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Vegetation cover change and the driving factors over northwest China
ShengPei DAI, Bo ZHANG, HaiJun WANG, YaMin WANG, LingXia GUO, XingMei WANG, Dan LI
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00025
Abstract6648)      PDF (468KB)(4558)      
In this paper the spatio-temporal variation of vegetation cover in northwest China during the period of 1982-2006 and its driving factors were analyzed using GIMMS/NDVI data. The annual average NDVI was increased with a rate of 0.0005/a in northwest China and there was an obvious difference between regions. The trend line slopes of NDVI were higher than 0.0005 in the Tianshan Moutains and Altay Mountains of Xinjiang, the Qilian Mountains of Gansu and the eastern part of Qinghai, which indicated the vegetation cover was significantly increased in these areas. The trend line slopes of NDVI were lower than -0.0005 in the southern region of Qinghai, the border regions of Shaanxi and Ningxia, the parts of Gansu and Tarim Basin, Turpan and Tuoli in Xinjiang, which indicated the vegetation cover was declined in these areas. The NDVI of woodland, grassland and cultivated land had an ascending tendency during the study period. The study shows that the vegetation cover change was caused by both natural factors and human activities in northwest China. The natural vegetation change, such as forests was influenced by climate change, while human activities were the main reason to the change of planting vegetation. The changes of vegetation covers for different elevations, slopes and slope aspects were quite different. When the elevation is exceeded to 4,000 m, the NDVI increasing trend was very low; the NDVI at the slope of less than 25° was increased by the ecological construction; the variation of NDVI on sunny slope was stronger than that on shady slope. The temperature rose significantly in recent 25 years in northwest China by an average rate of 0.67oC/10a, and precipitation increased by an average rate of 8.15 mm/10a after 1986. There was positive correlation between vegetation cover and temperature and annual precipitation changes. Rising temperature increased the evaporation and drought of soils, which is not conducive to plant growth, and the irrigation in agricultural areas reduced the correlation between agricultural vegetation NDVI and precipitation. The improvement of agricultural production level and the projects of ecological construction are very important causes for the NDVI increase in northwest China, and the ecological effect of large-scale ecological construction projects has appeared.
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Spatial distribution of vegetation and the influencing factors in Qaidam Basin based on NDVI
WenBin ZHU, AiFeng LV, ShaoFeng JIA
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00085
Abstract5988)      PDF (377KB)(6142)      
The spatial distribution of vegetation in Qaidam Basin was analyzed using GIMMS (Global Inventory Modeling and Mapping Studies) / NDVI (Normalized Difference Vegetation Index) data set from January 1982 to December 2006. Based on the data of precipitation, terrain, stream systems, land use and the map of vegetation distribution in Qaidam Basin, we studied the factors influencing the spatial distribution of vegetation. The results showed that the vegetation was generally low in Qaidam Basin and there was a clear semi-ring structure from southeast to northwest. In some areas, the existence of rivers, lakes and spring belts turned this semi-ring structure into a non-continuous state and formed distinct bright spots and continuous linear features. There were four main factors that affected the spatial distribution of vegetation coverage in Qaidam Basin, i.e., precipitation, hydrological conditions, altitude and human activities. Precipitation and altitude have a correlation and determine the basic pattern of vegetation distribution in Qaidam Basin. The impacts of hydrological conditions and human activities were mainly embodied in partial areas, and often broke the pattern of vegetation distribution dominated by precipitation and altitude.
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Spatio-temporal pattern and changes of evapotranspiration in arid Central Asia and Xinjiang of China
Xi CHEN, BaiLian LI, Qin LI, JunLi LI, Saparnov ABDULLA
Journal of Arid Land    2012, 4 (1): 105-112.   DOI: 10.3724/SP.J.1227.2012.00105
Abstract4482)      PDF (8278KB)(4053)      
Accurate inversion of land surface evapotranspiration (ET) in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response of water resources. It is also important in the functional evaluation of regional water cycle and water balance, as well as the rational allocation and management of water resources. This study, based on model validation analysis at varied scales in five Central Asian countries and China’s Xinjiang, developed an appropriate approach for ET inversion in arid lands. The actual ET during growing seasons of the study area was defined, and the changes in water participating in evaporation in regional water cycle were then educed. The results show the simulation error of SEBS (Surface Energy Balance System) model under cloud amount consideration was 1.34% at 30-m spatial scale, 2.75% at 1-km spatial scale and 6.37% at 4-km spatial scale. ET inversion for 1980–2007 applying SEBS model in the study area indicates: (1) the evaporation depth (May–September) by land types descends in the order of waters (660.24 mm) > cultivated land (464.66 mm) > woodland (388.44 mm) > urbanized land (168.16 mm) > grassland (160.48 mm) > unused land (83.08 mm); and (2) ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68×108 m3 (with an evaporation/precipitation ratio of 1.05) and 9,741.03×108 m3 (with an evaporation/precipitation ratio of 1.4), respectively. The results unveiled the spatio-temporal variation rules of ET process in arid areas, providing a reference for further research on the water cycle and water balance in similar arid regions.
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Impacts of livestock grazing on a savanna grassland in Kenya
John KIOKO, John Warui KIRINGE, Simon Ole SENO
Journal of Arid Land    2012, 4 (1): 29-35.   DOI: 10.3724/SP.J.1227.2012.00029
Abstract4319)      PDF (662KB)(7707)      
The dynamics of most rangelands in Kenya remain to be poorly understood. This paper provides baseline information on the response of a semiarid rangeland under different livestock grazing regimes on land inhabited by the Massai people in the east side of Amboseli National Park in Kenya. The data were collected from grasslands designated into four types: (1) grassland from previous Massai settlements that had been abandoned for over twenty years; (2) grassland excluded from livestock grazing for eight years; (3) a dry season grazing area; and (4) a continuous grazing area where grazing occurred throughout all seasons. Collected data included grass species composition, grass height, inter-tuft distance, standing grass biomass and soil characteristics. The results indicated that continuous grazing area in semiarid rangelands exhibited loss of vegetation with negative, long-term effects on grass functional qualities and forage production, whereas grassland that used traditional Maasai grazing methods showed efficiency and desirable effects on the rangelands. The results also showed that abandoned homestead sites, though degraded, were important nutrient reservoirs.
