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15 May 2018, Volume 35 Issue 3 Previous Issue    Next Issue

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Analysis of Characteristics of Soil Salinity in the Oasis of Arid Area WANG Qiao-huan, LU Yu-dong, SAI Jia-mei, LI Huan-huan 2018, 35 (3):  503-509.  doi: 10.13866/j.azr.2018.03.01 Abstract ( 537 )   PDF (1409KB) ( 613 )     The study area is located in the Yaoba oasis irrigated area in the Alxa League of Inner Mongolia. Based on the field investigation, soil samples collection and indoor experiment analysis, using descriptive statistical method, correlation analysis method, principal component analysis (PCA) method, this article analyzed the distribution characteristics of surface soil total salt and salt ions in Yaoba oasis. According to descriptive statistical analysis, the results showed that surface soil of Yaoba oasis was alkaline chlorine-sulfate soil salinization. The cations accumulation of surface soil were dominated by salt ions of Ca2+,K++Na+ and the anion accumulation of surface soil was dominated by salt ion of HCO3-.The distribution characteristics of soil total salt presented high values in the southwest and low values in the northeast. Soil total salt varied largely from east to west and varied small from south to north. In surface soil, the salt ions of HCO3-, K++ Na +, SO42- and Cl- presented strong variability; soil total salt, salt ions of Ca2+, Mg2+ and HCO3- presented moderate variability; pH presented weak variability. Through correlation analysis, it showed that soil total salt had the significant positive correlation with soil salt ions of SO42-,Ca2+,K++Na+,Cl-,Mg2+andthe highest correlation coefficient was 0.958 with ion of SO42-; but pH had the significant negative correlation with soil salt ions of Mg2+,Ca2+,Cl-,SO42- and all correlation coefficients were less than 0.6. According to principal component analysis(PCA) , it showed that there were two principal component factors which could present the characteristics of surface soil salt in study area. One principal component factor presented soil salt component and another principal component factor presented alkalinity, so it concluded that salt ions of SO42-, K++Na+, Ca2+,Cl- were the key characteristics factors of soil salinization. At the end, this study established the equations of principal component comprehensive score. According to comprehensive score calculation of 42 soil samples, the value range was 3.6~10.7, the average value was 5, the standard deviation was 1.5, so the comprehensive score presented moderate variability. The study results will provide theory and practical basis for prevention and control soil salinization and can make sure security development of agriculture and animal husbandry in study area. References | Related Articles | Metrics

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Spatial Variation of Soil Organic Carbon Content and Its Driving Factors along South-North transect in the Loess Plateau of China Ren Guang-qi, Jia Xiao-xu, Jia Yu-hua,Guo Cheng-jiu 2018, 35 (3):  524-531.  doi: 10.13866/j.azr.2018.03.04 Abstract ( 668 )   PDF (1280KB) ( 573 )    The China’s Loess Plateau is characterized by severe water shortage, thick loess deposits and intensive soil erosion, and it is a typical ecological fragile region in China and even around the world. Serious soil erosion and long-term irrational land reclamation in this region leads to a decline of soil organic carbon content (SOC). As an important component in the terrestrial ecosystem, the SOC which is closely related to soil physical, chemical and biological properties is a key factor affecting soil fertility and productivity of ecosystem. Slight fluctuation of soil organic carbon pool, which is caused by the changes of land use, land management measures or soil erosion rate, affects strongly the carbon dioxide in atmosphere and thus the global climate change. The spatial distribution of SOC has generally a high heterogeneity due to the influence of climate (i.e. temperature and precipitation), soil texture, soil type, vegetation type, terrain conditions (such as elevation, slope aspect and slope gradient) and land use type. However, the SOC was focused on mainly on the small spatial scales (generally < 2 km2) in previous studies, which is insuf?cient for understanding the spatial characteristics of SOC on regional and/or global scale. Besides, the available researches overlooked the amount and spatial pattern of SOC in deeper soil layers (deeper than 1 m), which failed to provide a reliable evidence for precise regional soil carbon stock evaluation. In this study, an 860 km south-north transect was designed, and the values of SOC at 500 cm depth