2020, 12 (3) Online: 30 June 2020 Previous issue
  • A modified numerical model for moisture-salt transport in unsaturated sandy soil under evaporation
  • Wei Wen,YuanMing Lai,ZheMin You
  • DOI: 10.3724/SP.J.1226.2020.00125
  • 2020, Vol.12 (3): 125–133 Abstract ( 37) HTML ( 7) PDF (4133 KB) ( 32 )
  • Soil salinization, caused by salt migration and accumulation underneath the soil surface, will corrode structures. To analyze the moisture-salt migration and salt precipitation in soil under evaporation conditions, a mathematical model consisting of a series of theoretical equations is briefly presented. The filling effect of precipitated salts on tortuosity factor and evaporation rate are taken into account in relevant equations. Besides, a transition equation to link the solute transport equation before and after salt precipitation is proposed. Meanwhile, a new relative humidity equation deduced from Pitzer ions model is used to modify the vapor transport flux equation. The results show that the calculated values are in good agreement with the published experimental data, especially for the simulation of volume water content and evaporation rate of Toyoura sand, which confirm the reliability and applicability of the proposed model.

  • Numerical simulations on cutting of frozen soil using HJC Model
  • WenQiang Zhang,YongHong Niu
  • DOI: 10.3724/SP.J.1226.2020.00134
  • 2020, Vol.12 (3): 134–143 Abstract ( 33) HTML ( 3) PDF (4939 KB) ( 22 )
  • Numerical simulation is known as an effective method for mechanical properties during frozen soil excavation. In order to reveal the development of cutting force, effective stress and cutting fragments in frozen silt during the cutting process, we introduce an explicit finite element program LS-DYNA to establish a two-dimensional numerical model of the frozen soil cut. We also use the Holmquist-Johnson-Cook (HJC) damage constitutive model for simulating the variation of soil mechanical properties according to the strong dependence between the cutting tool and frozen silt during the process with different cutting depths, angles and velocities. Meanwhile, a series of experimental results are acquired of frozen silt cutting to prove the application of the HJC model during simulation of cutting force variations. The result shows that the cutting force and fragment size are strongly influenced by cutting depths and cutting velocities increased, and the maximum effective stress at points where the tool contacts frozen soil during the cutting process. In addition, when the cutting angle is 52°, the cutting force is the smallest, and the cutting angle is optimum. Thus, the prediction of frozen soil mechanical properties on the cutting process by this model is conducive to selecting machinery equipment in the field.

  • Mapping the dynamic degree of aeolian desertification in the Shiyang River Basin from 1975 to 2010
  • Jie Liao,Tao Wang,ShaoXiu Ma,Jian Guo
  • DOI: 10.3724/SP.J.1226.2020.00144
  • 2020, Vol.12 (3): 144–153 Abstract ( 27) HTML ( 3) PDF (5783 KB) ( 36 )
  • The Shiyang River Basin is an area of China that is severly affected by aeolian desertification. Thus, we established an aeolian desertified land classification system for visual interpretation, which classified the Aeolian Desertified Land (ADL) into Slight (SL), Moderate (M), Severe (S) and Extremely Severe (ES) according to the severity. Imagery of Landsat series (acquired in 1975, 1990, 2000 and 2010) were employed to monitor the status, trend and spatial pattern of aeolian desertification, especially to map the overall spatial pattern of ADL dynamics by proposing a new Dynamic Index (DI) in the Shiyang River Basin from 1975 to 2010. The results show a generally decreasing trend from 1975 to 2010. However, the ES ADL kept increasing throughout the whole study period. Moreover, the area of ADLs with different severity increased with increasing severity, this S and ES ADLs dominated characteristics of aeolian desertification was contrary to those sandy lands in eastern China where was dominated by SL and M ADLs. Among the three sub-periods of 1975-1990, 1990-2000 and 2000-2010, the first two were the restoration stage, while the last one was the expansion stage of aeolian desertification. Moreover, all these new ADLs occurred in Minqin County during 2000-2010, indicating a detrimental increase of aeolian desertification in Minqin, and the concentration of ADLs toward the lower reaches of the Shiyang River Basin. The DI works well to identify areas with desertification changes no matter the sub-periods. Moreover, DI results disclosed a stable status of aeolian desertification, and the DI decreased with increasing ADL severity. These results indicate that it will be difficult to control the expansion of aeolian desertification in Minqin County over an extended period of time. Thus, we suggest effective and long-lasting aeolian desertification control programs in the Shiyang River Basin, especially in Minqin, and SL and M ADLs should have priority in facilitating a quick reversal of aeolian desertification.

  • Quantitatively estimate the components of natural runoff and identify the impacting factors in asnow-fed river basin of China
  • Jia Qin,JinKui Wu,TianDing Han,QiuDong Zhao
  • DOI: 10.3724/SP.J.1226.2020.00154
  • 2020, Vol.12 (3): 154–164 Abstract ( 18) HTML ( 0) PDF (6844 KB) ( 10 )
  • Snowmelt water is an essential runoff source of some alpine rivers in China. This study selected the Upper Burqin River (UBR), a typical snow-fed river, to quantitatively assess the runoff contributions of different components, as well as the causes of runoff variations under the background of cryosphere change and global warming. Based on the spatial-temporal distributions of snow and glaciers during a year, as well as the altitudinal variations of 0 °C isotherm, the high flow hydrographs in UBR was separated into two parts: seasonal snowmelt flood of lower altitudes (<3,000 m) and glacier-snow melt flow in high altitudes (3,000-4,296 m). The daily baseflow hydrograph of UBR was separated by the digital filtering technique. It is concluded that the contributions of snowmelt flow, glacier melt flow, and baseflow (includes rainfall runoff component) to total annual flow volumes are 27.2% (±2.7%), 8.5% (±1.7%), and 64.3% (±3.0%), respectively. The speed of air temperature rise in spring may be the controlling factor for monthly snowmelt flow distributions in the snow-fed river. The volume of snowmelt was determined by spring precipitation (SP) and previous winter's precipitation (PWP). The PWP changes can explain 43.7% of snowmelt changes during 1981-2010 in UBR, while snowmelt change in 1957-1980 is more impacted by SP. The determining factor of snowmelt variation was changed from SP to PAP during the recent decades. Precipitation in current year, excluding previous year's rainfall and snowfall, can only explain 32%-70% of the variability in total runoff.

  • A meta-analysis of the impacts of forest logging on soil CO2 efflux
  • LongFei Chen,YangZhou Xiang,ZhiBin He,Jun Du,PengFei Lin,Xi Zhu
  • DOI: 10.3724/SP.J.1226.2020.00165
  • 2020, Vol.12 (3): 165–179 Abstract ( 18) HTML ( 2) PDF (4619 KB) ( 12 )
  • Soil CO2 efflux, the second largest flux in a forest carbon budget, plays an important role in global carbon cycling. Forest logging is expected to have large effects on soil CO2 efflux and carbon sequestration in forest ecosystems. However, a comprehensive understanding of soil CO2 efflux dynamics in response to forest logging remains elusive due to large variability in results obtained across individual studies. Here, we used a meta-analysis approach to synthesize the results of 77 individual field studies to determine the impacts of forest logging on soil CO2 efflux. Our results reveal that forest logging significantly stimulated soil CO2 efflux of the growing season by 5.02%. However, averaged across all studies, non-significant effect was detected following forest logging. The large variation among forest logging impacts was best explained by forest type, logging type, and time since logging. Soil CO2 efflux in coniferous forests exhibited a significant increase (4.38%) due to forest logging, while mixed and hardwood forests showed no significant change. Logging type also had a significant effect on soil CO2 efflux, with thinning increasing soil CO2 efflux by 12.05%, while clear-cutting decreasing soil CO2 efflux by 8.63%. The time since logging also had variable effects, with higher soil CO2 efflux for 2 years after logging, and lower for 3-6 years after logging; when exceeded 6 years, soil CO2 efflux increased. As significantly negative impacts of forest logging were detected on fine root biomass, the general positive effects on soil CO2 efflux can be explained by the accelerated decomposition of organic matter as a result of elevated soil temperature and organic substrate quality. Our results demonstrate that forest logging had potentially negative effects on carbon sequestration in forest ecosystems.

  • Fast genetic mapping in barley: case studies of cuticle mutants using RNA-sequencing
  • XiaoFeng Li,Chao Li,Qin Zhou,GuoXiong Chen,PengShan Zhao
  • DOI: 10.3724/SP.J.1226.2020.00180
  • 2020, Vol.12 (3): 180–188 Abstract ( 19) HTML ( 0) PDF (2688 KB) ( 37 )
  • Barley (Hordeum vulgare L.) is one of the earliest domesticated crop species and ranked as the fourth largest cereal production worldwide. Forward genetic studies in barley have greatly advanced plant genetics during the last century; however, most genes are identified by the conventional mapping method. Array genotyping and exome-capture sequencing have also been successfully used to target the causal mutation in barley populations, but these techniques are not widely adopted because of associated costs and partly due to the huge genome size of barley. This review summarizes three mapping cases of barley cuticle mutants in our laboratory with the help of RNA-sequencing. The causal mutations have been successfully identified for two of them and the target genes are located in the pericentromeric regions. Detailed information on the mapping-by-sequencing, mapping-and-sequencing, and RNA-sequencing assisted linkage mapping are presented and some limitations and challenges on the mapping assisted by RNA sequencing are also discussed. The alternative and elegant methods presented in this review may greatly accelerate forward genetics of barley mapping, especially for laboratories without large funding.

2020, Vol.12 No.2 No.1
2019, Vol.11 No.6 No.5 No.4 No.3 No.2 No.1
2018, Vol.10 No.6 No.5 No.4 No.3 No.2 No.1
2017, Vol.9 No.6 No.5 No.4 No.3 No.2 No.1
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
  • Seed germination and seedling growth of Pycnanthus angolensis (Welw.) Warb., African false nutmeg
  • Sakpere A.M.A.
  • DOI:10.3724/SP.J.1226.2019.00350.
  • 2019, 11 (5): 350–359 Abstract (107) HTML (150) PDF (2153 KB) (221)
  • This study investigated the germination behavior and seedling growth of Pycnanthus angolensis seeds. The germination study was carried out in the laboratory and included pretreatment studies and observation of the seed-germination process. For each treatment, three replications of 20 seeds were sown in a transparent plastic germination box (12cm × 22cm × 5cm) lined with moistened filter paper at room temperature. To monitor seedling growth, seedlings were transplanted into pots filled with topsoil and laid out in a completely randomized design. Ten seedlings replicated thrice were measured monthly; and the shoot height, leaf area, and root length, as well as the fresh and dry weights of the seedlings, were recorded. Results showed that mechanically scarified seeds exhibited the significantly highest germination percent (83.33%, P <0.005), followed by control seeds (70.83%), whereas seeds treated with 98% sulphuric acid (H2SO4) displayed the lowest germination percent (1.67). The endospermous seeds exhibited cryptogeal germination, while seeds stored for a month (with or without arils) failed to germinate. During seed germination, radicle protrusion continued with a pseudo-opening of the root, through which the brownish cotyledonary petiole was emitted, thus releasing the plumule at the posterior position. Moreover, P. angolensis exhibited a slow growth rate, attaining a shoot height of 73 cm within a year. The highest positive change in leaf number and area was recorded in the fourth month, a period during which the least change in shoot height occurred. The study concluded that mechanical scarification of the seeds ensured significant and faster germination than chemical scarification or no treatment at all. Additionally, P. angolensis displayed a cryptogeal germination, with the seedling growth of the tree species observed to be slow.

  • Research on pile performance and state-of-the-art practice in cold regions
  • JianKun Liu, TengFei Wang, Zhi Wen
  • DOI:10.3724/SP.J.1226.2018.00001
  • 2018, 10 (1): 1–11 Abstract (181) PDF (3430 KB) (209)
  • A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows: (1) creep tests and bearing capacity, (2) frost-jacking hazards, (3) laterally loaded piles, (4) dynamic responses, (5) refreezing due to concrete-hydration heat, and (6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.
  • 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 (272) HTML (192) PDF (4797 KB) (179)
  • 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.