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Transdisciplinary research for supporting the integration of ecosystem services into land and water management in the Tarim River Basin, Xinjiang, China
Tuck-Fatt SIEW, Petra DoLL
Journal of Arid Land    2012, 4 (2): 196-210.   DOI: 10.3724/SP.J.1227.2012.00196
Abstract4054)      PDF (230KB)(3208)      
There is a growing need for both science and practice domains to collaboratively and systematically seek knowledge-based strategies for sustainable development. In recent years, transdisciplinary research has emerged as a new approach that enables joint problem solving among scientists and stakeholders in various fields. In this paper, we aim to introduce transdisciplinary research for supporting the integration of the concept of ecosystem services into land and water management in the Tarim River Basin, Xinjiang, Northwest China. While a large number of ecosystem service studies have helped to raise the awareness for the value of nature in China, a number of challenges remain, including an improved understanding of the relationships between ecosystem structure, functions and services, and the interaction of the various ecosystem services. A meaningful valuation of ecosystem services also requires the consideration of their strong spatial heterogeneity. In addition, ways to introduce the concept of ecosystem services into decision-making in China need to be explored. Thus, successful integration of the concept of ecosystem services into actual land and water management requires a broad knowledge base that only a number of scientific disciplines and stakeholders can provide jointly, via a transdisciplinary research process. We regard transdisciplinary research as a recursive process to support adaptive management that includes joint knowledge generation and integration among scientists and stakeholders. System, target, and transformation knowledge are generated and integrated during the process of (1) problem (re)definition, (2) problem analysis and strategy development, and (3) evaluation of the impact of the derived strategy. Methods to support transdisciplinary research comprise participatory modelling (actor-based modelling and Bayesian Networks modelling) and partici-patory scenario development. Actor-based modelling is a semi-quantitative method that is based on the analysis of problem perspectives of individual stakeholders as depicted in perception graphs. With Bayesian Networks, complex problem fields are modelled probabilistically in a simplified manner, using both quantitative data and qualitative expert judgments. These participatory methods serve to integrate diverse scientific and stakeholder knowledge and to support the generation of actually implementable management strategies for sustainable development. For the purpose of integrating ecosystem services in land and water management in the Tarim River Basin through trans-disciplinary research, collaboration among scientists and institutional stakeholders from different sectors including water, agriculture, forestry, and nature conservation is required. The challenge is to adapt methods of transdisciplinary research to socio-cultural conditions in China, particularly regarding ways of communication and decision-making.
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Rare and endangered plant species of the Chinese Altai Mountains
Marina V. OLONOVA, DaoYuan ZHANG, ShiMing DUAN, LinKe YIN, BoRong PAN
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00222
Abstract4051)      PDF (442KB)(4732)      
Altai (also named Altay in China) Mountain Country (Mountain System) is a unique natural region, located on the border between different floristic regimes of the Boreal and ancient Mediterranean sub-kingdoms, where distribution of plant species is actually limited. It is known to have sufficient endemic floral biodiversity in the Northern Asia. Many plants of Altai Mountain System need effective care and proper conservation measures for their survival and longer-term protection. Important Plant Area identified as the IUCN (the International Union for Conservation of Nature), specified criteria attract global attention for protection of floral biodiversity across the world. The records of 71 plant species from the Chinese Altai Mountains attributed to the criterion A and the dark conifer forests of Chinese Altai Mountains satisfied the criterion C, which may help qualify to fulfill the national obligation of the Convention on Biological Diversity.
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Retrieval of leaf biochemical properties by inversed PROSPECT model and hyperspectral indices: an application to Populus euphratica polymorphic leaves
ZhongGuo MA, Xi CHEN, Quan WANG, PingHeng LI, Guli Jiapaer
Journal of Arid Land    2012, 4 (1): 52-62.   DOI: 10.3724/SP.J.1227.2012.00052
Abstract4005)      PDF (1122KB)(3368)      
Leaf biochemical properties have been widely assessed using hyperspectral reflectance information by inversion of PROSPECT model or by using hyperspectral indices, but few studies have focused on arid ecosystems. As a dominant species of riparian ecosystems in arid lands, Populus euphratica Oliv. is an unusual tree species with polymorphic leaves along the vertical profile of canopy corresponding to different growth stages. In this study, we evaluated both the inversed PROSPECT model and hyperspectral indices for estimating biochemical properties of P. euphratica leaves. Both the shapes and biochemical properties of P. euphratica leaves were found to change with the heights from ground surface. The results indicated that the model inversion calibrated for each leaf shape performed much better than the model calibrated for all leaf shapes, and also better than hyperspectral indices. Similar results were obtained for estimations of equivalent water thickness (EWT) and leaf mass per area (LMA). Hyperspectral indices identified in this study for estimating these leaf properties had root mean square error (RMSE) and R2 values between those obtained with the two calibration strategies using the inversed PROSPECT model. Hence, the inversed PROSPECT model can be applied to estimate leaf biochemical properties in arid ecosystems, but the calibration to the model requires special attention.
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Dynamics of arbuscular mycorrhizal fungi associated with desert ephemeral plants in Gurbantunggut Desert
Tao ZHANG, ChangYan TIAN, Yu SUN, DengSha BAI, Gu FENG
Journal of Arid Land    2012, 4 (1): 43-51.   DOI: 10.3724/SP.J.1227.2012.00042
Abstract3980)      PDF (596KB)(3793)      
Previous studies documented that most desert plants can be colonized by arbuscular mycorrhizal (AM) fungi, however, little is known about how the dynamics of AM fungi are related to ephemerals in desert ecosystems. The dynamics of AM fungi with desert ephemerals were examined to determine the effects of host plant life stages on the development of AM fungi. Mean colonization of ephemeral annual plants was 45% lower than that of ephemeral perennial plants. The colonizations were much higher in the early part of the growing season than in later parts, peaking at flowering times. The phenology of AM fungi in root systems varied among different ephemerals. The density of AM fungal spores increased with the development of ephemeral annual plants, reached its maximum at flowering times, and then plateaued about 20 days after the aboveground senescence. A significant positive correlation was found between AM fungi spore density and biomass of ephemeral annual plants. The life cycles of AM fungi associated with desert ephemerals were very short, being about 60–70 days. Soil temperature and water content had no direct influence on the development of AM fungal spores. We concluded that the development of AM fungi was in response to desert ephemeral phenology and life history strategy.