were measured at an interval of 10 km (n= 86) along the transect. Thus, the objectives of the study were to investigate the spatial variation of SOC on regional scale and to derive the primary factors dominating the spatial distribution of SOC in different soil layers by using the classical statistics and geostatistics. The results showed that the mean SOC of the 0-500 cm soil profile decreased generally from the south to the north of the plateau along the horizontal direction. Along the vertical direction, SOC decreased gradually with the increase of soil depth above 100-cm soil layer, while it tended to be stable in the 100-500 cm layer. Under different land use types, SOC was generally in an order of cropland (5.79 g·kg-1) > forestland (3.34 g·kg-1) > grassland (2.20 g·kg-1). A moderate variation of SOC occurred in various soil layers along a 0-500 cm profile, and the best fitting semivariogram models for SOC in the 0-150 cm and 150-500 cm soil layers were Gaussian and Exponential. The controlling factors of SOC were different from different soil layers: SOC in the top 40 cm soil layer was mainly influenced by mean annual precipitation and slope gradient, while that in the 40-500 cm soil layer was controlled by soil texture, mean annual precipitation and temperature. Results suggested that the regional distribution of SOC in shallow soil layers (< 40 cm in depth) was determined by climate and topographic conditions, while that in deep soil layers (40-500 cm in depth) tended to be determined by soil texture and climate. The results could provide a scientific basis for ecological regeneration and regional soil carbon stock evaluation. References | Related Articles | Metrics

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Applicability of ITPCAS and CMORPH Precipitation Datasets over Shaanxi Province WANG Yu-dan, CHEN Hao, LIU Canran, DING Yong-jian 2018, 35 (3):  579-588.  doi: 10.13866/j.azr.2018.03.10 Abstract ( 620 )   PDF (2534KB) ( 421 )    Compared with the precipitation data from meteorological stations, the precipitation products based on remote sensing can be used to well present the spatial distribution of precipitation, whereas the accuracy of remote sensing products generally cannot match that of the meteorological stations. Thus it is necessary to evaluate the common used precipitation products are. In this paper, the reliability of two satellites precipitation products ITPCAS and CMORPH with high spatial-temporal resolution over Shaanxi Province was evaluated using the observed data from 36 national and 23 regional meteorological stations. Analysis based on the indexes including the detection rate of precipitation events, capture rate over all precipitation magnitudes and errors of precipitation at different spatial-temporal scales was adopted in the evaluation. Results showed that the ITPCAS was accurate for the Shaanxi region because of its low bias of average daily precipitation, low false alarming ratio and missed ratio, high capture rate of precipitation for grades higher than moderate magnitude, good presentation of the distribution and variation pattern of the precipitation. The spatial distribution and change pattern of precipitation in the Shaanxi region could well present by ITPCAS precipitation. CMORPH also showed the spatial distribution pattern of precipitation in the Shaanxi region. However, the errors were comparatively higher as CMORPH did not merge any data from meteorological stations. Further revisions of the CMORPH are needed to ensure the accuracy of the products. References | Related Articles | Metrics

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Uncertainty of Evapotranspiration Products Based on Fusion of Multi-source Remote Sensing Data and Land Surface Modes in Xinjiang CUI Jun-jie, BAI Jie, ZHENG Lei, LI Yu-zhen, ZHAO Hong-fei, YUAN Xiu-liang, LI Long-hui 2018, 35 (3):  597-605.  doi: 10.13866/j.azr.2018.03.12 Abstract ( 708 )   PDF (1722KB) ( 689 )   Evapotranspiration (ET) is an indispensable part of water resources consumption in arid region, and it is also one of the key indicators used for assessing water resources. As the vegetation here is extremely sparse and has relatively high spatial heterogeneity, it is a challenge to accurately estimate ET in arid region. Most of the common ET products based on fusion of multi-source remote sensing data and land surface modes showed the different ET results in arid region. The results of different ET products with eddy covariance (EC) measurements were generally compared in previous studies, but the issues of spatial scale mismatch between EC data and ET products are unresolved yet. It is difficult to obtain the true values of ET in large scale. The sources of uncertainty may be