  • An evaluation of soil moisture from AMSR-E over source area of the Yellow River, China
  • TangTang Zhang,Mekonnen Gebremichael,Akash Koppa,XianHong Meng,Qun Du,Jun Wen
  • DOI:10.3724/SP.J.1226.2019.00461.
  • 2019, 11 (6): 461–469 Abstract (145) HTML (136) PDF (2806 KB) (147)
  • In this study, in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture products from NASA (National Aeronautics and Space Administration), JAXA (Japanese Aerospace Exploration Agency) and VUA (Vrije University Amsterdam and NASA) over Maqu County, Source Area of the Yellow River (SAYR), China. Results show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area, with a minimum RMSE (root mean square error) of 0.08 (0.10) m3/m3 and smallest absolute error of 0.07 (0.08) m3/m3 at the grassland area with ascending (descending) data. Therefore, the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR. The VUA soil moisture product shows that soil moisture presents a declining trend from east south (0.42 m3/m3) to west north (0.23 m3/m3), with good agreement with a general precipitation distribution. The center of SAYR presents extreme wetness (0.60 m3/m3) during the whole study period, especially in July, while the head of SAYR presents a high level soil moisture (0.23 m3/m3) in July, August and September.

  • Soil freezing process and different expressions for the soil-freezing characteristic curve
  • JunPing Ren, Sai K. Vanapalli, Zhong Han
  • DOI:10.3724/SP.J.1226.2017.00221
  • 2017, 9 (3): 221–228 Abstract (148) PDF (4411 KB) (132)
  • The soil-freezing characteristic curve (SFCC), which represents the relationship between unfrozen water content and sub-freezing temperature (or suction at ice-water interface) in a freezing soil, can be used for understanding the transportation of heat, water, and solute in frozen soils. In this paper, the soil freezing process and the similarity between the SFCC of saturated frozen soil and soil-water characteristic curve (SWCC) of unfrozen unsaturated soil are reviewed. Based on similar characteristics between SWCC and SFCC, a conceptual SFCC is drawn for illustrating the main features of soil freezing and thawing processes. Various SFCC expressions from the literature are summarized. Four widely used expressions (i.e., power relationship, exponential relationship, van Genuchten 1980 equation and Fredlund and Xing 1994 equation) are evaluated using published experimental data on four different soils (i.e., sandy loam, silt, clay, and saline silt). Results show that the exponential relationship and van Genuchten (1980) equation are more suitable for sandy soils. The simple power relationship can be used to reasonably best-fit the SFCC for soils with different particle sizes; however, it exhibits limitations when fitting the saline silt data. The Fredlund and Xing (1994) equation is suitable for fitting the SFCCs for all soils studied in this paper.
  • Qualitative and quantitative phytochemical analysis of selected mosses with different alcoholic solvents
  • Kehinde O. Olasoji,Amos M. Makinde,Bolajoko A. Akinpelu,Musibau O. Isa
  • DOI:10.3724/SP.J.1226.2019.00382.
  • 2019, 11 (5): 382–388 Abstract (67) HTML (8) PDF (670 KB) (132)
  • This study was conducted to investigate the qualitative and quantitative phytochemical content of the crude extracts of Archidium ohioense, Pelekium gratum, and Hyophila involuta with different alcoholic solvents (ethanol, methanol, Seaman's Schnapps, fresh oil-palm wine, and fresh Raffia-palm wine). The mosses were collected from their natural populations on the central campus of the Obafemi Awolowo University, Ile-Ife, Nigeria. The yield of the extracts was weighed for all the solvents, and the qualitative and quantitative evaluations of the extracts were carried out using standard methods. The results of phytochemical analysis of the crude extracts from the mosses showed the presence of saponins, cardiac glycosides, triterpenes, alkaloids, flavonoids, and steroids. The quantitative phytochemical analysis of the crude extracts showed that ethanolic extracts of Hyophila involuta had the highest flavonoid content (288.37±0.10 mg RE/g), and Raffia-palm-wine extracts of Hyophila involuta had the highest saponin content (224.70±0.02 mg/g), while the methanolic extract of Archidium ohioense had the highest cardiac glycosides content (63.71±0.14 mg/g), and the Raffia-palm wine extract of Hyophila involuta had the highest alkaloids content (102.50±0.12 mg/g). Raffia- and oil-palm wines were observed to be the most effective solvents for all the mosses studied, followed by Seaman's Schnapp, while methanol and ethanol were less effective. The study concluded that the extracts of the mosses studied contain pharmacologically active constituents that can be used for therapeutic purposes.

  • Comparative study of probable maximum precipitation and isohyetal maps for mountainous regions, Pakistan
  • Muhammad Waseem Boota, Ghulam Nabi, Tanveer Abbas, HuiJun Jin, Ayesha Yousaf, Muhammad Azeem Boota
  • DOI:10.3724/SP.J.1226.2018.00055
  • 2018, 10 (1): 55–68 Abstract (74) PDF (4789 KB) (126)
  • Probable maximum precipitation (PMP) is widely used by hydrologists for appraisal of probable maximum flood (PMF) used for soil and water conservation structures, and design of dam spillways. A number of methods such as empirical, statistical and dynamic are used to estimate PMP, the most favored being statistical and hydro-meteorological. In this paper, PMP estimation in mountainous regions of Pakistan is studied using statistical as well as physically based hydro-meteorological approaches. Daily precipitation, dew point, wind speed and temperature data is processed to estimate PMP for a one-day duration. Maximum precipitation for different return periods is estimated by using statistical approaches such as Gumble and Log-Pearson type-III (LP-III) distribution. Goodness of fit (GOF) test, chi-square test, correlation coefficient and coefficient of determination were applied to Gumble and LP-III distributions. Results reveal that among statistical approaches, Gumble distribution performed the best result compared to LP-III distribution. Isohyetal maps of the study area at different return periods are produced by using the GIS tool, and PMP in mountainous regions varies from 150 to 320 mm at an average value of 230.83 mm. The ratio of PMP for one-day duration to highest observed rainfall (HOR) varied from 1.08 to 1.29 with an average value of 1.18. An appropriate frequency factor (Km) is very important which is a function of mean for observed precipitation and PMP for 1-day duration, and Km values varies from 2.54 to 4.68. The coefficient of variability (Cv) varies from minimum value of 28% to maximum value of 43.35%. It was concluded that the statistical approach gives higher results compared to moisture maximization (MM) approach. In the hydro-meteorological approach, moisture maximization (MM) and wind moisture maximization (WMM) techniques were applied and it was concluded that wind moisture maximization approach gives higher results of PMP as compared to moisture maximization approach as well as for Hershfield technique. Therefore, it is suggested that MM approach is the most favored in the study area for PMP estimation, which leads to acceptable results, compared to WMM and statistical approaches.
  • Relationship between ponding and topographic factors along the China-Russia Crude Oil Pipeline in permafrost regions
  • MingTang Chai,YanHu Mu,GuoYu Li,Wei Ma,Fei Wang
  • DOI:10.3724/SP.J.1226.2019.00419.
  • 2019, 11 (6): 419–427 Abstract (111) HTML (15) PDF (4231 KB) (122)
  • The original landform along the China-Russia Crude Oil Pipeline (CRCOP, line 2) was disturbed during installation of pavement for the pipeline. Forest and vegetation coverage is dense, and runoff develops along the pipe. Since the operation of the CRCOP (line 2) began in 2018, ponding has appeared on both sides of the pipeline. If there is no drainage, ponding can hardly dissipate, due to the low permeability of the permafrost layer. With the supply of surface flow and the transportation of oil at positive temperatures, ponding promotes an increase in temperature and changes the boundary thermal conditions of the pipeline. Meanwhile, when the ponding freezes and thaws, frost heave threatens operational safety of the pipeline. Furthermore, the ponding can affect the thermal condition of line 1. In this paper, the distribution of ponding along the CRCOP was obtained by field investigation. The type and cause of ponding were summarized, and the catchment and stream order were extracted by the Digital Elevation Model (DEM). According to the statistical results in attributes for topographic factors, it is known that ponding along the pipeline is relative to elevation, slope, aspect, and the Topographic Wetness Index (TWI). Water easily accumulates at altitudes of 300-450 m, slopes within 3°-5°, aspect in the northeast or south, TWI within 13-16, flow direction in north-east-south, and flow length within 90-150 km. This paper proposes a theoretical basis for the cause and characteristics of ponding along the pipeline.

  • Cutting of Phragmites australis as a lake restoration technique: Productivity calculation and nutrient removal in Wuliangsuhai Lake, northern China
  • Jan Felix Köbbing, Niels Thevs, Stefan Zerbe
  • DOI:10.3724/SP.J.1226.2016.00400
  • 2016, 8 (5): 400–410 Abstract (68) PDF (2545 KB) (118)
  • Reed is one of the most frequent and dominant species in wetlands all over the world, with common reed (Phragmites australis (Cav.) Trin. ex Steud.) as the most widely distributed species. In many wetlands, P. australis plays a highly ambivalent role. On the one hand, in many wetlands it purifies wastewater, provides habitat for numerous species, and is a potentially valuable raw material, while on the other hand it is an invasive species which expands aggressively, prevents fishing, blocks ditches and waterways, and builds monospecies stands. This paper uses the eutrophic reed-swamp of Wuliangsuhai Lake in Inner Mongolia, northern China, as a case to present the multiple benefits of regular reed cutting. The reed area and aboveground biomass production are calculated based on field data. Combined with data about water and reed nutrient content, the impact of reed cutting on the lake nutrient budget (N and P) is investigated. Currently, at this lake around 100,000 tons of reed are harvested in winter annually, removing 16% and 8% of the total nitrogen and phosphorus influx, respectively. Harvesting all available winter reed could increase the nutrient removal rates to 48% and 24%, respectively. We also consider the effects of summer harvesting, in which reed biomass removal could overcompensate for the nutrient influx but could potentially reduce reed regrowth.
  • A review on the ambit and prospects of C3 and C4 plants in Nigeria
  • Abdulwakeel Ayokun-nun Ajao, Oludare Oladipo Agboola, Sefiu Adekilekun Saheed
  • DOI:10.3724/SP.J.1226.2017.00587
  • 2017, 9 (6): 587–598 Abstract (50) PDF (2416 KB) (117)
  • 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.
  • 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 (74) HTML (6) PDF (4973 KB) (116)
  • 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.

  • Influence of proximity to the Qinghai-Tibet highway and railway on variations of soil heavy metal concentrations and bacterial community diversity on the Tibetan Plateau
  • Xia Zhao,JunFeng Wang,Yun Wang,Xiang Lu,ShaoFang Liu,YuBao Zhang,ZhiHong Guo,ZhongKui Xie,RuoYu Wang
  • DOI:10.3724/SP.J.1226.2019.00407.
  • 2019, 11 (6): 407–418 Abstract (96) HTML (14) PDF (4670 KB) (116)
  • An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway (QTH) revealed that the accumulation of heavy metals (over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway (QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria. The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR (MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR (MA/WA sampling sites). The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.

  • Measurement for coordinated development of "four modernizations" and its efficiency of prefecture level cities or above in China
  • JingHu Pan, YanXing Hu
  • DOI:10.3724/SP.J.1226.2016.00163
  • 2016, 8 (2): 163–176 Abstract (56) PDF (697 KB) (113)
  • The efficient and coordinated development of industrialization,urbanization,informatization and agricultural modernization(so called "Sihua Tongbu" in China,and hereinafter referred to as "four modernizations") is not only a practical need but also an important strategic direction of integrating urban-rural development and regional development in recent China.This paper evaluated the comprehensive,coupling and coordinated developmental indices of "four modernizations" of China's 343 prefecture-level administrative units,and calculated their efficiency of "four modernizations" in 2001 and 2011.The efficiency evaluation index system was established.The efficiencies and their changing trend during the period 2001-2011 were investigated using the data envelopment analysis(DEA) model.Spatial-temporal pattern of the efficiency of China's prefecture-level units was explored by using exploratory spatial data analysis(ESDA).Finally,the main influencing factors were revealed with the aid of geographically weighted regression(GWR) model.Results indicate that the comprehensive,coupling and coordinated developmental indices and efficiency of "four modernizations" of China's prefecture-level administrative units have obvious spatial differences and show diverse regional patterns.Overall,the efficiency is relatively low,and only few units with small urban populations and economic scale are in DEA efficiencies.The efficiency changing trends were decreasing during 2001-2011,with a transfer of high efficiency areas from inland to eastern coastal areas.The difference between urban and rural per capita investment in fixed assets boasts the greatest influence on the efficiency.
  • Analysis of structural characteristics and spatial distribution of the national intangible cultural heritage in China and its policy implications
  • BaiCui Xu,JingHu Pan
  • DOI:10.3724/SP.J.1226.2019.00389.
  • 2019, 11 (5): 389–406 Abstract (78) HTML (10) PDF (4506 KB) (107)
  • Based on an investigation of four published batches listing 3,140 national intangible cultural heritage (ICH) projects in China and using GIS and some quantitative analysis methods, the spatial structure was investigated and the characteristics and distribution discussed. The distribution of ICHs in China is agglomerative and spatially dependent. From the view of ICH type, each type is distributed in different places, for different reasons, with history being the most important one we found. Nationwide, high-density cores are located in the Beijing-Tianjin-Hebei region and the Yangtze River Delta region. High densities of ICH are concentrated in flat, water-rich regions where broad-leaved forests dominate plains and low mountain areas—areas that have fertile soil, pleasant weather, a long history of culture, ethnic agglomeration, and development. This paper suggests that development of the ICH should be based on discovering unknown items, to break the existing pattern of strong cohesion and high density, and to seek a balanced development of the whole.