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Anatomical and morphological characteristics of Populus euphratica in the lower reaches of Tarim River under extreme drought environment
Li ZHUANG, YaNing CHEN, WeiHong LI, ZhongKe WANG
Journal of Arid Land    2011, 3 (4): 261-267.   DOI: 10.3724/SP.J.1227.2011.00261
Abstract3958)      PDF (1268KB)(5222)      
Populus euphratica Oliv. is an old desert tree species that has been naturalized and invades zones along the watercourses in many arid and semiarid regions. The plant species developed some plasticity to adapt to the gradual environmental gradients. The aim of this study was to test the hypothesis that the changes in leaf morphology of P. euphratica reflect the adaptability of the plant to the unique environment of the lower reaches of Tarim River in China. The foliar architecture, blade epidermal and internal anatomies of P. euphratica were analyzed at different sites along the Tarim River. Compared with the abaxial surface of the leaves, their adaxial surface has more hairs, a greater stomatal density and opening, higher mesophyll proportion, and increased blade thickness, palisade width, and epidermal thickness. The long trichome of the roots found at site 6 in the Yinsu section may be an adapted structure of the plants in arid areas. The mature leaves of P. euphratica have comparatively more epidermis and cuticles, well developed palisades and more chloroplasts at different sites compared to the young leaves. Foliar morphological and anatomical variability in P. euphratica may be considered an adaptive advantage that enables leaves to develop and function in different habitats, marked by strong variations in solar radiation, air temperature, humidity and water table.
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Distribution and migration of houbara bustard (Chlamydotis undulata) in China
XingYi GAO, Olivier COMBREAU, JianFang QIAO, WeiKang YANG, Jun YAO, KeFen XU
Journal of Arid Land    DOI: 10.3724/SP.J.1227.00074
Abstract3956)      PDF (230KB)(2688)      
The distribution and migration of houbara bustard in China was studied by range investigation and tracking through PTT satellite transmitter from 1997 to 2004. The houbara bustard occurs in the Junggar Basin, north part of Tacheng Basin and valley of Ulungur river in northern Xinjiang, southern part of Turpan Basin and Barkol in eastern Xinjiang. In Inner Mongolia, the houbara bustard occurs in Urathouqi, Alxahouqi and Ejinaqi. In Gansu province, the houbara bustard occurs in Wuwei, Minqin and Shandan. The whole range is not contiguous area. Houbara bastard started migration from Junggar Basin in northern Xinjiang, Turpan Basin and Barkol in eastern Xinjiang, Wuwei in western Gansu Province and Bayan Nur in western Inner Mongolia in the middle of September. Flying to the west and northwest, via Junggar Basin and area between Bole and Habahe in northern Xinjiang, entered Kazakhstan, they turned toward southwest, passed Uzbekistan and Turkmenistan, arrived in Arabia Bay of southern Iran or flied over Afghanistan, arrived in southern Pakistan for wintering. The whole migration usually took 35 ± 13 days covering a distance of 4 800-7 000 km. In the next year, houbara went back to the breeding grounds in China through the same routes at the beginning of March. However, it took the birds 64 ± 17 days to finish the spring migration. They arrived in breeding site between middle of April and late May. The sub-adults arrived later and did not breed.
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The migration of total dissolved solids during natural freezing process in Ulansuhai Lake
Yan ZHANG, ChangYou LI, XiaoHong SHI, Chao LI
Journal of Arid Land    2012, 4 (1): 85-94.   DOI: 10.3724/SP.J.1227.2012.00085
Abstract3947)      PDF (833KB)(2832)      
High total dissolved solids (TDS) content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the object of study. Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness. TDS profiles were drawn to show the distribution of TDS and to describe TDS migration. The results showed that about 80% (that is 3.602×108 kg) of TDS migrated from ice to water during the whole growth period of ice. Within ice layer, TDS migration only occurred during initial ice-on period, and then per-ished. The TDS in ice decreased with increasing ice thickness, following a negative exponential-like trend. Within under-ice water, the TDS migrated from ice-water interface to the entire water column under the effect of concentration gradient until the water TDS content was uniform. In winter, 6.044×107 kg (16.78% of total TDS) TDS migrated from water to sediment, which indicated that winter is the best time for dredging sediment. The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River. The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate, which reveals that ice growth rate is one of the determinants of TDS migration. The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.
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Effects of emitter discharge rates on soil salinity distribution and cotton ( Gossypium hirsutum L.) yield under drip irrigation with plastic mulch in an arid region of Northwest China
Journal of Arid Land    2013, 5 (1): 51-59.   DOI: 10.1007/s40333-013-0141-7
Abstract3805)      PDF (661KB)(3087)      
 A field experiment was carried out to investigate the effects of different emitter discharge rates under drip irrigation on soil salinity distribution and cotton yield in an extreme arid region of Tarim River catchment in Northwest China. Four treatments of emitter discharge rates, i.e. 1.8, 2.2, 2.6 and 3.2 L/h, were designed under drip irrigation with plastic mulch in this paper. The salt distribution in the range of 70-cm horizontal distance and 100-cm vertical distance from the emitter was measured and analyzed during the cotton growing season. The soil salinity is expressed in terms of electrical conductivity (dS/m) of the saturated soil extract (ECe), which was measured using Time Domain Reflector (TDR) 20 times a year, including 5 irrigation events and 4 measured times before/after an irrigation event. All the treatments were repeated 3 times. The groundwater depth was observed by SEBA MDS Dipper 3 automatically at three experimental sites. The results showed that the order of reduction in averaged soil salinity was 2.6 L/h > 2.2 L/h > 1.8 L/h > 3.2 L/h after the completion of irrigation for the 3-year cotton growing season. Therefore, the choice of emitter discharge rate is considerably important in arid silt loam. Usually, the ideal emitter discharge rate is 2.4–3.0 L/h for soil desalinization with plastic mulch, which is advisable mainly because of the favorable salt leaching of silt loam and the climatic conditions in the studied arid area. Maximum cotton yield was achieved at the emitter discharge rate of 2.6 L/h under drip irrigation with plastic mulch in silty soil at the study site. Hence, the emitter discharge rate of 2.6 L/h is recommended for drip irrigation with plastic mulch applied in silty soil in arid regions.