from the different model structures, calculation methods, forcing datasets, and so on. In this paper, three Cornered Hat (TCH) methods without requiring a priori knowledge of the observed ET values were used to estimate the uncertainties of ET output in Xinjiang based on the Common Land Model (CoLM), Global Land Evapotranspiration Amsterdam Model (GLEAM) and Moderate Resolution Imaging Spectroradiometer ET products (MOD16). The results showed that the spatial patterns of GLEAM and MOD16 ET products were similar, and the ET values in the mountains were significantly higher than that in the plains. The ET values of CoLM in the Altay and Tianshan mountains were significantly higher than that in the plains. In addition, the mean annual ET values in Xinjiang during the period from 2000 to 2014 differed markedly, and they were 142.36±11.11 mm·a-1, 126.66±19.12 mm•a-1 and 78.64±4.61 mm·a-1 obtained by the GLEAM, CoLM and MOD16 respectively. The CoLM and MOD16 products revealed that there was no significant decrease trend in ET during the period from 2000 to 2014 (-1.03 mm•a-1 and -0.24 mm•a-1 respectively, P> 0.05). The GLEAM product showed that there was no significant increase trend in ET (0.02 mm·a-1, P> 0.05). The uncertainty based on the TCH method of CoLM was the highest (24.18 mm•a-1) in Xinjiang, that based on the GLEAM was moderate (21.58 mm•a-1), and that based on the MOD16 was the lowest (17.66 mm•a-1). In the shrub lands, Tianshan Mountains and semi-humid region, the uncertainties of CoLM (33.47, 30.46 and 32.11 mm/a) were significantly higher than those of GLEAM (28.31, 24.73 mm•a-1 and 24.19 mm·a-1) and of MOD16 (9.50, 14.80 mm•a-1 and 14.34 mm•a-1). It was crucial to quantify the uncertainty of regional ET based on the CoLM, GLEAM and MOD16 ET products for accurately estimating water consumption and providing appropriate ET product for long-term water cycle change in Xinjiang. The method used in this paper might provide a reference for analyzing the uncertainty. References | Related Articles | Metrics

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Spatiotemporal Variation of Vegetation Cover in the Pastoral Area in Northwestern China during the Period of 1981-2015 MOU Le, LU Yi-xiao, YANG Hui-min, FENG Qi-sheng 2018, 35 (3):  615-623.  doi: 10.13866/j.azr.2018.03.14 Abstract ( 748 )   PDF (3645KB) ( 724 )   he major parts of pastoral area in northwest China are generally the arid and semiarid regions, and the vegetation in this area is extremely sensitive to environmental change and susceptible to human activities. In recent years, the vegetation in the arid pastoral area is changed obviously, which is affected by the production of agriculture and animal husbandry and the ecological construction. Therefore, it is vital to further understand the vegetation variation in the pastoral area in northwest China, where the national ecological projects and planting structure adjustment of agriculture are implemented, and the theoretical supports are provided for the production of agriculture and animal husbandry and the ecological construction. In this study, the GIMMS 3g NDVI product with a spatial resolution of 8 km × 8 km during the period from 1981 to 2015 was used to reveal the spatiotemporal characteristics of vegetation change in the study area with the Theil-Sen Median trend analysis, Mann-Kendall test and Hurst index. The results showed that the typical vegetation in the arid pastoral area was changed significantly during the period from 1981 to 2015, and the improved area accounted for 41.9% of the total area. The improvement of vegetation was the most obvious from 2006 to 2015, and the improved area occupied 63.7% of the total. All the 11 vegetation types were in a regenerating trend, in which the largest share came from cultivated vegetation, the improved area occupied more than 80% of the total, and the improved areas of pasture and hassock were over 60%. In the past 35 years, the vegetation coverage in the arid pastoral area was tended to a sustainable and positive development, and the proportion of continuously regenerating area was higher than 70% of the total. During the period of 2006-2015, the regeneration and stability occurred in 63.8% of the total area. National ecological projects and planting structure adjustment of agriculture affect significantly the vegetation cover in the arid pastoral areas in northwest China. In the future, the vegetation coverage is supposed to be continuously restored. References | Related Articles | Metrics