  • Estimating interaction between surface water and groundwater in a permafrost region of the northern Tibetan Plateau using heat tracing method
  • TanGuang Gao,Jie Liu,TingJun Zhang,ShiChang Kang,ChuanKun Liu,ShuFa Wang,Mika Sillanpää,YuLan Zhang
  • DOI:10.3724/SP.J.1226.2020.00071.
  • 2020, 12 (2): 71–82 Abstract (94) HTML (7) PDF (4245 KB) (107)
  • Understanding the interaction between groundwater and surface water in permafrost regions is essential to study flood frequencies and river water quality, especially in the high latitude/altitude basins. The application of heat tracing method, based on oscillating streambed temperature signals, is a promising geophysical method for identifying and quantifying the interaction between groundwater and surface water. Analytical analysis based on a one-dimensional convective-conductive heat transport equation combined with the fiber-optic distributed temperature sensing method was applied on a streambed of a mountainous permafrost region in the Yeniugou Basin, located in the upper Heihe River on the northern Tibetan Plateau. The results indicated that low connectivity existed between the stream and groundwater in permafrost regions. The interaction between surface water and groundwater increased with the thawing of the active layer. This study demonstrates that the heat tracing method can be applied to study surface water-groundwater interaction over temporal and spatial scales in permafrost regions.

  • Cracking in an expansive soil under freeze–thaw cycles
  • Yang Lu, SiHong Liu
  • DOI:10.3724/SP.J.1226.2017.00392
  • 2017, 9 (4): 392–397 Abstract (120) PDF (2977 KB) (106)
  • Expansive soils located in cold regions can easily endure the action of frost heaving and cyclic freezing–thawing. Cracking can also occur in expansive clayey soils under freeze–thaw cycles, of which little attention has been paid on this issue. In this study, laboratory experiment and cracking analysis were performed on an expansive soil. Crack patterns were quantitatively analyzed using the fractal concept. The relationships among crack pattern, water loss, number of freeze–thaw cycles, and fractal dimension were discussed. It was found that crack patterns on the surface exhibit a hierarchical network structure that is fractal at a statistical level. Cracks induced by freeze–thaw cycles are shorter, more irregularly oriented, and slowly evolves from an irregularly rectilinear pattern towards a polygonal or quasi–hexagonal one; water loss, closely related to specimen thickness, plays a significant role in the process of soil cracking; crack development under freeze-thaw cycles are not only attributed to capillary effect, but also to expansion and absorption effects.
  • Proline and soluble sugars accumulation in three pepper species (Capsicum spp) in response to water stress imposed at different stages of growth
  • Gideon O. Okunlola, Richard O. Akinwale, Adekunle A. Adelusi
  • DOI:10.3724/SP.J.1226.2016.00205
  • 2016, 8 (3): 205–211 Abstract (90) PDF (325 KB) (105)
  • Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W1),once in every three days (W2),once in every five days (W3),and zero water supplied throughout growing period (W0) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan's multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants.
  • 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 (103) HTML (10) PDF (34922 KB) (95)
  • 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.

  • High-resolution mass spectrometric characterization of dissolved organic matter from warm and cold periods in the NEEM ice core
  • JianZhong Xu, Amanda Grannas, CunDe Xiao, ZhiHeng Du, Amanda Willoughby, Patrick Hatcher, YanQing An
  • DOI:10.3724/SP.J.1226.2018.00038
  • 2018, 10 (1): 38–46 Abstract (72) PDF (3711 KB) (94)
  • Dissolved organic matter (DOM) is an important component of ice cores but is currently poorly characterized. DOM from one Holocene sample (HS, aged at 1600-4500 B.P.) and one Last Glacial Maximum sample (LS, aged at 21000-25000 B.P.) from the North Greenland Eemian Ice Drilling (NEEM) ice core were analyzed by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). CHO compounds contributed 50% of the compounds identified in negative-ionization mode in these two samples, with significant contributions from organic N, S, and P compounds, likely suggesting that marine DOM was an important source in these samples. Overall, the chemical compositions are similar between these two samples, suggesting their consistent DOM sources. However, subtle differences in the DOM between these two samples are apparent and could indicate differences in source strength or chemistry occurring through both pre- and post-depositional processes. For example, higher relative amounts of condensed carbon compounds in the HS DOM (5%), compared to the LS DOM (2%), suggest potentially important contributions from terrestrial sources. Greater incorporation of P in the observed DOM in the LS DOM (22%), compared to the HS DOM (13%), indicate more active microbiological processes that likely contribute to phosphorus incorporation into the DOM pool. Although these two samples present only a preliminary analysis of DOM in glacial/interglacial periods, the data indicate a need to expand the analysis into a broader range of ice-core samples, geographical locations, and glacial/interglacial periods.
  • Effects of heavy metal (Pb) concentration on some growth parameters of plants grown in lead polluted soil under organic fertilizer amendment
  • Ojo M. Oseni, Adekunle A. Adelusi, Esther O. Dada, Abdulfatai B. Rufai
  • DOI:10.3724/SP.J.1226.2016.00036
  • 2016, 8 (1): 36–45 Abstract (61) PDF (303 KB) (94)
  • This study investigated morphological variation and biomass accumulation that occurred in Sida acuta and Chromolaena odorata plants grown in lead polluted soil under organic fertilizer amendment. The study was carried out in the screen house at the Biological Gardens of the Obafemi Awolowo University, Ile-Ife, Osun State. The experiment was a factorial combination of one heavy metal (Pb) at five levels of concentration (0, 200, 400, 800 and 1,000 mg/kg) in a completely randomized design, and were replicated three times for each of the two plants and two levels (0 g/kg and 9.4 g/kg) of organic fertilizer (OBD-Plus). Each pot was filled with 5 kg of air-dried and sieved soil and placed on a plastic tray for the collection of excess water. Two weeks after planting, seedlings of uniform height were transplanted from the nursery to experimental pots at the rate of one seedling per pot and grown for 10 weeks. The growth parameters of the plants were biomonitored for 7 weeks. After 10 weeks of treatment, the plants were harvested and dried to calculate the biomass accumulation. The two plant species performed better under fertilizer application than without it. For each of the plant species the growth parameters decreased as the levels of Pb concentration increased. Furthermore, the plants' biomass decreased significantly (p<0.05) as the levels of Pb concentration increased. The organic fertilizer helped to improve the plants' performance in lead-polluted soil.
  • Influence of fines content on the anti-frost properties of coarse-grained soil
  • TianLiang Wang, ZuRun Yue, TieCheng Sun, JinChuang Hua
  • DOI:10.3724/SP.J.1226.2015.00407
  • 2015, 7 (4): 407–413 Abstract (57) PDF (4001 KB) (94)
  • This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines; (2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw; (3) with increasing numbers of freeze-thaw cycles,the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and (4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions.
  • Characteristics of climate and melt runoff in the Koxkar Glacier River Basin, south slope of the Tianshan Mountains, Northwest China
  • Min Xu,HaiDong Han,ShiChang Kang,Hua Tao
  • DOI:10.3724/SP.J.1226.2019.00435.
  • 2019, 11 (6): 435–447 Abstract (53) HTML (7) PDF (5258 KB) (94)
  • Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May, reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m3 during the four years observed, with 87.0% occurring in the ablation season (May-September). During the study period, the runoff in August accounted for 29% of total streamflow, followed by July (22%) and June (14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier (0.66-0.76). The daily depth of runoff to daily temperature and daily water vapor pressure had an R 2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R 2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.

  • Numerical analysis on the thermal regimes of thermosyphon embankment in snowy permafrost area
  • Yan Lu, Xin Yi, WenBing Yu, WeiBo Liu
  • DOI:10.3724/SP.J.1226.2017.00580
  • 2017, 9 (6): 580–586 Abstract (122) PDF (1972 KB) (93)
  • Snow covers the road embankments in winter in high latitude permafrost zones. The effect of snow cover on embankments was simulated based on field measurements of boundary conditions and initial ground temperature profile in Mohe, China. The effect of thermosyphons on the embankment warmed by snow cover was evaluated by numerical simulations as well. The results indicate that the difference of thermal regimes between non-thermosyphon and thermosyphon embankments reaches to 22 m in depth below the ground surface. It is much warmer in the non-thermosyphon embankment body in winter. Affected by the snow cover, heat flux gradually spreads into the deep ground of the subgrade over time. The permafrost table under the slope toe of a thermosyphon embankment is 1.2 m higher than that of a non-thermosyphon embankment in the 20th year. In addition, the permafrost table at the slope toe of a thermosyphon embankment is 26 cm deeper over 20 years. These results indicate that thermosyphons can greatly weaken the warm effect of snow cover. However, thermosyphons cannot avoid the degradation of permafrost under the scenarios of snow cover. Therefore, composite measures need to be adopted to keep embankment stability in snowy permafrost zones.
  • A mathematical approach to evaluate maximum frost heave of unsaturated silty clay
  • Lin Geng, XianZhang Ling, Liang Tang, Jun Luo, XiuLi Du
  • DOI:10.3724/SP.J.1226.2017.00438
  • 2017, 9 (5): 438–446 Abstract (96) PDF (2776 KB) (93)
  • Maximum frost heave of unsaturated frost-susceptible soils, in conjunction with a high water table, is an important consideration for the design of foundations in seasonally frozen regions. Therefore, it is necessary to evaluate accurately and efficiently the maximum frost heave for a given soil. For this purpose, a series of one-sided freezing experiments was conducted on unsaturated silty clay in an open system. Multistage cooling of sufficient duration was applied to the soil sample's top, while constant above-zero temperatures were maintained at the bottom. Then, a simple methodology for calculating maximum frost heave at a given cooling temperature was derived utilizing information obtained within the limited time allotted for each stage. On this basis, an empirical equation for defining maximum frost heave as a function of cooling temperature and overburden pressure was determined. Overall, this study provides a simple and practical procedure that is applicable to the evaluation of maximum frost heave of unsaturated frost-susceptible soils.
  • An Arthrobacter strain isolated from desert soils in the region of Shule River (China) can convert cellulose to potential biofuels
  • Constantine Uwaremwe, ShiWeng Li, XiMing Chen, Maurice Ngabire, Tawheed Mohammed Elheesin Shareef, Juan Li, MingHui Wu, GuoLi Li
  • DOI:10.3724/SP.J.1226.2017.00167
  • 2017, 9 (2): 167–174 Abstract (72) PDF (4706 KB) (91)
  • In this study, an Arthrobacter strain from desert soils in the Shule River Valley was isolated, China, which has a strong ability to convert cellulose to potential biofuel. In total, from five soil sample sites, six strains were isolated that grew well on CMC-Agar medium, with colony diameters ranging from 3~4 mm, among them, one strain had a strong ability to produce biofuels. Based on morphological and phylogenetic analyses, the isolate was identified as Arthrobacter nitroguajacolicus strain SLP1. The chemical properties of the biofuel extracted from the fermentation broth of strain SLP1 were analysed by gas chromatography and mass spectrometry. A total of 41 kinds of carbon compounds were identified, of those, five were detected at peak concentration and the carbon numbers ranged from C16- C22, which can be classified as alkanes, alkenes, and alcohols. Furthermore, biofuel-producing ability of strain SLP1 was enhanced using NTG mutagen. In a total of 94 mutant strains, four show the most enhanced biofuel production relative to the original strain. Biofuel production conditions were optimized by growing the four mutant strains on LB-Agar and SS-Agar medium.
  • The simulation of LUCC based on Logistic-CA-Markov model in Qilian Mountain area, China
  • HaiJun Wang, XiangDong Kong, Bo Zhang
  • DOI:10.3724/SP.J.1226.2016.00350
  • 2016, 8 (4): 350–358 Abstract (117) PDF (3422 KB) (91)
  • The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that:(1) Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. (2) For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution (weight) of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. (3) In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years (2015-2042), farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.
  • 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 (86) HTML (5) PDF (784 KB) (91)
  • 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.