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Impacts of temperature and precipitation on runoff in the Tarim River during the past 50 years
YuTing FAN, YaNing CHEN, WeiHong LI, HuaiJun WANG, XinGong LI
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00220
Abstract3752)      PDF (537KB)(3668)      
The relationship between climate change and water resources in?the Tarim River was analyzed by combining the temperature, precipitation and streamflow data from 1957 to 2007 from the four headstreams of the Tarim River (Aksu, Hotan,?Yarkant and Kaidu rivers) in the study area. The long-term trend of the hydrological?time series including temperature, precipitation and streamflow were studied using correlation analysis and partial correlations analysis. Holt double exponential smoothing was used to fit the trends between streamflow and the two climatic factors of Aksu River, Hotan River and Yarkant River. The streamflow of the main stream was forecasted by Autoregressive Integrated Moving Average Model (ARIMA) modeling by the method of time series analysis. The results show that the temperature experienced a trend of monotonic rising. The precipitation and runoff of the four headstreams of the Tarim River increased, while the inflow to the headstreams increased and the inflow into the Tarim River decreased. Changes of temperature and precipitation had a significant impact on runoff into the four headstreams of the Tarim River: the precipitation had a positive impact on water flow in the Aksu River, Hotan River and Kaidu River, while the temperature had a positive impact on water flow in the Yarkant River. The results of Holt double exponential smoothing showed that the correlation between the independent variable and dependent variable was relatively close after the model was fitted to the headstreams, of which only the runoff and temperature values of Hotan River showed a significant negative?correlation. The forecasts by the ARIMA model for 50 years of annual runoff at the Allar station followed the pattern of the measured data for the same years. The short-term forecasts beyond the observed series adequately captured the pattern in the data and showed a decreasing tendency in the Tarim River flow of 3.07% every ten years. The results showed that global warming accelerated the water recharge process of the headstreams. The special hydrological characteristics of the arid area determined the significant association between streamflow and the two climatic factors studied. Strong glacier retreat is likely to bring a series of flood disasters within the study area.
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Impact of climate factors on runoff in the Kaidu River watershed: path analysis of 50-year data
XueMei LI, LanHai LI, LingPeng GUO, FeiYun ZHANG, Suwannee ADSAVAKULCHAI, Ming SHANG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00132
Abstract3704)      PDF (398KB)(3083)      
Runoff formation is a complex meteorological-hydrological process impacted by many factors, especially in the inland river basin. Based on the data of daily mean air temperature, precipitation and runoff during the period of 1958-2007 in the Kaidu River watershed, this paper analyzed the changes in air temperature, precipitation and runoff and revealed the direct and indirect impacts of daily air temperature and precipitation on daily runoff by path analysis. The results showed that mean temperature time series of the annual, summer and autumn had a significant fluctuant increase during the last 50 years (P?
The development and progress of soil wind erosion are influenced by the factors of climate, terrain, soil and vegetation, etc. This paper, taking Tazhong region, a town in the centre of the Taklimakan Desert, as an example and using comparative and quantitative methods, discussed the effects of climate, surface roughness (including vegetation cover) and surface soil properties on soil wind erosion. The results showed that the climate factor index C of annual wind erosion is 28.3, while the maximum of C is 13.9 in summer and it is only 0.7 in winter. The value of C has a very good exponential relationship with the wind speed. In Tazhong region, the surface roughness height is relatively small with a mean of 6.32 × 10-5 m, which is in favor of soil wind erosion. The wind erosion is further enhanced by its sandy soil types, soil particle size, lacking of vegetation and low soil moisture content. The present situation of soil wind erosion is the result of concurrent effects of climate, vegetation and surface soil properties.
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Effects of parasitic plant Cistanche deserticola on chlorophyll a fluorescence and nutrient accumulation of host plant Haloxylon ammodendron in the Taklimakan Desert
Li LI, XinWen XU, YongQiang SU, Wei HAN, PengFei TU
Journal of Arid Land    2012, 4 (3): 342-348.   DOI: 10.3724/SP.J.1227.2012.00342
Abstract3640)      PDF (468KB)(3172)      
The parasitic plant Cistanche deserticola attaches to Haloxylon ammodendron, a perennial shrub with high tolerance to salinity and drought. However, little was known about the parasite-host relation between the two species. Effects of the parasite on chlorophyll a fluorescence and nutrient accumulation in the host plant ( H. ammodendron) were investigated in the Taklimakan Desert. Some photosynthetic parameters of both host and non-host H. ammodendron plants were measured by in vivo chlorophyll a fluorescence technology in the field. The assimilating branches of host and non-host plants were collected and nutrient and inorganic ion contents were analyzed. The results from field experiments showed that the infection of C. deserticola reduced the non-photochemical quenching of the variable chlorophyll fluorescence ( NPQ) and the potential maximum quantum yield for primary photochemistry ( Fv/Fm) of the host. Compared with non-host plants, the host H. ammodendron had low nutrient, low inorganic ion contents (Na + and K +) and low K +/Na + ratios in the assimilating branches. It suggested that C. deserticola infection reduced the nutrient acquisition and caused damage to the photoprotection through thermal dissipation of the energy of the photosystem II in the host, resulting in a decrease in the tolerance to salinity and high radiation. It was concluded that the attachment of the parasite plant ( C. deserticola) had negative effects on the growth of its host.