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Effects of Snow Cover and Arbuscular Mycorrhizal Fungi Network on the Seedling Growth of Erodium oxyrrhynchum WU Nan, ZHANG Jing, WANG Yue, YIN Jin-fei, ZHANG Yuan-ming 2018, 35 (3):  624-632.  doi: 10.13866/j.azr.2018.03.15 Abstract ( 585 )   PDF (1294KB) ( 528 )    Compared to other desert ecosystem, snow cover in winter in the Gurbantunggut Desert is relatively stable and thick. Moisturizing and warming effects of snow cover provide the good conditions for the growth of desert ephemeral plants. However, the desert ephemeral plants can make use of favorable conditions in early spring of two months to complete the whole process of their rapid growth. They have an important role in the formation and succession of plant community as well as sand-fixation. The well-developed herbaceous layer in the Gurbantunggut Desert is mainly related to the existence of stable snow cover in winter. A comprehensive understanding that the ephemeral plant-arbuscular mycorrhizal fungi (AMF) how to respond to the changes of snowfall and snow cover in winter is the key to reveal the stability and maintenance mechanism of desert ecosystem under the climatic and environmental changes. However, it is not clear whether there is an interaction between AM fungi and snow cover change, and how about the growth and reproductive characteristics of ephemeral plants response to the interaction. Erodium oxyrrhynchum is a typical dominant desert ephemeral plant species growing in deserts in the Junggar Basin in north Xinjiang. Our research was carried out at the ecosystem in the Gurbantunggut Desert on the basis of long-term monitoring of plots. A dual influence of physical factor (snow cover) and biological factor (AMF) on the seedling growth of dominant desert ephemeral plants was verified based on the altered treatments of field snow cover (snow cover removal, snow cover addition and natural snow cover left in place), on-site mycorrhizal treatments (PVC tube rotated and static) and analysis in laboratory. A dual influence of snow cover removal-PVC rotated treatment on the seedling growth of E. oxyrrhynchum was detected. The results are as follows: ① In non-mycorrhizal treatment (rotated PVC tubes), the leaf traits of E. oxyrrhynchum were lower than that under the mycorrhizal treatment (static PVC tubes). The snow cover removal (-S) treatment exacerbated the above difference. Compared to the snow cover addition (+S) treatment, the leaf area and leaf perimeter under the –S treatment were reduced by 70.92% and 37.26% respectively; ② Other surveys echoed the conclusions that the non-mycorrhizal treatment restricted the plant growth. In non-mycorrhizal treatment, the plant height and root length of E. oxyrrhynchum were also lower than that under the mycorrhizal treatments. Plant height was decreased by 40.45% under the (+S) treatment and by 39.47% under the (-S) treatment. Root length was also decreased by 47.75% under the (-S) treatment; ③ The non-mycorrhizal treatment was also suggested to impede the biomass accumulation. In non-mycorrhizal treatment, both aboveground and underground biomasses were lower than that under mycorrhizal treatments. The snow cover removal (-S) treatment exacerbated the above difference. Under the –S treatment, the aboveground and underground biomasses were decreased by 80.32% and 65.74% respectively. In conclusion, the dual ecological influence of non-mycorrhizal treatment and –S treatment was found to impede the seedling growth of desert ephemeral plants of E. oxyrrhynchum. Our results could provide the scientific data for speculating the adaptation mechanism of desert ephemeral plants under winter precipitation change. References | Related Articles | Metrics

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Land Use Change in the Three-River Headwaters in Recent 40 Years 2018, 35 (3):  695-704.  doi: 10.13866/j.azr.2018.03.24 Abstract ( 646 )   PDF (2407KB) ( 949 )   In this study, the Arcgis10.0 spatial statistical analysis and the qualitative and quantitative methods were used to analyze the spatial distribution, dynamic change and future trend of land use/cover change in the three-river headwaters based on the 1: 100000 land use dataset from 1980 to 2015. The purposes of the study were to solve the problems of degeneration of grasslands, soil erosion and environment deterioration in the study area. The results are as follows:(1) Land use change was significant during the whole research period. The main land use change was divided into three periods: a degeneration of grasslands occurred during the first 15-year period (1980-1955), the land use change was slow during the second 15-year one (1995-2000), and the degenerated grasslands were regenerated during the last 15-year one (2000-2015); (2) During the period from 1980 to 2015, the areas of grasslands with low and high coverage, waters and construction land were enlarged in a fluctuation