  • Characteristics of permafrost degradation in Northeast China and its ecological effects: A review
  • ShanShan Chen,ShuYing Zang,Li Sun
  • DOI:10.3724/SP.J.1226.2020.00001.
  • 2020, 12 (1): 1–11 Abstract (105) HTML (16) PDF (1207 KB) (91)
  • Latitudinal permafrost in Northern Northeast (NNE) China is located in the southern margin of the Eurasian continent, and is very sensitive to climatic and environmental change. Numerical simulations indicate that air temperature in the permafrost regions of Northeast China has been on the rise since the 1950s, and will keep rising in the 21st century, leading to extensive degradation of permafrost. Permafrost degradation in NNE China has its own characteristics, such as northward shifts in the shape of a "W" for the permafrost southern boundary (SLP), discontinuous permafrost degradation into island-like frozen soil, and gradually disappearing island permafrost. Permafrost degradation leads to deterioration of the ecological environment in cold regions. As a result, the belt of larch forests dominated by Larix gmelinii has shifted northwards and wetland areas with symbiotic relationships with permafrost have decreased significantly. With rapid retreat and thinning of permafrost and vegetation change, the CO2 and CH4 flux increases with mean air temperature from continuous to sporadic permafrost areas as a result of activity of methanogen enhancement, positively feeding back to climate warming. This paper reviews the features of permafrost degradation, the effects of permafrost degradation on wetland and forest ecosystem structure and function, and greenhouse gas emissions on latitudinal permafrost in NNE China. We also put forward critical questions about the aforementioned effects, including: (1) establish long-term permafrost observation systems to evaluate the distribution of permafrost and SLP change, in order to study the feedback of permafrost to climate change; (2) carry out research about the effects of permafrost degradation on the wetland ecosystem and the response of Xing'an larch to global change, and predict ecosystem dynamics in permafrost degradation based on long-term field observation; (3) focus intensively on the dynamics of greenhouse gas flux in permafrost degradation of Northeast China and the feedback of greenhouse gas emissions to climate change; (4) quantitative studies on the permafrost carbon feedback and vegetation carbon feedback due to permafrost change to climate multi-impact and estimate the balance of C in permafrost regions in the future.

  • Photosynthetic pigments accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress
  • Ezekiel Dare Olowolaju, Adekunle Ajayi Adelusi
  • DOI:10.3724/SP.J.1226.2017.00120
  • 2017, 9 (2): 120–126 Abstract (65) PDF (2148 KB) (90)
  • This study aimed at investigating the photosynthetic pigment accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress. The study was carried out under a screen-house to minimize extraneous factors such as pests and rodents using a randomized complete block design (RCBD). Seeds of cowpea, maize and tomato were collected from the Department of Crop Production and Protection, Faculty of Agriculture, Obafemi Awolowo University, Ile Ife, Osun state, Nigeria. These seeds were planted at a depth of about 3 mm below the soil. The seeds were sown at the rate of six seeds per pot in the monoculture, while in the pots designed for the mixed culture of maize and cowpea, maize and tomato, cowpea and tomato, three seeds of each plant were sown. Two seeds of each plant were sown in the pots with the three crops. The treatments were then supplied with 500 mL of tap water in the morning and in the evening respectively until the seedlings become fully established. The photosynthetic pigments were determined spectrophotometrically with three replicates. Plant growth indices were determined according to Hunts (1978) using leaf area and dry matter data collected at four and six weeks after planting. Statistical analysis was performed using statistical analytical software SAS version 9.2. The results indicated that photosynthetic pigments accumulation (Chlorophyll a, b and carotenoid) in maize (15.98, 23.92 and 44.72 μM), Chlorophyll b and carotenoid in tomato plants (12.48 and 1,178.7 μM) in the sole stands were more than the mixed culture of maize with cowpea and tomato (7.195, 14.74 and 0.00 μM). Also, total Chlorophyll in maize (1,127.8 μM), Chlorophyll a and total Chlorophyll in tomato (3.95 and 1,317.5 μM) in the mixed culture were more than in the sole culture of maize (1,030.9 μM) and tomato plants (-9.40 and 546.3 μM). The different photosynthetic pigments accumulated in cowpea were greatly enhanced in the mixed culture than in the sole culture. All the photosynthetic pigments of maize, cowpea and tomato in all the treatments analysed in this study were significantly different at P>0.05. Plant growth indices such as net assimilation rate, relative growth rate, crop growth rate and tissue water contents of these plants had higher value in the intercropped than the check crop (sole). These plant growth indices were significantly different to one another at P>0.05. This study concluded that competition for shared resources in the mixed culture of tomato, maize and cowpea enhanced growth and accumulation of photosynthetic pigments.
  • Origin and advances in implementing blowing-snow effects in the Community Land Model
  • ZeYong Hu,ZhiPeng Xie
  • DOI:10.3724/SP.J.1226.2019.00335.
  • 2019, 11 (5): 335–339 Abstract (101) HTML (14) PDF (938 KB) (90)
  • now cover on the Tibetan Plateau (TP) is closely related to regional and continental biological and hydrological processes. The vast snow cover, special climatic conditions, and sparse vegetative cover over the TP facilitate the occurrence of blowing snow, leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer. However, blowing-snow processes are significantly misrepresented or even neglected in current models, which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain. We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model. These studies can be divided into three parts: detection of the problems, development of the land-surface model, and application of the coupled model over the TP (the logical framework is presented in Figure 1). The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein; and the importance of blowing-snow processes in the land-surface model, especially over the TP, is highlighted. We expect that the blowing-snow studies over the TP will play a key role in documenting and understanding the land-surface processes (LSPs) and the cryospheric changes over the TP.

  • Thermal influence of ponding and buried warm-oil pipelines on permafrost: a case study of the China-Russia Crude Oil Pipeline
  • YanHu Mu,MingTang Chai,GuoYu Li,Wei Ma,Fei Wang,YaPeng Cao
  • DOI:10.3724/SP.J.1226.2020.00059.
  • 2020, 12 (2): 59–70 Abstract (77) HTML (14) PDF (7664 KB) (89)
  • Buried pipelines are widely used for transporting oil in remote cold regions. However, the warm oil can induce considerable thermal influence on the surrounding frozen soils and result in severe maintenance problems. This paper presents a case study of the thermal influence of ponding and buried warm-oil pipelines on permafrost along the China-Russia Crude Oil Pipeline (CRCOP) in Northeast China. Since its operation in 2011, the operation of the warm-oil pipelines has led to rapid warming and thawing of the surrounding permafrost and development of sizable ponding along the pipeline route, which, in return, exacerbates the permafrost degradation. A field study was conducted along a 400-km long segment of the CRCOP in permafrost regions of Northeast China to collect the location and size information of ponding. A two-dimensional heat transfer model coupled with phase change was established to analyze the thermal influence of ponding and the operation of warm-oil pipelines on the surrounding permafrost. In-situ measured ground temperatures from a monitoring site were obtained to validate the numerical model. The simulation results show that ponding accelerates the development of the thaw bulb around the pipeline. The maximum thaw depth below the pipeline increases from 4 m for the case without ponding to 9 m for the case with ponding after 50 years of operation, and ponding directly above the pipe induces the maximum thaw depth. Engineering measures should be adopted to control the size or even eliminate surface water-rich ponding for the long-term performance of buried warm-oil pipelines.

  • Comparative studies on leaf epidermal micromorphology and mesophyll structure of Elaeagnus angustifolia L. in two different regions of desert habitat
  • MengMeng Li, YuBing Liu, MeiLing Liu, Dan Liu
  • DOI:10.3724/SP.J.1226.2015.00229
  • 2015, 7 (3): 229–237 Abstract (52) PDF (1449 KB) (88)
  • In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses of Elaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy (SEM), and mesophyll structure was studied by light microscopy (LM) and transmission electron microscopy (TEM). Materials were selected from Linze County, Gansu Province (material A) and Qitai County, Xinjiang Uygur Autonomous Region (material B) of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in material A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stellate-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford resistance to environmental stress.
  • 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 (87) HTML (4) PDF (1767 KB) (87)
  • 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.

  • Comparative foliar anatomy of three Khaya species (Meliaceae) used in Nigeria as antisickling agent
  • Ololade A. Oyedapo,Joseph M. Agbedahunsi,H. C Illoh,Akinwumi J. Akinloye
  • DOI:10.3724/SP.J.1226.2018.00279
  • 2018, 10 (4): 279–285 Abstract (110) HTML (9) PDF (1820 KB) (86)
  • Khaya belongs to the family Meliaceae. In Nigeria the genus is represented by three species viz; K. senegalensis A. Juss., K. grandifoliola C. DC. and K. ivorensis A. Chev. Comparative foliar anatomy of the three Khaya species was carried out to identify and describe distinctive anatomical characters that could possibly be used to delimit the three taxa. Transverse section, epidermal peels and cleared leaves of these three species were made. Characteristic similarity and disparity in the tissues arrangement as well as cell inclusions were noted for description and delimitation. The three Khaya species studied had essentially the same anatomical features, e.g., venation pattern having open polygonal areoles and the veins terminals biforkated. However, there were characters that seem to be species specific, e.g., vien termination number and areole width. The leaf epidermal studies of the three species revealed similarities in stomatal type which are generally staurocytic, epidermal cells and undulating anticlinal cell walls but stomata density varied. Hexacytic stomata is only observed in the abaxial surface of K. grandifoliola which distinguished this species from the others. The leaf petiole shape of the three species are round and difficult to distinguish into adaxial and abaxial surfaces. The cuticle is striated, vascular bundles are heart shape, conjoint, concentric and amphivasal, but are different in epidermal and collenchyma cell layer numbers. The leaf transverse sections of the three Khaya species studied have conjoint, concentric and amphicribral bundles while the leaf cuticle of K. senegalensis and K. grandifoliola are striated but that of Khaya ivorensis is non-striated.