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The impact of land use change on soil organic carbon and labile organic carbon stocks in the Longzhong region of Loess Plateau
LiHua ZHANG, ZhongKui XIE, RuiFeng ZHAO, YaJun WANG
Journal of Arid Land    2012, 4 (3): 241-250.   DOI: 10.3724/SP.J.1227.2012.00241
Abstract3636)      PDF (4241KB)(6719)      
Land use change (LUC) is widely recognized as one of the most important driving forces of global carbon cycles. The soil organic carbon (SOC) and labile organic carbon (LOC) stores were investigated at arable land (AL), artificial grassland (AG), artificial woodland (AW), abandoned arable land (AAL) and desert steppe (DS) in the Longzhong region of the Loess Plateau in Northwest China. The results showed that conversions from DS to AL, AL to AG and AL to AAL led to an increase in SOC content, while the conversion from DS to AW led to a decline. The differences in SOC content were significant between DS and AW at the 20–40 cm depth and between AL and AG at the 0–10 cm depth. The SOC stock in DS at the 0–100 cm depth was 39.4 t/hm 2, increased by 28.48% after cultivation and decreased by 19.12% after conversion to AW. The SOC stocks increased by 2.11% from AL to AG and 5.10% from AL to AAL. The LOC stocks changed by a larger magnitude than the SOC stocks, which suggests that it is a more sensitive index of carbon dynamics under a short-term LUC. The LOC stocks increased at 0–20 cm and 0–100 cm depths from DS to AW, which is opposite to that observed for SOC. The proportion of LOC to SOC ranged from 0.14 to 0.20 at the 0–20 cm depth for all the five land use types, indicating low SOC dynamics. The allocation proportion of LOC increased for four types of LUC conversion, and the change in magnitude was largest for DS to AW (40.91%). The afforestation, abandonment and forage planting on arable land led to sequestration of SOC; the carbon was lost initially after afforestation. However, the carbon sink effect after abandonment may not be sustainable in the study area.
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Two-way coupling of unsaturated-saturated flow by integrating the SWAT and MODFLOW models with application in an irrigation district in arid region of West China
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00164
Abstract3585)      PDF (340KB)(3471)      
This paper presents the realization of two-way coupling of the unsaturated-saturated flow interactions of the SWAT2000 and MODFLOW96 models on the basis of the integrated surface/groundwater model SWATMOD99, and its application in Hetao Irrigation District (HID), Inner Mongolia, China. Major revisions and enhancements were made to the SWAT2000 and MODFLOW models for simulating the detailed hydrologic budget and coupled unsaturated and saturated interactions, and irrigation canal hydrology for the HID. The simulation results of seasonal groundwater recharge to and evaporate from the shallow groundwater, and the annual water budget over the district are presented and discussed. The results implied the necessity of two-way coupling of the unsaturated-saturated interactions when groundwater is shallow, and the feasibility of making comprehensive use of the information coming from both the surface water and groundwater models to make a more physically-based assessment of the coupled interactions.
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Spatial heterogeneity of soil water content in the reversion process of desertification in arid areas
QuanLin MA, Fang CHENG, YouJun LIU, FangLin Wang, DeKuai ZHANG, HuJia JIN
Journal of Arid Land    2011, 3 (4): 268-277.   DOI: 10.3724/SP.J.1227.2011.00268
Abstract3556)      PDF (4040KB)(3421)      
 Sandy soils in arid, rain-fed environments have low and limited water content, which is a principal factor limiting vegetation development, and a key constraint controlling the structure and functions of the ecological systems in arid areas. The spatial heterogeneity of soil water content is a major soil property, and a focus of soil science and hydrology. On the southern edge of the Tengger Desert, sample plots were selected from mobile sand dunes in desertified lands that had been enclosed for 5, 15 and 25 years, respectively. This study explored the dynamic and spatial heterogeneity of soil water content in these different layers of soil that were also in the reversion process of desertification. The results showed that the soil water content of the mobile sand dunes was highest when in the initial stages of the reversion process of desertification, while the soil water content in the 0–20 cm, 20–40 cm and 40–60 cm layers of soil was 1.769%, 3.011%, and 2.967% respectively, presenting a restoring tendency after 25 years of enclosure. There were significant differences, as a whole, in the soil water content among different restoration stages and different soil layers, respectively. Changes in soil water content, in different soil layers, at different restoration stages, exhibited exponential or spherical patterns. The spatial distribution of soil water content exhibited a mosaic patch pattern with obvious spatial heterogeneity. The ratio of the heterogeneity of spatial autocorrelation to gross spatial heterogeneity was greater than 50%. The gross spatial heterogeneity of the 0–20 cm layer of soil improved gradually, while those of the 20–40 cm and 40–60 cm layers improved initially, then weakened in the reversion process of desertification. This study revealed that restoration with sand-binding vegetation reduced soil water content, and increased its spatial heterogeneity in arid areas. However, after 25 years of vegetation-soil system restoration, the soil water content started to increase and its spatial heterogeneity started to weaken. These results will further benefit the understanding of the ecological mechanism between soil water and sand-binding vegetation.
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Regional partitioning of agricultural non-point source pollution in China using a projection pursuit cluster model
XinHu LI, ChengYi ZHAO, Bin WANG, Garry FENG
Journal of Arid Land    2011, 3 (4): 278-284.   DOI: 10.3724/SP.J.1227.2011.00278
Abstract3532)      PDF (441KB)(3527)      
A projection pursuit cluster (PPC) model was used to analyze the regional partitioning of agricultural non-point source pollution in China. The environmental factors impacting the agricultural non-point source pollution were compiled into a projection index to set up the projection index function. A novel optimization algorithm called Free search (FS) was introduced to optimize the projection direction of the PPC model. By making the appropriate improvements as we explored the use of the algorithm, it became simpler, and developed better exploration abilities. Thus, the multi-factor problem was converted into a single-factor cluster, according to the projection, which successfully avoided subjective disturbance and produced objective results. The cluster results of the PPC model mirror the actual regional partitioning of the agricultural non-point source pollution in China, indicating that the PPC model is a powerful tool in multi-factor cluster analysis, and could be a new method for the regional partitioning of agricultural non-point source pollution.
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Effects of deficit irrigation with saline water on spring wheat growth and yield in arid Northwest China
Jing JIANG, ZaiLin HUO, ShaoYuan FENG, ShaoZhong KANG, FenXing WANG, ChaoBo ZHANG
Journal of Arid Land    2013, 5 (2): 143-154.   DOI: 10.1007/s40333-013-0152-4
Abstract3523)      PDF (420KB)(4336)      
Field experiments were conducted in 2008 and 2009 to study the effects of deficit irrigation with saline water on spring wheat growth and yield in an arid region of Northwest China. Nine treatments included three salinity levels s1, s2 and s3 (0.65, 3.2, and 6.1 dS/m) in combination with three water levels w1, w2 and w3 (375, 300, and 225 mm). In 2008, for most treatments, deficit irrigation showed adverse effects on wheat growth; meanwhile, the effect of saline irrigation was not apparent. In 2009, growth parameters of w1 treatments were not always optimal under saline irrigation. At 3.2 and 6.1 dS/m in 2008, the highest yield was obtained by w1 treatments, however, in 2009, the weight of 1,000 grains and wheat yield both followed the order w2 > w1 > w3. In this study, spring wheat was sensitive to water deficit, especially at the booting to grain-filling stages, but was not significantly affected by saline irrigation and the combination of the two factors. The results demonstrated that 300-mm irrigation water with a salinity of less than 3.2 dS/m is suitable for wheat fields in the study area.