way, the area of unused land (sandy land, saline land, swamp, etc.) was reduced significantly, the areas of grasslands with moderate coverage and woodlands were basically unchanged, and the total area of grasslands was enlarged by 13.45% and mainly from the reduction of unused land; (3) The land use change was mainly caused by the conversion among grasslands, unused land and waters; (4)The CA- Markov model was used to predict that the total area of waters would be unchanged, the areas of grasslands with high and low coverage, unused land, cultivated land and construction land would be continuously enlarged, but the area of woodland would be reduced; (5)The change of population, economic structure and policy were the main reasons affecting land use change, and the supply-demand balance of ecological assets was the driving factor of land use/cover change. Therefore, it was proposed to strengthen the basic cultural construction, conserve the natural grasslands and optimize the land use and production modes so as to promote the sustainable development in the study area. References | Related Articles | Metrics

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Effects of Climate Change on Grain Production in Plain Oasis in the Yarkant River Basin ZHANG Xue-qi, Mansur Sha-biti, MA Guo-fei 2018, 35 (3):  705-712.  doi: 10.13866/j.azr.2018.03.25 Abstract ( 510 )   PDF (2357KB) ( 492 )   In order to analyze the grain production situation in the study area and its response to climate change, the meteorological and agricultural data were used to analyze the climate change in recent 60 years and its effect on agricultural climate resources, sown area and per unit area yield with the linear trend, cumulative anomaly and mutation method, and a multiple linear regression equation was developed to predict the future changes in grain yield for guiding scientific farming and better serving the agricultural ecosystem. The results are as follows: ① Over the past 60 years, an obvious warming-wetting trend occurred in the study area. The temperature and precipitation increase rates were 0.2℃·（10a）-1(P<0.01) and 4.5 mm·（10a）-1(P< 0.05) respectively, but the sunshine duration decreased with a decrease rate of 21.1 h·（10a）-1. The temperature mutation occurred in 1996, but there were no obvious mutations in precipitation and sunshine duration; ②With climate warming, the duration of cumulative temperature ≥10 ℃ increased by 19d, but that of negative one shortened by 8 d; ③ In addition to the negative cumulative temperature, the grain yield was positively correlated with air temperature, sunshine duration, cumulative temperature ≥10 ℃, sown area, per unit area yield and applying quantity of chemical fertilizer; ④ The multiple regression model revealed that 7 independent variable factors could be used to explain the 99.7% grain yield variation without considering other factors. Climate change is conducive to expanding grain sown area and increasing per unit area yield to a certain extent. References | Related Articles | Metrics

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Morphologic Features and Forming Causes of Plant Sandpiles in Alpine Sand Land ZHANG Deng-shan, TIAN Li-hui, ZHANG Ming-yuan, ZHOU Xin 2018, 35 (3):  713-721.  doi: 10.13866/j.azr.2018.03.26 Abstract ( 521 )   PDF (2527KB) ( 630 )   Morphology of plant sandpiles is an important reflection of ecological suitability and sand-fixing benefits of different artificial plants. Based on the explorations of the features and formation causes of sandpiles, the erosion and deposition of plant sandpiles can be instinctively compared to provide some basic reasons for selecting the sand-fixing plant species. It is also vital to reveal the relationship between alpine vegetation growth and wind-blown sand activities. The main sandpiles where five typical sand-fixing plant species were afforested in the Ketu sand land on the eastern shore of Qinghai Lake were focused on. Based on the methods of morphological fitting and sand-deposition monitoring, three-dimensional morphology of vegetation sandpiles was simulated and analyzed with the vegetation investigations and wind-blown sand observations during the period of 2015-2016. Based on the statistic results of the total and sectional deposition depths, intensity and affecting factors of wind-blown sand, we found that: ① The sandpiles with conical, hemispherical or linear shapes could form if Hippophae rhamnoides, Salix cheilophila, Pinus sylvestris, Simon poplar and Artemisia desertorum were afforested. Deep and strong sand deposition could occur on the H. rhamnoides and A. desertorum sandpiles, and the projected area and three-dimensional volume of these sandpiles were larger than those of other