  • Surface-deformation monitoring in the permafrost regions over the Tibetan Plateau, using Sentinel-1 data
  • ZhenMing Wu, Lin Zhao, Lin Liu, Rui Zhu, ZeShen Gao, YongPing Qiao, LiMing Tian, HuaYun Zhou, MeiZhen Xie
  • DOI:10.3724/SP.J.1226.2018.00114
  • 2018, 10 (2): 114–125 Abstract (86) PDF (2925 KB) (85)
  • Differential Interferometric Synthetic Aperture Radar (D-InSAR) has been widely used to measure surface deformation over the Tibetan Plateau. However, the accuracy and applicability of the D-InSAR method are not well estimated due to the lack of in-situ validation. In this paper, we mapped the seasonal and long-term displacement of Tanggula (TGL) and Liangdaohe (LDH) permafrost regions with a stack of Sentinel-1 acquisitions using the Small Baseline Subset InSAR (SBAS-InSAR) method. In the TGL region, with its dry soils and sparse vegetation, the InSAR-derived surface-deformation trend was consistent with ground-based leveling results; long-term changes of the active layer showed a settlement rate of around 1 to 3 mm/a due to the melting of ground ice, indicating a degrading permafrost in this area. Around half of the deformation was picked up on monitoring, in contrast with in-situ measurements in LDH, implying that the D-InSAR method remarkably underestimated the surface-deformation. This phenomenon may be induced by the large soil-water content, high vegetation coverage, or a combination of these two factors in this region. This study demonstrates that surface deformation could be mapped accurately for a specific region with Sentinel-1 C-band data, such as in the TGL region. Moreover, although the D-InSAR technology provides an efficient solution for broad surface-deformation monitoring in permafrost regions, it shows a poor performance in the region with high soil-water content and dense vegetation coverage.
  • Direct shear tests of coarse-grained fillings from high-speed railway subgrade in cold regions
  • QingZhi Wang, JianKun Liu, JianHong Fang, AnHua Xu
  • DOI:10.3724/SP.J.1226.2017.00236
  • 2017, 9 (3): 236–242 Abstract (63) PDF (3277 KB) (85)
  • In order to study the shear behavior of coarse-grained fillings taken from the subgrade bottom layer of a cold region high-speed railway, large scale direct shear tests were conducted with different normal pressures, water contents and temperatures. The results indicate that the relationship between shear displacement and shear stress changed from strain-softening at lower normal pressures to strain-hardening at higher normal pressures, in both unfrozen and frozen states. This phenomenon was mainly due to the shear dilatation deformation effect. The shear displacement-shear stress curves show similar stages. Besides, the shear stress rapidly increased and there was not an increment in the shear displacement during the initial stage of the shear process in the frozen state. In both the unfrozen or frozen states at the same water contents, the shear strength increased with increasing normal pressure.
  • Numerical simulation and experimental validation of moisture-heat coupling for saturated frozen soils
  • ZhiMing Li, Jian Chen, Kai Sun, Bin Zhang
  • DOI:10.3724/SP.J.1226.2017.00250
  • 2017, 9 (3): 250–257 Abstract (88) PDF (1039 KB) (85)
  • In seasonally frozen regions, freezing-and-thawing action is the main cause responsible for the destruction of canals, which is closely linked to the temperature gradient and water transport. To investigate the behaviour of soils under freezing-and-thawing actions, many numerical models have been established that consider the important coupling of moisture transport and temperature evolution; but they contain excessive parameters, some of which are rather difficult to determine. Based on the well-known Harlan's theory, a simple moisture-heat coupling model was recently proposed to quantify the coupled moisture-heat transport performance of soils in terms of the central temperature and porosity. The mathematical module of COMSOL Multiphysics was further employed to solve the governing equations numerically. To validate our model, a thorough experimental scheme was carried out in our lab. The measured temperature distribution was found to be consistent with the predicted results.
  • Soil hydraulic conductivity and its influence on soil moisture simulations in the source region of the Yellow River―take Maqu as an example
  • DongYu Jia,Jun Wen,Xin Wang,ZuoLiang Wang
  • DOI:10.3724/SP.J.1226.2019.00360.
  • 2019, 11 (5): 360–370 Abstract (78) HTML (7) PDF (2177 KB) (85)
  • aturated hydraulic conductivity and unsaturated hydraulic conductivity which are influenced by soil are two important factors that affect soil water transport. In this paper, data supplied by the Chinese Academy of Sciences are used to determine true unsaturated hydrology values. Furthermore, in combination with observed, model simulation and experimental data, an improved saturated hydraulic conductivity parameterization scheme is carried out in CLM4.5 at a single point in the summer. The main results show that: (1) After improving saturated hydraulic conductivity in CLM4.5 through a parameterization modification, it is found that shallow layer soil moisture increases compared to the initial value; and (2) The numerical values of unsaturated hydraulic conductivities in the model are obviously larger than experimental values. By substituting the Brooks-Corey soil water characteristic curve into the Mualem model, the value of unsaturated hydraulic conductivity is modified; (3) By using the modified value, it is found that the attenuating magnitude of simulated soil moisture caused by each rainfall event is reduced. The soil moisture variation in shallow layers (5, 10 and 20 cm) could be better displayed.

  • 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 (71) PDF (2066 KB) (84)
  • 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.
  • Characterization of landscape pattern based on land economic niche change: A case study in Ganzhou, Gansu Province, China
  • HuaLi Tong, PeiJi Shi, XueBin Zhang, ZaiYan Li
  • DOI:10.3724/SP.J.1226.2018.00261
  • 2018, 10 (3): 261–270 Abstract (53) PDF (1614 KB) (82)
  • Land use change has a profound impact on biodiversity and ecological processes, and is closely related to changes in landscape patterns. This paper introduces the theory and method of land economic niche into landscape ecology, which provides a new method for spatial characterization of urban and rural spatial landscape patterns. Based on this theory, this paper analyzes the landscape pattern of Ganzhou District by using Landsat images as data source in 1995, 2000, 2005, 2010 and 2015. We calculated the land economic niche by applying the niche potential theory. Combined with the theory of landscape ecology, we explored the effects of the land economic niche change on the landscape pattern at a county scale. The results show that economic niche of construction land, watershed and farmland increased during 1995-2015, and grassland declined significantly. The economic niche of farmland, construction land, watershed and grassland show a negative correlation with the number of patches (NP), fragmentation index (FN) and the fractal dimension index (FD), and had a positive correlation with the aggregation index (AI). There was no significant correlation between the forest land economic niche and landscape metrics. The change of land economic niche has a driving effect on the landscape pattern of the county, which can represent the economic development direction of Ganzhou District. The land economic niche is closely related to the landscape type which can directly obtain an economic benefit.
  • Seed germination and seedling growth of Pycnanthus angolensis (Welw.) Warb., African false nutmeg
  • Sakpere A.M.A.
  • DOI:10.3724/SP.J.1226.2019.00350.
  • 2019, 11 (5): 350–359 Abstract (107) HTML (150) PDF (2153 KB) (221)
  • This study investigated the germination behavior and seedling growth of Pycnanthus angolensis seeds. The germination study was carried out in the laboratory and included pretreatment studies and observation of the seed-germination process. For each treatment, three replications of 20 seeds were sown in a transparent plastic germination box (12cm × 22cm × 5cm) lined with moistened filter paper at room temperature. To monitor seedling growth, seedlings were transplanted into pots filled with topsoil and laid out in a completely randomized design. Ten seedlings replicated thrice were measured monthly; and the shoot height, leaf area, and root length, as well as the fresh and dry weights of the seedlings, were recorded. Results showed that mechanically scarified seeds exhibited the significantly highest germination percent (83.33%, P <0.005), followed by control seeds (70.83%), whereas seeds treated with 98% sulphuric acid (H2SO4) displayed the lowest germination percent (1.67). The endospermous seeds exhibited cryptogeal germination, while seeds stored for a month (with or without arils) failed to germinate. During seed germination, radicle protrusion continued with a pseudo-opening of the root, through which the brownish cotyledonary petiole was emitted, thus releasing the plumule at the posterior position. Moreover, P. angolensis exhibited a slow growth rate, attaining a shoot height of 73 cm within a year. The highest positive change in leaf number and area was recorded in the fourth month, a period during which the least change in shoot height occurred. The study concluded that mechanical scarification of the seeds ensured significant and faster germination than chemical scarification or no treatment at all. Additionally, P. angolensis displayed a cryptogeal germination, with the seedling growth of the tree species observed to be slow.

  • Research on pile performance and state-of-the-art practice in cold regions
  • JianKun Liu, TengFei Wang, Zhi Wen
  • DOI:10.3724/SP.J.1226.2018.00001
  • 2018, 10 (1): 1–11 Abstract (181) PDF (3430 KB) (209)
  • A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows: (1) creep tests and bearing capacity, (2) frost-jacking hazards, (3) laterally loaded piles, (4) dynamic responses, (5) refreezing due to concrete-hydration heat, and (6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.
  • 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 (272) HTML (192) PDF (4797 KB) (179)
  • 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.

  • An evaluation of soil moisture from AMSR-E over source area of the Yellow River, China
  • TangTang Zhang,Mekonnen Gebremichael,Akash Koppa,XianHong Meng,Qun Du,Jun Wen
  • DOI:10.3724/SP.J.1226.2019.00461.
  • 2019, 11 (6): 461–469 Abstract (145) HTML (136) PDF (2806 KB) (147)
  • In this study, in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture products from NASA (National Aeronautics and Space Administration), JAXA (Japanese Aerospace Exploration Agency) and VUA (Vrije University Amsterdam and NASA) over Maqu County, Source Area of the Yellow River (SAYR), China. Results show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area, with a minimum RMSE (root mean square error) of 0.08 (0.10) m3/m3 and smallest absolute error of 0.07 (0.08) m3/m3 at the grassland area with ascending (descending) data. Therefore, the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR. The VUA soil moisture product shows that soil moisture presents a declining trend from east south (0.42 m3/m3) to west north (0.23 m3/m3), with good agreement with a general precipitation distribution. The center of SAYR presents extreme wetness (0.60 m3/m3) during the whole study period, especially in July, while the head of SAYR presents a high level soil moisture (0.23 m3/m3) in July, August and September.

  • Soil freezing process and different expressions for the soil-freezing characteristic curve
  • JunPing Ren, Sai K. Vanapalli, Zhong Han
  • DOI:10.3724/SP.J.1226.2017.00221
  • 2017, 9 (3): 221–228 Abstract (148) PDF (4411 KB) (132)
  • The soil-freezing characteristic curve (SFCC), which represents the relationship between unfrozen water content and sub-freezing temperature (or suction at ice-water interface) in a freezing soil, can be used for understanding the transportation of heat, water, and solute in frozen soils. In this paper, the soil freezing process and the similarity between the SFCC of saturated frozen soil and soil-water characteristic curve (SWCC) of unfrozen unsaturated soil are reviewed. Based on similar characteristics between SWCC and SFCC, a conceptual SFCC is drawn for illustrating the main features of soil freezing and thawing processes. Various SFCC expressions from the literature are summarized. Four widely used expressions (i.e., power relationship, exponential relationship, van Genuchten 1980 equation and Fredlund and Xing 1994 equation) are evaluated using published experimental data on four different soils (i.e., sandy loam, silt, clay, and saline silt). Results show that the exponential relationship and van Genuchten (1980) equation are more suitable for sandy soils. The simple power relationship can be used to reasonably best-fit the SFCC for soils with different particle sizes; however, it exhibits limitations when fitting the saline silt data. The Fredlund and Xing (1994) equation is suitable for fitting the SFCCs for all soils studied in this paper.
  • Qualitative and quantitative phytochemical analysis of selected mosses with different alcoholic solvents
  • Kehinde O. Olasoji,Amos M. Makinde,Bolajoko A. Akinpelu,Musibau O. Isa
  • DOI:10.3724/SP.J.1226.2019.00382.
  • 2019, 11 (5): 382–388 Abstract (67) HTML (8) PDF (670 KB) (132)
  • This study was conducted to investigate the qualitative and quantitative phytochemical content of the crude extracts of Archidium ohioense, Pelekium gratum, and Hyophila involuta with different alcoholic solvents (ethanol, methanol, Seaman's Schnapps, fresh oil-palm wine, and fresh Raffia-palm wine). The mosses were collected from their natural populations on the central campus of the Obafemi Awolowo University, Ile-Ife, Nigeria. The yield of the extracts was weighed for all the solvents, and the qualitative and quantitative evaluations of the extracts were carried out using standard methods. The results of phytochemical analysis of the crude extracts from the mosses showed the presence of saponins, cardiac glycosides, triterpenes, alkaloids, flavonoids, and steroids. The quantitative phytochemical analysis of the crude extracts showed that ethanolic extracts of Hyophila involuta had the highest flavonoid content (288.37±0.10 mg RE/g), and Raffia-palm-wine extracts of Hyophila involuta had the highest saponin content (224.70±0.02 mg/g), while the methanolic extract of Archidium ohioense had the highest cardiac glycosides content (63.71±0.14 mg/g), and the Raffia-palm wine extract of Hyophila involuta had the highest alkaloids content (102.50±0.12 mg/g). Raffia- and oil-palm wines were observed to be the most effective solvents for all the mosses studied, followed by Seaman's Schnapp, while methanol and ethanol were less effective. The study concluded that the extracts of the mosses studied contain pharmacologically active constituents that can be used for therapeutic purposes.