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Quantifying the impacts of soil water stress on the winter wheat growth in an arid region, Xinjiang
ChengYi ZHAO, Yu SHENG, Yilihm·Yimam
Journal of Arid Land    DOI: 10.3724/SP.J.1227.00034
Abstract3504)      PDF (328KB)(2326)      
Wheat growth in response to soil water deficit play an important role in yield stability. A field experiment was conducted for winter wheat (Triticum aestivum L.) during the period of 2002–2005 to evaluate the effects of limited irrigation on winter wheat growth. 80%, 70%, 60%, 50% and 40% of field capacity was applied at different stages of crop growth. Photosynthetic characteristics of winter wheat, such as photosynthesis rate, transpiration rate, stomatal conductance, photosynthetically active radiation, and soil water content, root and shoot dry mass accumulation were measured, and the root water uptake and water balance in different layer were calculated. Based on the theory of unsaturated dynamic, a one-dimensional numerical model was developed to simulate the effect of soil water movement on winter wheat growth using Hydrus-1 D. The soil water content of stratified soil in the experimental plot was calculated under deficit irrigation. The results showed that, in different growing periods, evapotranspiration, grain yield, biomass, root water uptake, water use efficiency, and photosynthetic characteristics depended on the controlled ranges of soil water content. Grain yield response to irrigation varied considerably due to differences in soil moisture contents and irrigation scheduling between seasons. Evapotranspiration was largest in the high soil moisture treatment, and so was the biomass, but this treatment did not produce the highest grain yield and root water uptake was relatively low. Maximum depth of root water uptake is from the upper 80 cm in soil profile in jointing stage and dropped rapidly upper 40 cm after heading stage, and the velocity of root water uptake in latter stage was less than that in middle stage. The effect of limited irrigation treatment on photosynthesis was complex owing to microclimate. But root water uptake increased linearly with harvest yield and improvement in the latter gave better root water uptake under limited irrigation conditions. Appropriately controlled soil water contents can improve the root water uptake and grain yield. Consistently high values of root water uptake and grain yield were produced under conditions of mild water deficit at the seedling and start of regrowth to stem-elongation stages, in addition to a further soil water depletion at the physiological maturity to harvest stage. We suggest that periods of mild soil water depletion in the early vegetative growth period together with severe soil water depletion in the maturity stage of winter wheat is an optimum for limited irrigation regime in this oasis. Considerable potential for further improvement in agricultural water use efficiency in the arid zone depends on effective conservation of moisture and efficient use of the limited water.
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Effects of soil moisture on cotton root length density and yield under drip irrigation with plastic mulch in Aksu Oasis farmland
ChengYi ZHAO, YingYu YAN, Yilihamu Yimamu, JuYan LI, ZhiMin ZHAO, LaoSheng WU
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00243
Abstract3503)      PDF (249KB)(3166)      
Effects of soil moisture on cotton root length density (total root length per unit soil volume) and yield under drip irrigation with plastic mulch were studied through field experiments. The results indicate that spatial distributions of root length density of cotton under various water treatments were basically similar. Horizontally, both root length densities of cotton in wide and narrow rows were similar, and higher than that between mulches. Vertically, root length density of cotton decreased with increasing soil depth. The distribution of root length density is different under different irrigation treatments. In conditions of over-irrigation, the root length density of cotton between mulches would increase. However, it would decrease in both the wide rows and narrow rows. The mean root length density of cotton increased with increasing irrigation water. Water stress caused the root length density to increase in lower soil layers. There is a significant correlation between root length density and yields of cotton at the flower-boll and wadding stages. The regression between irrigation amount and yield of cotton can be expressed as y = -0.0026x2+18.015x-24845 (R2 = 0.959). It showed that the irrigation volume of 3,464.4?m3/hm2 led to optimal root length density. The yield of cotton was 6,360?.8?kg/hm2 under that amount of irrigation.
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The qanats of Xinjiang: historical development, characteristics and modern implications for environmental protection
WenJun HU, JieBin ZHANG, YongQiang LIU
Journal of Arid Land    2012, 4 (2): 211-220.   DOI: 10.3724/SP.J.1227.2012.00211
Abstract3493)      PDF (343KB)(4686)      
In China, qanats (kan’erjing/karez) exist only in Xinjiang Uygur autonomous region, being one form of traditional irrigation technology that made great contributions to oasis civilizations. There are different opinions on the origin and date of the qanats in Xinjiang due to a lack of adequate evidences. And uncontrolled over-exploitation of groundwater by pumping wells, as well as the expansion of surface water interventions nowadays, has caused serious impacts on not only the qanats, but also local ecological environments. There exist long-time arguments on whether the qanats should be restored or preserved. This study aimed to examine the historical development, geological conditions and characteristics, and modern implications of the qanats for oasis environmental protection, and to discuss the initiatives taken by local governments. The whole Xinjiang Uygur autonomous region was included as the study area, with a specific focus on Turpan prefecture. The materials and data were obtained from literature review and governmental documentation. Based on a systematic examination of three prevailing theories on the origination of Xinjiang’s qanats, it is suggested modern archaeological techniques could be good solutions to explore the origination in addition to historical records used normally. Although qanats fail to fully meet today’s enormous water demands, their rich historical, cultural, ecological and environmental implications in arid areas should not be underestimated. As a cultural heritage and ecologically-friendly engineering creation, qanat systems shall be kept in good condition and function by a valuable number. Recent initiatives to protect and restore target qanat systems in Xinjiang could provide positive examples for the practices in other regions of the world where the protection and restoration of qanats or similar technologies are desired.
