface is high during the vegetation growing season, with a value of 0.38, and the degree of coupling between alpine wetland surface and atmosphere system is low. The actual measurements agree with the Omega Theory. The latent heat flux is mainly influenced by solar radiation.

• Spatiotemporal change of carbon storage in the Loess Plateau of northern Shaanxi, based on the InVEST Model
• ShaoYang Liu, NingKe Hu, Jin Zhang, ZhiChao Lv
• DOI:10.3724/SP.J.1226.2018.00240
• 2018, 10 (3): 240–250 Abstract (12) PDF (3607 KB) (10)
• In recent years, land use and land cover have under gone tremendous change on the Loess Plateau, leading to temporal and spatial variation over many ecological factors, such as carbon storage. Based on four series of land-use data from remote-sensing imaging, spatiotemporal changes of land-use types and volume changes were analyzed. Combined with carbon-stock-assessment modules of the InVEST (integrated valuation ecosystem services and tradeoffs) model, the carbon-storage change was estimated and analyzed at the subcounty and subbasin scales. The results show that (1) cultivated land and grassland area decreased, while woodland and urban land area increased in northern Shaanxi; (2) the average carbon storage in Huangling County and the Beiluo River Basin is the largest, while that of Yuyang County and the Xinshui River Basin is the minimum, and that of Wuqi County showed the greatest growth; (3) carbon storage in the study area showed a definite decrease in 2000, but in general has increased from 1995 to 2010; (4) carbon-storage figures of subbasins and counties are all restricted by the natural status and land-use landscape of the whole study area. From the results, it can be seen that the effect of ecological policies is remarkable. This study has important implications for the rational planning of land use, adjustment of the ecosystem carbon cycle, and related policies.
• A review on the ambit and prospects of C3 and C4 plants in Nigeria
• DOI:10.3724/SP.J.1226.2017.00587
• 2017, 9 (6): 587–598 Abstract (7) PDF (2416 KB) (10)
• Despite the enormous applications of photosynthesis in global carbon budget and food security, photosynthesis research has not been adequately explored as a research focus in Nigeria. Previous works on C3 and C4 plants in Nigeria were mainly on the use of anatomical characteristics to delimit plant species into their respective pathways, with no attention being paid to its applications. In this review, past and present knowledge gaps in this area of study are elucidated. Information used in this review were sourced from referred research articles and books in reputable journals. The results revealed that C3 and C4 plants are distributed among 21 genera and 11 families in Nigeria. In addition there is dearth of informatio such that only three genera have been classified based on diverse photosynthetic pathways with no information found on the physiological and biochemical characterization of these genera. Moreover, further research is also suggested for tackling new challenges in the area of food productivity and climate change.
• Tessellons, topography, and glaciations on the Qinghai-Tibet Plateau
• Stuart A. Harris, HuiJun Jin, RuiXia He, SiZhong Yang
• DOI:10.3724/SP.J.1226.2018.00187
• 2018, 10 (3): 187–206 Abstract (12)
• The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau (QTP). Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum (LGM), whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at >30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age (LIA) after 0.7 ka. Subsequently, mean annual air temperature has increased by 4℃.
• Freeze-thaw processes of active-layer soils in the Nanweng'he River National Natural Reserve in the Da Xing'anling Mountains, northern Northeast China
• RuiXia He, HuiJun Jin, XiaoLi Chang, YongPing Wang, LiZhong Wang
• DOI:10.3724/SP.J.1226.2018.00104
• 2018, 10 (2): 104–113 Abstract (7)
• The active-layer soils overlying the permafrost are the most thermodynamically active zone of rock or soil and play important roles in the earth-atmosphere energy system. The processes of thawing and freezing and their associated complex hydrothermal coupling can significantly affect variation in mean annual temperatures and the formation of ground ice in permafrost regions. Using soil-temperature and -moisture data obtained from the active layer between September 2011 and October 2014 in the permafrost region of the Nanweng'he River in the Da Xing'anling Mountains, the freeze-thaw characteristics of the permafrost were studied. Based on analysis of ground-temperature variation and hydrothermal transport characteristics, the thawing and freezing processes of the active layer were divided into three stages: (1) autumn-winter freezing, (2) winter freeze-up, and (3) spring-summer thawing. Variations in the soil temperature and moisture were analyzed during each stage of the freeze-thaw process, and the effects of the soil moisture and ground vegetation on the freeze-thaw are discussed in this paper. The study's results show that thawing in the active layer was unidirectional, while the ground freezing was bidirectional (upward from the bottom of the active layer and downward from the ground surface). During the annual freeze-thaw cycle, the migration of soil moisture had different characteristics at different stages. In general, during a freezing-thawing cycle, the soil-water molecules migrate downward, i.e., soil moisture transports from the entire active layer to the upper limit of the permafrost. In the meantime, freeze-thaw in the active layer can be significantly affected by the soil-moisture content and vegetation.
• Biodiversity, productivity, and temporal stability in a natural grassland ecosystem of China
• Bing Liu,WenZhi Zhao,YangYang Meng,Chan Liu
• DOI:10.3724/SP.J.1226.2018.00293
• 2018, 10 (4): 293–304 Abstract (10) HTML (2)
• Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richness and aboveground biomass, and simulated the competitive assemblages in a natural grassland ecosystem of China, aiming to test some assumptions and predictions about biodiversity–stability relationships. Our results show that aboveground productivity and temporal stability increased significantly with increasing species richness, and via a combination of overyielding, species asynchrony, and portfolio effects. Species interactions resulted in overyielding caused by trait-independent complementarity, and were not offset by a negative dominance effect and trait-dependent complementarity effect. Therefore, the mechanisms underlying the biodiversity effect shifted from the selection effect to the complementarity effect as diversity increased, and both effects were coexisted but the complementarity effect represent a mechanism that facilitates long term species coexistence in a natural grassland ecosystem of China.

• Fossil Taiwannia from the Lower Cretaceous Yixian Formation of western Liaoning, Northeast China and its phytogeography significance
• MingZhen Zhang,BaoXia Du,PeiHong Jin,BaiNian Sun
• DOI:10.3724/SP.J.1226.2018.00502
• 2018, 10 (6): 502–515 Abstract (5) HTML (1) PDF (784 KB) (9)
• Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures. Leaves are dimorphic, spirally and imbricately arranged. They are scale-like on the main and cone-bearing branchlets, and subulate to falcate-subulate on the juvenile or sterile shoots. The seed cones are singly elliptic, ovate or elongate-ovate and terminally borne on ultimate shoots, bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis, the bracts are broad-ovate, rhomboidal or hexagonal with entire margins. Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania. Furthermore, geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.