  • Comparative study of probable maximum precipitation and isohyetal maps for mountainous regions, Pakistan
  • Muhammad Waseem Boota, Ghulam Nabi, Tanveer Abbas, HuiJun Jin, Ayesha Yousaf, Muhammad Azeem Boota
  • DOI:10.3724/SP.J.1226.2018.00055
  • 2018, 10 (1): 55–68 Abstract (74) PDF (4789 KB) (126)
  • Probable maximum precipitation (PMP) is widely used by hydrologists for appraisal of probable maximum flood (PMF) used for soil and water conservation structures, and design of dam spillways. A number of methods such as empirical, statistical and dynamic are used to estimate PMP, the most favored being statistical and hydro-meteorological. In this paper, PMP estimation in mountainous regions of Pakistan is studied using statistical as well as physically based hydro-meteorological approaches. Daily precipitation, dew point, wind speed and temperature data is processed to estimate PMP for a one-day duration. Maximum precipitation for different return periods is estimated by using statistical approaches such as Gumble and Log-Pearson type-III (LP-III) distribution. Goodness of fit (GOF) test, chi-square test, correlation coefficient and coefficient of determination were applied to Gumble and LP-III distributions. Results reveal that among statistical approaches, Gumble distribution performed the best result compared to LP-III distribution. Isohyetal maps of the study area at different return periods are produced by using the GIS tool, and PMP in mountainous regions varies from 150 to 320 mm at an average value of 230.83 mm. The ratio of PMP for one-day duration to highest observed rainfall (HOR) varied from 1.08 to 1.29 with an average value of 1.18. An appropriate frequency factor (Km) is very important which is a function of mean for observed precipitation and PMP for 1-day duration, and Km values varies from 2.54 to 4.68. The coefficient of variability (Cv) varies from minimum value of 28% to maximum value of 43.35%. It was concluded that the statistical approach gives higher results compared to moisture maximization (MM) approach. In the hydro-meteorological approach, moisture maximization (MM) and wind moisture maximization (WMM) techniques were applied and it was concluded that wind moisture maximization approach gives higher results of PMP as compared to moisture maximization approach as well as for Hershfield technique. Therefore, it is suggested that MM approach is the most favored in the study area for PMP estimation, which leads to acceptable results, compared to WMM and statistical approaches.
  • Relationship between ponding and topographic factors along the China-Russia Crude Oil Pipeline in permafrost regions
  • MingTang Chai,YanHu Mu,GuoYu Li,Wei Ma,Fei Wang
  • DOI:10.3724/SP.J.1226.2019.00419.
  • 2019, 11 (6): 419–427 Abstract (111) HTML (15) PDF (4231 KB) (122)
  • The original landform along the China-Russia Crude Oil Pipeline (CRCOP, line 2) was disturbed during installation of pavement for the pipeline. Forest and vegetation coverage is dense, and runoff develops along the pipe. Since the operation of the CRCOP (line 2) began in 2018, ponding has appeared on both sides of the pipeline. If there is no drainage, ponding can hardly dissipate, due to the low permeability of the permafrost layer. With the supply of surface flow and the transportation of oil at positive temperatures, ponding promotes an increase in temperature and changes the boundary thermal conditions of the pipeline. Meanwhile, when the ponding freezes and thaws, frost heave threatens operational safety of the pipeline. Furthermore, the ponding can affect the thermal condition of line 1. In this paper, the distribution of ponding along the CRCOP was obtained by field investigation. The type and cause of ponding were summarized, and the catchment and stream order were extracted by the Digital Elevation Model (DEM). According to the statistical results in attributes for topographic factors, it is known that ponding along the pipeline is relative to elevation, slope, aspect, and the Topographic Wetness Index (TWI). Water easily accumulates at altitudes of 300-450 m, slopes within 3°-5°, aspect in the northeast or south, TWI within 13-16, flow direction in north-east-south, and flow length within 90-150 km. This paper proposes a theoretical basis for the cause and characteristics of ponding along the pipeline.

  • Cutting of Phragmites australis as a lake restoration technique: Productivity calculation and nutrient removal in Wuliangsuhai Lake, northern China
  • Jan Felix Köbbing, Niels Thevs, Stefan Zerbe
  • DOI:10.3724/SP.J.1226.2016.00400
  • 2016, 8 (5): 400–410 Abstract (68) PDF (2545 KB) (118)
  • Reed is one of the most frequent and dominant species in wetlands all over the world, with common reed (Phragmites australis (Cav.) Trin. ex Steud.) as the most widely distributed species. In many wetlands, P. australis plays a highly ambivalent role. On the one hand, in many wetlands it purifies wastewater, provides habitat for numerous species, and is a potentially valuable raw material, while on the other hand it is an invasive species which expands aggressively, prevents fishing, blocks ditches and waterways, and builds monospecies stands. This paper uses the eutrophic reed-swamp of Wuliangsuhai Lake in Inner Mongolia, northern China, as a case to present the multiple benefits of regular reed cutting. The reed area and aboveground biomass production are calculated based on field data. Combined with data about water and reed nutrient content, the impact of reed cutting on the lake nutrient budget (N and P) is investigated. Currently, at this lake around 100,000 tons of reed are harvested in winter annually, removing 16% and 8% of the total nitrogen and phosphorus influx, respectively. Harvesting all available winter reed could increase the nutrient removal rates to 48% and 24%, respectively. We also consider the effects of summer harvesting, in which reed biomass removal could overcompensate for the nutrient influx but could potentially reduce reed regrowth.
  • A review on the ambit and prospects of C3 and C4 plants in Nigeria
  • Abdulwakeel Ayokun-nun Ajao, Oludare Oladipo Agboola, Sefiu Adekilekun Saheed
  • DOI:10.3724/SP.J.1226.2017.00587
  • 2017, 9 (6): 587–598 Abstract (50) PDF (2416 KB) (117)
  • 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.
  • 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 (74) HTML (6) PDF (4973 KB) (116)
  • 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.

  • Influence of proximity to the Qinghai-Tibet highway and railway on variations of soil heavy metal concentrations and bacterial community diversity on the Tibetan Plateau
  • Xia Zhao,JunFeng Wang,Yun Wang,Xiang Lu,ShaoFang Liu,YuBao Zhang,ZhiHong Guo,ZhongKui Xie,RuoYu Wang
  • DOI:10.3724/SP.J.1226.2019.00407.
  • 2019, 11 (6): 407–418 Abstract (96) HTML (14) PDF (4670 KB) (116)
  • An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway (QTH) revealed that the accumulation of heavy metals (over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway (QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria. The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR (MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR (MA/WA sampling sites). The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.

  • Measurement for coordinated development of "four modernizations" and its efficiency of prefecture level cities or above in China
  • JingHu Pan, YanXing Hu
  • DOI:10.3724/SP.J.1226.2016.00163
  • 2016, 8 (2): 163–176 Abstract (56) PDF (697 KB) (113)
  • The efficient and coordinated development of industrialization,urbanization,informatization and agricultural modernization(so called "Sihua Tongbu" in China,and hereinafter referred to as "four modernizations") is not only a practical need but also an important strategic direction of integrating urban-rural development and regional development in recent China.This paper evaluated the comprehensive,coupling and coordinated developmental indices of "four modernizations" of China's 343 prefecture-level administrative units,and calculated their efficiency of "four modernizations" in 2001 and 2011.The efficiency evaluation index system was established.The efficiencies and their changing trend during the period 2001-2011 were investigated using the data envelopment analysis(DEA) model.Spatial-temporal pattern of the efficiency of China's prefecture-level units was explored by using exploratory spatial data analysis(ESDA).Finally,the main influencing factors were revealed with the aid of geographically weighted regression(GWR) model.Results indicate that the comprehensive,coupling and coordinated developmental indices and efficiency of "four modernizations" of China's prefecture-level administrative units have obvious spatial differences and show diverse regional patterns.Overall,the efficiency is relatively low,and only few units with small urban populations and economic scale are in DEA efficiencies.The efficiency changing trends were decreasing during 2001-2011,with a transfer of high efficiency areas from inland to eastern coastal areas.The difference between urban and rural per capita investment in fixed assets boasts the greatest influence on the efficiency.
  • Analysis of structural characteristics and spatial distribution of the national intangible cultural heritage in China and its policy implications
  • BaiCui Xu,JingHu Pan
  • DOI:10.3724/SP.J.1226.2019.00389.
  • 2019, 11 (5): 389–406 Abstract (78) HTML (10) PDF (4506 KB) (107)
  • Based on an investigation of four published batches listing 3,140 national intangible cultural heritage (ICH) projects in China and using GIS and some quantitative analysis methods, the spatial structure was investigated and the characteristics and distribution discussed. The distribution of ICHs in China is agglomerative and spatially dependent. From the view of ICH type, each type is distributed in different places, for different reasons, with history being the most important one we found. Nationwide, high-density cores are located in the Beijing-Tianjin-Hebei region and the Yangtze River Delta region. High densities of ICH are concentrated in flat, water-rich regions where broad-leaved forests dominate plains and low mountain areas—areas that have fertile soil, pleasant weather, a long history of culture, ethnic agglomeration, and development. This paper suggests that development of the ICH should be based on discovering unknown items, to break the existing pattern of strong cohesion and high density, and to seek a balanced development of the whole.

  • Estimating interaction between surface water and groundwater in a permafrost region of the northern Tibetan Plateau using heat tracing method
  • TanGuang Gao,Jie Liu,TingJun Zhang,ShiChang Kang,ChuanKun Liu,ShuFa Wang,Mika Sillanpää,YuLan Zhang
  • DOI:10.3724/SP.J.1226.2020.00071.
  • 2020, 12 (2): 71–82 Abstract (94) HTML (7) PDF (4245 KB) (107)
  • Understanding the interaction between groundwater and surface water in permafrost regions is essential to study flood frequencies and river water quality, especially in the high latitude/altitude basins. The application of heat tracing method, based on oscillating streambed temperature signals, is a promising geophysical method for identifying and quantifying the interaction between groundwater and surface water. Analytical analysis based on a one-dimensional convective-conductive heat transport equation combined with the fiber-optic distributed temperature sensing method was applied on a streambed of a mountainous permafrost region in the Yeniugou Basin, located in the upper Heihe River on the northern Tibetan Plateau. The results indicated that low connectivity existed between the stream and groundwater in permafrost regions. The interaction between surface water and groundwater increased with the thawing of the active layer. This study demonstrates that the heat tracing method can be applied to study surface water-groundwater interaction over temporal and spatial scales in permafrost regions.

  • Cracking in an expansive soil under freeze–thaw cycles
  • Yang Lu, SiHong Liu
  • DOI:10.3724/SP.J.1226.2017.00392
  • 2017, 9 (4): 392–397 Abstract (120) PDF (2977 KB) (106)
  • Expansive soils located in cold regions can easily endure the action of frost heaving and cyclic freezing–thawing. Cracking can also occur in expansive clayey soils under freeze–thaw cycles, of which little attention has been paid on this issue. In this study, laboratory experiment and cracking analysis were performed on an expansive soil. Crack patterns were quantitatively analyzed using the fractal concept. The relationships among crack pattern, water loss, number of freeze–thaw cycles, and fractal dimension were discussed. It was found that crack patterns on the surface exhibit a hierarchical network structure that is fractal at a statistical level. Cracks induced by freeze–thaw cycles are shorter, more irregularly oriented, and slowly evolves from an irregularly rectilinear pattern towards a polygonal or quasi–hexagonal one; water loss, closely related to specimen thickness, plays a significant role in the process of soil cracking; crack development under freeze-thaw cycles are not only attributed to capillary effect, but also to expansion and absorption effects.
  • Proline and soluble sugars accumulation in three pepper species (Capsicum spp) in response to water stress imposed at different stages of growth
  • Gideon O. Okunlola, Richard O. Akinwale, Adekunle A. Adelusi
  • DOI:10.3724/SP.J.1226.2016.00205
  • 2016, 8 (3): 205–211 Abstract (90) PDF (325 KB) (105)
  • Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W1),once in every three days (W2),once in every five days (W3),and zero water supplied throughout growing period (W0) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan's multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants.
  • 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 (103) HTML (10) PDF (34922 KB) (95)
  • 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.