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Impact of nitrogen addition on plant community in a semi-arid temperate steppe in China
Ling SONG, XueMei BAO, XueJun LIU, FuSuo ZHANG
Journal of Arid Land    2012, 4 (1): 3-10.   DOI: 10.3724/SP.J.1227.2012.00003
Abstract3486)      PDF (372KB)(3206)      
 Increased nitrogen (N) deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels (0, 3, 6, 12, 24, and 48 g N/(m 2×a)) were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/(m 2×a) above ambient N deposition (1.2 g N/(m 2×a)), led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses (PB) but decrease perennial forbs (PF), and induce a slight change in the biomass of shrubs and semi-shrubs (SS). The biomass of annuals (AS) and perennial rhizome grasses (PR) accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.
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Sand flux estimation during a sand-dust storm at Tazhong area of Taklimakan Desert, China
XingHua YANG, XiaoLiang XU, Qing HE, Ali Mamtimin, Bo YU, ShiHao TANG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2011.00199
Abstract3465)      PDF (323KB)(2448)      
In this paper, the sand transport during a sand-dust storm in the Tazhong area of the central Taklimakan Desert from 11:29 to 23:56 on July 19, 2008 was observed and measured in real time. The sand flux at Tazhong was estimated using sand transport empirical formulas. The critical friction velocity at Tazhong was 0.24 m/s and the functional relation between the wind speed and sediment discharge at the height of 2 m was established. It was also found that the calculated values by Lettau's sediment discharge formula were close to those of the instrument measurements. The horizontal sand flux and the vertical sand flux during this sand-dust storm at Tazhong were respectively 258.67×10-4 kg/(m·s) and 40.07×10-7 kg/(m2·s).
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Influence of groundwater depth on species composition and community structure in the transition zone of Cele oasis
XiangYi LI, LiSha LIN, Qiang ZHAO, XiMing ZHANG, Frank M. THOMAS
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00235
Abstract3462)      PDF (162KB)(2133)      
The paper analyzes the hypothesis that the distribution of dominant plant species and characteristics of plant communities are related to groundwater depth. The results showed that variations of groundwater depth impacted distributions and characteristics of dominant plant communities. However, besides groundwater depth, the community composition and species diversity were also influenced by physiognomy of the habitat. Based on the similarity coefficient, the differences between dominant plant communities were significant at different groundwater depths. Compared with other results relating to desert vegetation and groundwater depth, variations of community distribution were similar at the large spatial scale. However, in this extremely arid region, there were significant differences in community type and community succession when compared with other arid regions, especially in relationship to deep groundwater depth. With groundwater depth from deep to shallow, communities transformed with the sequence of Alhagi communities, Tamarix spp. communities, Populus communities, Phragmites communities, and Sophora communities. At groundwater depth of less than 6.0 m, the community type and composition changed, and the species diversity increased. Among these dominant species, Tamarix exhibited the biggest efficiency in resource utilization according to niche breadth, which means it possessed the best adaptability to environmental conditions at the oasis margins.
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Winter habitat use of snow leopards in Tomur National Nature Reserve of Xinjiang, Northwest China
Feng XU, Ming MA, WeiKang YANG, David BLANK, YiQun WU, Thomas MCCARTHY, Bariusha MUNKHTSOG
Journal of Arid Land    2012, 4 (2): 191-195.   DOI: 10.3724/SP.J.1227.2012.00191
Abstract3419)      PDF (395KB)(2667)      
Snow leopards are one of the least known large cats, the population of which has dramatically de-creased. Their habitat loss was considered the main reason for the decline during the last decade, but their habitat preferences are still not well known. In this paper, we studied the winter habitat preferences of snow leopards in the Tomur National Nature Reserve (TNNR) in Northwest China during 2004–2005. We used sign surveys and transects to study the winter habitat selection of snow leopards. The results indicated that snow leopards showed a preference for habitat variabilities in slope aspect, vegetation cover, dominant topographical features, landform ruggedness and grazing status. We found that prey availability and dominant topographical features were the most important factors that determined the winter habitat selection of snow leopards. Our results supported the idea that the habitat preferences of snow leopards are a tradeoff between suitable habitat features and avoidance of potential human interactions.
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Species composition, distribution patterns and ecological functions of biological soil crusts in the Gurbantunggut Desert
YuanMing ZHANG, Nan WU, BingChang ZHANG, Jing ZHANG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00180
Abstract3409)      PDF (301KB)(3483)      
As one of the most important biological factors that maintain the stability of the largest fixed and semi-fixed desert in China, the Gurbantunggut Desert, the biological soil crusts (BSCs) develop well and play critical ecological roles in the desert ecosystem. In this paper, we briefly summarize our research findings since 2002 including species composition, distribution pattern and ecological functions of BSCs in the desert. Our results indicate abundant species diversity of BSCs in the Gurbantunggut Desert in comparison to other deserts in China. At the scales of sand dune or whole desert, the distribution patterns of BSCs are location-specific. The existence of BSCs in this desert could: (1) accelerate the formation of desert soil and the weathering of minerals; (2) accumulate organic matter in surface soil through related species in soil crusts; (3) enhance the abilities of sand surface to resist wind erosion; (4) influence seed germination of vascular plants; and (5) enhance the production of dew deposition on sandy soil surface.
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Monophyly and infrageneric variation of Corispermum L. (Chenopodiaceae), evidence from sequence data psbB-psbH, rbcL and ITS
JuanJuan XUE, MingLi ZHANG
Journal of Arid Land    2011, 3 (4): 240-253.   DOI: 10.3724/SP.J.1227.2011.00240
Abstract3391)      PDF (1766KB)(6002)      
Corispermum is one of the most problematic taxonomic genera in Chenopodiaceae. To understand the phylogeny and infrageneric variation of Corispermum, we sequenced the nuclear ribosomal ITS region and two chloroplast DNA regions (rbcL and psbB-psbH) of 22 species and three varieties of Corispermum and the related genus Agriophyllum. Several representative species of Salsola, Suaeda, Chenopodium, Kalidium and Camphorosma served as outgroups. Our phylogenetic trees confirm that the tribe Corispermeae is monophyletic, Corispermum and Agriophyllum have a close relationship. Corispermum is demonstrated to be monophyletic, and contains at least four clades which, consequently, are served as the foundation of the infrageneric sectional variation of Corispermum, in terms of a combination of molecular data and morphological characters. The evolution of morphological characters for fruit wing and apex, two important characters in generic classification, is consistent with the sectional division of Corispermum, especially to the East Asian and Chinese taxa.