three light-erosive or light-depositional plant sandpiles; ② Among the eight directional sections of the sandpiles, sand deposition occurred mainly along the northeast-east-southeast directions. In consequence of significant negative correlations between depositional intensity and sediment transport rate along the same directions, the depositional intensity and direction over all the vegetation sandpiles were quite different, especially over the S. cheilophila, S. poplar and A. desertorum sandpiles. In addition, the deposition depth and intensity changed significantly along the directions of northwest, east and southeast; ③ The morphologic differences of plant sandpiles were mainly affected by vegetation growth, the sand depositional depth of H. rhamnoides and S. poplar sandpiles increased with the increase of plant height and canopy and soil crust, especially with their coupling effects. P. sylvestris and S. poplar sandpiles were strongly affected by the basal diameter and clear bole length. Furthermore, the strong west-northwest-north winter wind affected the sandpile erosion, it was also verified by the significantly negative correlations between the directional sand accumulated depth and sand transport intensity, especially for the S. cheilophila and A. desertorum. Calculated by the sand-fixing intensity and surface sediment transport intensity, we could predict the sand accumulation modulus of the five forest dunes, the H. rhamnoides and S. cheilophila forests prevented the sand most with the amount of 400-1 100 t·hm2. because of their high afforesting density and surviving rates. In general, H. rhamnoides, S. cheilophila and A. desertorum could be chosen as the adaptive and efficient sand-fixing vegetation species with sand-fixing benefits of 40.45%, 15.53 % and 62.72% respectively, while the other artificial plant species demand afforesting conservation and structure optimization for their low sand-prevention effects lower than 5%. References | Related Articles | Metrics

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Correlation between the Stable Carbon Isotopes in Annual Layers of Tamarix ramosissima Sand-hillocks in the Lower Reaches of the Tarim River LIU Bo, LIU Hong-ling,MU Yu-di, LI Gui-fang, HE Ya-ling, ZHUANG Li 2018, 35 (3):  735-742.  doi: 10.13866/j.azr.2018.03.28 Abstract ( 646 )   PDF (1314KB) ( 427 )   The Tarim River is located in the north of the Taklimakan Desert in Xinjiang Uygur Autonomous Region, China. The recession of groundwater level and concomitant increase of soil salinity have reduced vegetation coverage in the lower reaches of the river. Tamarix ramosissima is one of the dominant plant species in the riparian ecosystem. With the continuous growth of T. ramosissima shrubberies, sand is blocked by the formation of Tamarixia sand, the T. ramosissima sand-hillocks with unique hierarchical structure form ultimately after a long-term interaction of sand and T. ramosissima shrubberies. T. ramosissima sand-hillocks are rich in environmental information. The sand thickness, grain size and mineral composition of the T. ramosissima sand-hillocks were analyzed. Three observation sections of Yingisu, Abdullah and Karda in the lower reaches of the Tarim River were designed to study the relationship between δ13C and carbon content in annual layers of T. ramosissima sand-hillocks and that between the morphological characteristics of T. ramosissima shrubberies and the morphological changes of T. ramosissima sand-hillocks. The results are as follows: (1) The content of δ13C in the litters of T. ramosissima was gradually decreased with the increase of annual layers of T. ramosissima sand-hillocks, and there was a negative correlation between δ13C value and carbon content. The average value of δ13C of the measured samples was -24.42 ‰, the maximum and the minimum were -22.09‰ and -25.24‰ respectively; (2) As the annual layers of T. ramosissima sand-hillocks increased, the δ13C value of the T. ramosissima shrubberies was reduced year by year, and the long axis and short axis, height and spatial occupancy of T. ramosissima shrubberies and the height, length, width and spatial share of the T. ramosissima sand-hillocks were all in an increase trend; (3)There were the good correlations among the morphological parameters of the T. ramosissima shrubberies and of the T. ramosissima sand-hillocks, in which the correlations among the annual layers and the T. ramosissima shrubberies and sand-hillocks were significant, and these revealed that there was a mutual feedback effect between the promotion of the T. ramosissima sand-hillocks to the growth of T. ramosissima shrubberies and the δ13C value of the T. ramosissima shrubberies. References | Related Articles | Metrics