  • High-resolution mass spectrometric characterization of dissolved organic matter from warm and cold periods in the NEEM ice core
  • JianZhong Xu, Amanda Grannas, CunDe Xiao, ZhiHeng Du, Amanda Willoughby, Patrick Hatcher, YanQing An
  • DOI:10.3724/SP.J.1226.2018.00038
  • 2018, 10 (1): 38–46 Abstract (72) PDF (3711 KB) (94)
  • Dissolved organic matter (DOM) is an important component of ice cores but is currently poorly characterized. DOM from one Holocene sample (HS, aged at 1600-4500 B.P.) and one Last Glacial Maximum sample (LS, aged at 21000-25000 B.P.) from the North Greenland Eemian Ice Drilling (NEEM) ice core were analyzed by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). CHO compounds contributed 50% of the compounds identified in negative-ionization mode in these two samples, with significant contributions from organic N, S, and P compounds, likely suggesting that marine DOM was an important source in these samples. Overall, the chemical compositions are similar between these two samples, suggesting their consistent DOM sources. However, subtle differences in the DOM between these two samples are apparent and could indicate differences in source strength or chemistry occurring through both pre- and post-depositional processes. For example, higher relative amounts of condensed carbon compounds in the HS DOM (5%), compared to the LS DOM (2%), suggest potentially important contributions from terrestrial sources. Greater incorporation of P in the observed DOM in the LS DOM (22%), compared to the HS DOM (13%), indicate more active microbiological processes that likely contribute to phosphorus incorporation into the DOM pool. Although these two samples present only a preliminary analysis of DOM in glacial/interglacial periods, the data indicate a need to expand the analysis into a broader range of ice-core samples, geographical locations, and glacial/interglacial periods.
  • Effects of heavy metal (Pb) concentration on some growth parameters of plants grown in lead polluted soil under organic fertilizer amendment
  • Ojo M. Oseni, Adekunle A. Adelusi, Esther O. Dada, Abdulfatai B. Rufai
  • DOI:10.3724/SP.J.1226.2016.00036
  • 2016, 8 (1): 36–45 Abstract (61) PDF (303 KB) (94)
  • This study investigated morphological variation and biomass accumulation that occurred in Sida acuta and Chromolaena odorata plants grown in lead polluted soil under organic fertilizer amendment. The study was carried out in the screen house at the Biological Gardens of the Obafemi Awolowo University, Ile-Ife, Osun State. The experiment was a factorial combination of one heavy metal (Pb) at five levels of concentration (0, 200, 400, 800 and 1,000 mg/kg) in a completely randomized design, and were replicated three times for each of the two plants and two levels (0 g/kg and 9.4 g/kg) of organic fertilizer (OBD-Plus). Each pot was filled with 5 kg of air-dried and sieved soil and placed on a plastic tray for the collection of excess water. Two weeks after planting, seedlings of uniform height were transplanted from the nursery to experimental pots at the rate of one seedling per pot and grown for 10 weeks. The growth parameters of the plants were biomonitored for 7 weeks. After 10 weeks of treatment, the plants were harvested and dried to calculate the biomass accumulation. The two plant species performed better under fertilizer application than without it. For each of the plant species the growth parameters decreased as the levels of Pb concentration increased. Furthermore, the plants' biomass decreased significantly (p<0.05) as the levels of Pb concentration increased. The organic fertilizer helped to improve the plants' performance in lead-polluted soil.
  • Influence of fines content on the anti-frost properties of coarse-grained soil
  • TianLiang Wang, ZuRun Yue, TieCheng Sun, JinChuang Hua
  • DOI:10.3724/SP.J.1226.2015.00407
  • 2015, 7 (4): 407–413 Abstract (57) PDF (4001 KB) (94)
  • This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines; (2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw; (3) with increasing numbers of freeze-thaw cycles,the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and (4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions.
  • Characteristics of climate and melt runoff in the Koxkar Glacier River Basin, south slope of the Tianshan Mountains, Northwest China
  • Min Xu,HaiDong Han,ShiChang Kang,Hua Tao
  • DOI:10.3724/SP.J.1226.2019.00435.
  • 2019, 11 (6): 435–447 Abstract (53) HTML (7) PDF (5258 KB) (94)
  • Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May, reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m3 during the four years observed, with 87.0% occurring in the ablation season (May-September). During the study period, the runoff in August accounted for 29% of total streamflow, followed by July (22%) and June (14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier (0.66-0.76). The daily depth of runoff to daily temperature and daily water vapor pressure had an R 2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R 2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.

  • Numerical analysis on the thermal regimes of thermosyphon embankment in snowy permafrost area
  • Yan Lu, Xin Yi, WenBing Yu, WeiBo Liu
  • DOI:10.3724/SP.J.1226.2017.00580
  • 2017, 9 (6): 580–586 Abstract (122) PDF (1972 KB) (93)
  • Snow covers the road embankments in winter in high latitude permafrost zones. The effect of snow cover on embankments was simulated based on field measurements of boundary conditions and initial ground temperature profile in Mohe, China. The effect of thermosyphons on the embankment warmed by snow cover was evaluated by numerical simulations as well. The results indicate that the difference of thermal regimes between non-thermosyphon and thermosyphon embankments reaches to 22 m in depth below the ground surface. It is much warmer in the non-thermosyphon embankment body in winter. Affected by the snow cover, heat flux gradually spreads into the deep ground of the subgrade over time. The permafrost table under the slope toe of a thermosyphon embankment is 1.2 m higher than that of a non-thermosyphon embankment in the 20th year. In addition, the permafrost table at the slope toe of a thermosyphon embankment is 26 cm deeper over 20 years. These results indicate that thermosyphons can greatly weaken the warm effect of snow cover. However, thermosyphons cannot avoid the degradation of permafrost under the scenarios of snow cover. Therefore, composite measures need to be adopted to keep embankment stability in snowy permafrost zones.
  • A mathematical approach to evaluate maximum frost heave of unsaturated silty clay
  • Lin Geng, XianZhang Ling, Liang Tang, Jun Luo, XiuLi Du
  • DOI:10.3724/SP.J.1226.2017.00438
  • 2017, 9 (5): 438–446 Abstract (96) PDF (2776 KB) (93)
  • Maximum frost heave of unsaturated frost-susceptible soils, in conjunction with a high water table, is an important consideration for the design of foundations in seasonally frozen regions. Therefore, it is necessary to evaluate accurately and efficiently the maximum frost heave for a given soil. For this purpose, a series of one-sided freezing experiments was conducted on unsaturated silty clay in an open system. Multistage cooling of sufficient duration was applied to the soil sample's top, while constant above-zero temperatures were maintained at the bottom. Then, a simple methodology for calculating maximum frost heave at a given cooling temperature was derived utilizing information obtained within the limited time allotted for each stage. On this basis, an empirical equation for defining maximum frost heave as a function of cooling temperature and overburden pressure was determined. Overall, this study provides a simple and practical procedure that is applicable to the evaluation of maximum frost heave of unsaturated frost-susceptible soils.
  • An Arthrobacter strain isolated from desert soils in the region of Shule River (China) can convert cellulose to potential biofuels
  • Constantine Uwaremwe, ShiWeng Li, XiMing Chen, Maurice Ngabire, Tawheed Mohammed Elheesin Shareef, Juan Li, MingHui Wu, GuoLi Li
  • DOI:10.3724/SP.J.1226.2017.00167
  • 2017, 9 (2): 167–174 Abstract (72) PDF (4706 KB) (91)
  • In this study, an Arthrobacter strain from desert soils in the Shule River Valley was isolated, China, which has a strong ability to convert cellulose to potential biofuel. In total, from five soil sample sites, six strains were isolated that grew well on CMC-Agar medium, with colony diameters ranging from 3~4 mm, among them, one strain had a strong ability to produce biofuels. Based on morphological and phylogenetic analyses, the isolate was identified as Arthrobacter nitroguajacolicus strain SLP1. The chemical properties of the biofuel extracted from the fermentation broth of strain SLP1 were analysed by gas chromatography and mass spectrometry. A total of 41 kinds of carbon compounds were identified, of those, five were detected at peak concentration and the carbon numbers ranged from C16- C22, which can be classified as alkanes, alkenes, and alcohols. Furthermore, biofuel-producing ability of strain SLP1 was enhanced using NTG mutagen. In a total of 94 mutant strains, four show the most enhanced biofuel production relative to the original strain. Biofuel production conditions were optimized by growing the four mutant strains on LB-Agar and SS-Agar medium.
  • The simulation of LUCC based on Logistic-CA-Markov model in Qilian Mountain area, China
  • HaiJun Wang, XiangDong Kong, Bo Zhang
  • DOI:10.3724/SP.J.1226.2016.00350
  • 2016, 8 (4): 350–358 Abstract (117) PDF (3422 KB) (91)
  • The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that:(1) Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. (2) For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution (weight) of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. (3) In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years (2015-2042), farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.
  • 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 (86) HTML (5) PDF (784 KB) (91)
  • 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.

  • Characteristics of permafrost degradation in Northeast China and its ecological effects: A review
  • ShanShan Chen,ShuYing Zang,Li Sun
  • DOI:10.3724/SP.J.1226.2020.00001.
  • 2020, 12 (1): 1–11 Abstract (105) HTML (16) PDF (1207 KB) (91)
  • Latitudinal permafrost in Northern Northeast (NNE) China is located in the southern margin of the Eurasian continent, and is very sensitive to climatic and environmental change. Numerical simulations indicate that air temperature in the permafrost regions of Northeast China has been on the rise since the 1950s, and will keep rising in the 21st century, leading to extensive degradation of permafrost. Permafrost degradation in NNE China has its own characteristics, such as northward shifts in the shape of a "W" for the permafrost southern boundary (SLP), discontinuous permafrost degradation into island-like frozen soil, and gradually disappearing island permafrost. Permafrost degradation leads to deterioration of the ecological environment in cold regions. As a result, the belt of larch forests dominated by Larix gmelinii has shifted northwards and wetland areas with symbiotic relationships with permafrost have decreased significantly. With rapid retreat and thinning of permafrost and vegetation change, the CO2 and CH4 flux increases with mean air temperature from continuous to sporadic permafrost areas as a result of activity of methanogen enhancement, positively feeding back to climate warming. This paper reviews the features of permafrost degradation, the effects of permafrost degradation on wetland and forest ecosystem structure and function, and greenhouse gas emissions on latitudinal permafrost in NNE China. We also put forward critical questions about the aforementioned effects, including: (1) establish long-term permafrost observation systems to evaluate the distribution of permafrost and SLP change, in order to study the feedback of permafrost to climate change; (2) carry out research about the effects of permafrost degradation on the wetland ecosystem and the response of Xing'an larch to global change, and predict ecosystem dynamics in permafrost degradation based on long-term field observation; (3) focus intensively on the dynamics of greenhouse gas flux in permafrost degradation of Northeast China and the feedback of greenhouse gas emissions to climate change; (4) quantitative studies on the permafrost carbon feedback and vegetation carbon feedback due to permafrost change to climate multi-impact and estimate the balance of C in permafrost regions in the future.

  • Photosynthetic pigments accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress
  • Ezekiel Dare Olowolaju, Adekunle Ajayi Adelusi
  • DOI:10.3724/SP.J.1226.2017.00120
  • 2017, 9 (2): 120–126 Abstract (65) PDF (2148 KB) (90)
  • This study aimed at investigating the photosynthetic pigment accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress. The study was carried out under a screen-house to minimize extraneous factors such as pests and rodents using a randomized complete block design (RCBD). Seeds of cowpea, maize and tomato were collected from the Department of Crop Production and Protection, Faculty of Agriculture, Obafemi Awolowo University, Ile Ife, Osun state, Nigeria. These seeds were planted at a depth of about 3 mm below the soil. The seeds were sown at the rate of six seeds per pot in the monoculture, while in the pots designed for the mixed culture of maize and cowpea, maize and tomato, cowpea and tomato, three seeds of each plant were sown. Two seeds of each plant were sown in the pots with the three crops. The treatments were then supplied with 500 mL of tap water in the morning and in the evening respectively until the seedlings become fully established. The photosynthetic pigments were determined spectrophotometrically with three replicates. Plant growth indices were determined according to Hunts (1978) using leaf area and dry matter data collected at four and six weeks after planting. Statistical analysis was performed using statistical analytical software SAS version 9.2. The results indicated that photosynthetic pigments accumulation (Chlorophyll a, b and carotenoid) in maize (15.98, 23.92 and 44.72 μM), Chlorophyll b and carotenoid in tomato plants (12.48 and 1,178.7 μM) in the sole stands were more than the mixed culture of maize with cowpea and tomato (7.195, 14.74 and 0.00 μM). Also, total Chlorophyll in maize (1,127.8 μM), Chlorophyll a and total Chlorophyll in tomato (3.95 and 1,317.5 μM) in the mixed culture were more than in the sole culture of maize (1,030.9 μM) and tomato plants (-9.40 and 546.3 μM). The different photosynthetic pigments accumulated in cowpea were greatly enhanced in the mixed culture than in the sole culture. All the photosynthetic pigments of maize, cowpea and tomato in all the treatments analysed in this study were significantly different at P>0.05. Plant growth indices such as net assimilation rate, relative growth rate, crop growth rate and tissue water contents of these plants had higher value in the intercropped than the check crop (sole). These plant growth indices were significantly different to one another at P>0.05. This study concluded that competition for shared resources in the mixed culture of tomato, maize and cowpea enhanced growth and accumulation of photosynthetic pigments.
  • Origin and advances in implementing blowing-snow effects in the Community Land Model
  • ZeYong Hu,ZhiPeng Xie
  • DOI:10.3724/SP.J.1226.2019.00335.
  • 2019, 11 (5): 335–339 Abstract (101) HTML (14) PDF (938 KB) (90)
  • now cover on the Tibetan Plateau (TP) is closely related to regional and continental biological and hydrological processes. The vast snow cover, special climatic conditions, and sparse vegetative cover over the TP facilitate the occurrence of blowing snow, leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer. However, blowing-snow processes are significantly misrepresented or even neglected in current models, which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain. We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model. These studies can be divided into three parts: detection of the problems, development of the land-surface model, and application of the coupled model over the TP (the logical framework is presented in Figure 1). The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein; and the importance of blowing-snow processes in the land-surface model, especially over the TP, is highlighted. We expect that the blowing-snow studies over the TP will play a key role in documenting and understanding the land-surface processes (LSPs) and the cryospheric changes over the TP.

  • Thermal influence of ponding and buried warm-oil pipelines on permafrost: a case study of the China-Russia Crude Oil Pipeline
  • YanHu Mu,MingTang Chai,GuoYu Li,Wei Ma,Fei Wang,YaPeng Cao
  • DOI:10.3724/SP.J.1226.2020.00059.
  • 2020, 12 (2): 59–70 Abstract (77) HTML (14) PDF (7664 KB) (89)
  • Buried pipelines are widely used for transporting oil in remote cold regions. However, the warm oil can induce considerable thermal influence on the surrounding frozen soils and result in severe maintenance problems. This paper presents a case study of the thermal influence of ponding and buried warm-oil pipelines on permafrost along the China-Russia Crude Oil Pipeline (CRCOP) in Northeast China. Since its operation in 2011, the operation of the warm-oil pipelines has led to rapid warming and thawing of the surrounding permafrost and development of sizable ponding along the pipeline route, which, in return, exacerbates the permafrost degradation. A field study was conducted along a 400-km long segment of the CRCOP in permafrost regions of Northeast China to collect the location and size information of ponding. A two-dimensional heat transfer model coupled with phase change was established to analyze the thermal influence of ponding and the operation of warm-oil pipelines on the surrounding permafrost. In-situ measured ground temperatures from a monitoring site were obtained to validate the numerical model. The simulation results show that ponding accelerates the development of the thaw bulb around the pipeline. The maximum thaw depth below the pipeline increases from 4 m for the case without ponding to 9 m for the case with ponding after 50 years of operation, and ponding directly above the pipe induces the maximum thaw depth. Engineering measures should be adopted to control the size or even eliminate surface water-rich ponding for the long-term performance of buried warm-oil pipelines.

  • Comparative studies on leaf epidermal micromorphology and mesophyll structure of Elaeagnus angustifolia L. in two different regions of desert habitat
  • MengMeng Li, YuBing Liu, MeiLing Liu, Dan Liu
  • DOI:10.3724/SP.J.1226.2015.00229
  • 2015, 7 (3): 229–237 Abstract (52) PDF (1449 KB) (88)
  • In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses of Elaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy (SEM), and mesophyll structure was studied by light microscopy (LM) and transmission electron microscopy (TEM). Materials were selected from Linze County, Gansu Province (material A) and Qitai County, Xinjiang Uygur Autonomous Region (material B) of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in material A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stellate-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford resistance to environmental stress.
  • 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 (87) HTML (4) PDF (1767 KB) (87)
  • 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.

  • Comparative foliar anatomy of three Khaya species (Meliaceae) used in Nigeria as antisickling agent
  • Ololade A. Oyedapo,Joseph M. Agbedahunsi,H. C Illoh,Akinwumi J. Akinloye
  • DOI:10.3724/SP.J.1226.2018.00279
  • 2018, 10 (4): 279–285 Abstract (110) HTML (9) PDF (1820 KB) (86)
  • Khaya belongs to the family Meliaceae. In Nigeria the genus is represented by three species viz; K. senegalensis A. Juss., K. grandifoliola C. DC. and K. ivorensis A. Chev. Comparative foliar anatomy of the three Khaya species was carried out to identify and describe distinctive anatomical characters that could possibly be used to delimit the three taxa. Transverse section, epidermal peels and cleared leaves of these three species were made. Characteristic similarity and disparity in the tissues arrangement as well as cell inclusions were noted for description and delimitation. The three Khaya species studied had essentially the same anatomical features, e.g., venation pattern having open polygonal areoles and the veins terminals biforkated. However, there were characters that seem to be species specific, e.g., vien termination number and areole width. The leaf epidermal studies of the three species revealed similarities in stomatal type which are generally staurocytic, epidermal cells and undulating anticlinal cell walls but stomata density varied. Hexacytic stomata is only observed in the abaxial surface of K. grandifoliola which distinguished this species from the others. The leaf petiole shape of the three species are round and difficult to distinguish into adaxial and abaxial surfaces. The cuticle is striated, vascular bundles are heart shape, conjoint, concentric and amphivasal, but are different in epidermal and collenchyma cell layer numbers. The leaf transverse sections of the three Khaya species studied have conjoint, concentric and amphicribral bundles while the leaf cuticle of K. senegalensis and K. grandifoliola are striated but that of Khaya ivorensis is non-striated.

  • Surface-deformation monitoring in the permafrost regions over the Tibetan Plateau, using Sentinel-1 data
  • ZhenMing Wu, Lin Zhao, Lin Liu, Rui Zhu, ZeShen Gao, YongPing Qiao, LiMing Tian, HuaYun Zhou, MeiZhen Xie
  • DOI:10.3724/SP.J.1226.2018.00114
  • 2018, 10 (2): 114–125 Abstract (86) PDF (2925 KB) (85)
  • Differential Interferometric Synthetic Aperture Radar (D-InSAR) has been widely used to measure surface deformation over the Tibetan Plateau. However, the accuracy and applicability of the D-InSAR method are not well estimated due to the lack of in-situ validation. In this paper, we mapped the seasonal and long-term displacement of Tanggula (TGL) and Liangdaohe (LDH) permafrost regions with a stack of Sentinel-1 acquisitions using the Small Baseline Subset InSAR (SBAS-InSAR) method. In the TGL region, with its dry soils and sparse vegetation, the InSAR-derived surface-deformation trend was consistent with ground-based leveling results; long-term changes of the active layer showed a settlement rate of around 1 to 3 mm/a due to the melting of ground ice, indicating a degrading permafrost in this area. Around half of the deformation was picked up on monitoring, in contrast with in-situ measurements in LDH, implying that the D-InSAR method remarkably underestimated the surface-deformation. This phenomenon may be induced by the large soil-water content, high vegetation coverage, or a combination of these two factors in this region. This study demonstrates that surface deformation could be mapped accurately for a specific region with Sentinel-1 C-band data, such as in the TGL region. Moreover, although the D-InSAR technology provides an efficient solution for broad surface-deformation monitoring in permafrost regions, it shows a poor performance in the region with high soil-water content and dense vegetation coverage.
  • Direct shear tests of coarse-grained fillings from high-speed railway subgrade in cold regions
  • QingZhi Wang, JianKun Liu, JianHong Fang, AnHua Xu
  • DOI:10.3724/SP.J.1226.2017.00236
  • 2017, 9 (3): 236–242 Abstract (63) PDF (3277 KB) (85)
  • In order to study the shear behavior of coarse-grained fillings taken from the subgrade bottom layer of a cold region high-speed railway, large scale direct shear tests were conducted with different normal pressures, water contents and temperatures. The results indicate that the relationship between shear displacement and shear stress changed from strain-softening at lower normal pressures to strain-hardening at higher normal pressures, in both unfrozen and frozen states. This phenomenon was mainly due to the shear dilatation deformation effect. The shear displacement-shear stress curves show similar stages. Besides, the shear stress rapidly increased and there was not an increment in the shear displacement during the initial stage of the shear process in the frozen state. In both the unfrozen or frozen states at the same water contents, the shear strength increased with increasing normal pressure.
  • Numerical simulation and experimental validation of moisture-heat coupling for saturated frozen soils
  • ZhiMing Li, Jian Chen, Kai Sun, Bin Zhang
  • DOI:10.3724/SP.J.1226.2017.00250
  • 2017, 9 (3): 250–257 Abstract (88) PDF (1039 KB) (85)
  • In seasonally frozen regions, freezing-and-thawing action is the main cause responsible for the destruction of canals, which is closely linked to the temperature gradient and water transport. To investigate the behaviour of soils under freezing-and-thawing actions, many numerical models have been established that consider the important coupling of moisture transport and temperature evolution; but they contain excessive parameters, some of which are rather difficult to determine. Based on the well-known Harlan's theory, a simple moisture-heat coupling model was recently proposed to quantify the coupled moisture-heat transport performance of soils in terms of the central temperature and porosity. The mathematical module of COMSOL Multiphysics was further employed to solve the governing equations numerically. To validate our model, a thorough experimental scheme was carried out in our lab. The measured temperature distribution was found to be consistent with the predicted results.
  • Soil hydraulic conductivity and its influence on soil moisture simulations in the source region of the Yellow River―take Maqu as an example
  • DongYu Jia,Jun Wen,Xin Wang,ZuoLiang Wang
  • DOI:10.3724/SP.J.1226.2019.00360.
  • 2019, 11 (5): 360–370 Abstract (78) HTML (7) PDF (2177 KB) (85)
  • aturated hydraulic conductivity and unsaturated hydraulic conductivity which are influenced by soil are two important factors that affect soil water transport. In this paper, data supplied by the Chinese Academy of Sciences are used to determine true unsaturated hydrology values. Furthermore, in combination with observed, model simulation and experimental data, an improved saturated hydraulic conductivity parameterization scheme is carried out in CLM4.5 at a single point in the summer. The main results show that: (1) After improving saturated hydraulic conductivity in CLM4.5 through a parameterization modification, it is found that shallow layer soil moisture increases compared to the initial value; and (2) The numerical values of unsaturated hydraulic conductivities in the model are obviously larger than experimental values. By substituting the Brooks-Corey soil water characteristic curve into the Mualem model, the value of unsaturated hydraulic conductivity is modified; (3) By using the modified value, it is found that the attenuating magnitude of simulated soil moisture caused by each rainfall event is reduced. The soil moisture variation in shallow layers (5, 10 and 20 cm) could be better displayed.

  • 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 (71) PDF (2066 KB) (84)
  • 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.
  • Characterization of landscape pattern based on land economic niche change: A case study in Ganzhou, Gansu Province, China
  • HuaLi Tong, PeiJi Shi, XueBin Zhang, ZaiYan Li
  • DOI:10.3724/SP.J.1226.2018.00261
  • 2018, 10 (3): 261–270 Abstract (53) PDF (1614 KB) (82)
  • Land use change has a profound impact on biodiversity and ecological processes, and is closely related to changes in landscape patterns. This paper introduces the theory and method of land economic niche into landscape ecology, which provides a new method for spatial characterization of urban and rural spatial landscape patterns. Based on this theory, this paper analyzes the landscape pattern of Ganzhou District by using Landsat images as data source in 1995, 2000, 2005, 2010 and 2015. We calculated the land economic niche by applying the niche potential theory. Combined with the theory of landscape ecology, we explored the effects of the land economic niche change on the landscape pattern at a county scale. The results show that economic niche of construction land, watershed and farmland increased during 1995-2015, and grassland declined significantly. The economic niche of farmland, construction land, watershed and grassland show a negative correlation with the number of patches (NP), fragmentation index (FN) and the fractal dimension index (FD), and had a positive correlation with the aggregation index (AI). There was no significant correlation between the forest land economic niche and landscape metrics. The change of land economic niche has a driving effect on the landscape pattern of the county, which can represent the economic development direction of Ganzhou District. The land economic niche is closely related to the landscape type which can directly obtain an economic benefit.