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Cited: Baidu(5)
Altitudinal patterns of stand structure and herb layer diversity of Picea schrenkiana forests in the central Tianshan Mountains, Northwest China
LiPing LI, XiangPing WANG, Stefan ZERBE, LiYun ZHANG, JingYun FANG
Journal of Arid Land    2011, 3 (4): 254-260.   DOI: 10.3724/SP.J.1227.2011.00254
Abstract3376)      PDF (727KB)(3486)      
Altitude is a useful indicator to examine patterns of forest structure and species diversity in relation to environmental factors. In this study, the altitude patterns of forest stand structure and species diversity were analyzed across 20 plots in the Tianchi Nature Reserve, Northwest China. The results showed that mean stem height (Hm), maximum stem height (Hmax) and mean stem diameter at breast height (Dm) of Picea schrenkiana trees all decreased significantly with increasing altitude. Potential tree height (H*) decreased while stem taper increased significantly as altitude increased, suggesting remarkable altitudinal changes in biomass allocation between the diameter and height growth of Picea schrenkiana. Understory herbaceous richness increased significantly with increasing altitude, or with decreasing total basal area (TBA), Hm and stand volume (Volume). High light availability for understory herbs might account for the higher species richness at high altitude. Sorensen Index decreased significantly with the increase in altitude intervals, while the Cody Index demonstrated a converse pattern, suggesting greater differences in species composition with larger distances.
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Molecular phylogeny of tribe Atraphaxideae (Polygonaceae) evidenced from five cpDNA genes
YanXia SUN, MingLi ZHANG
Journal of Arid Land    2012, 4 (2): 180-190.   DOI: 10.3724/SP.J.1227.2012.00180
Abstract3375)      PDF (175KB)(3603)      
Traditionally, Atraphaxis, Calligonum, Pteropyrum and Parapteropyrum are included in the tribe Atraphxideae. Recently, sequence data has revealed that this tribe is not monophyletic. The structure of the tribe was examined by adding more taxa and sequences to clarify the congruence between morphology and molecular phylogeny, the systematic placements of four genera in Polygonaceae, as well as the infra-generic relationships of Atraphaxis and Calligonum within Atraphaxideae. Five chloroplast genes, atpB- rbcL, psbA- trnH, trnL– trnF, psbK- psbI, and rbcL of Atraphaxis, Calligonum, Pteropyrum, and Parapteropyrum were sequenced. The non-monophyly of Atraphaxideae was confirmed. Atraphaxis and Calligonum, respectively, formed a monophyletic group that was well supported. Calligonum is closely related to Pteropyrum; Atraphaxis is sister to Polygonum s. str.; and Parapteropyrum is allied with Fagopyrum. Although the morphology suggested the four genera should form a tribe, the molecular data indicated Atraphaxideae was not one monophyletic group. The clades identified within Atraphaxis corresponded well with the current sectional classification based on morphological features. As for Calligonum, Medusa was identified as a non-monophyletic section
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Saline dust storms and their ecological impacts in arid regions
Jilili Abuduwaili, DongWei LIU, GuangYang WU
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00144
Abstract3341)      PDF (210KB)(3896)      
In many arid and semiarid regions, saline playas represent a significant source of unconsolidated sediments available for aeolian transport, and severe saline dust storms occur frequently due to human disturbance. In this study, saline dust storms are reviewed systematically from the aspects of concept, general characteristics, conditions of occurrence, distribution and ecological impact. Our researches showed that saline dust storms are a kind of chemical dust storm originating in dry lake beds in arid and semiarid regions; large areas of unconsolidated saline playa sediments and frequent strong winds are the basic factors to saline dust storm occurrence; there are differentiation characteristics in deposition flux and chemical composition with wind-blown distance during saline dust storm diffusion; and saline dust storm diffusion to some extent increases glacier melt and results in soil salinization in arid regions. An understanding of saline dust storms is important to guide disaster prevention and ecological rehabilitation.
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Causes of recurring drought patterns in Xinjiang, China
Rashed MAHMOOD, ShuangLin LI, Babar KHAN
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00279
Abstract3334)      PDF (621KB)(2603)      
Xinjiang Uygur Autonomous Region of China, with its unique topography and geographical location receives very less precipitation in summer as compared with other parts of China. The region is a land locked where moisture is supplied only by westerly winds from Atlantic Ocean as the moisture coming from Indian Ocean is mostly blocked by the Himalayas Range and the Tibetan plateau. In such a scenario, Xinjiang faces severe drought conditions offering significant challenges to water management. In this paper, we analyzed the drought periods in Xinjiang and discussed the various factors that might have influenced precipitation over the past forty-four years. For this purpose, we defined three periods of consecutive four years for high and low precipitation intensities. The average observed precipitation was 1.05 mm/day and 0.7 mm/day in summer (June-July-August) for the Tianshan Mountain region and Junggar Basin of Xinjiang, respectively. The drought conditions indicated that high sea level pressure, wind divergence and low convection were the prominent features that caused the droughts, which often do not allow the condensation process to coagulate the tiny water droplets into relatively large raindrops reducing the amount of precipitation in the region. The period of 1983-1986 is the lowest precipitation interval indicating the severe drought in the western Xinjiang (i.e western Tianshan Mountain region), for which, less moisture availability, strong divergence and less convection could be the most influencing factors.
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Effect of vegetation on soil water retention and storage in a semi-arid alpine forest catchment
Chao WANG, ChuanYan ZHAO, ZhongLin XU, Yang WANG, HuanHua PENG
Journal of Arid Land    2013, 5 (2): 207-219.   DOI: 10.1007/s40333-013-0151-5
Abstract3327)      PDF (2341KB)(7112)      
The runoff generated from mountainous regions is recognized as the main water source for inland river basins in arid environments. Thus, the mechanisms by which catchments retain water in soils are to be understood. The water storage capacity of soil depends on its depth and capacity to retain water under gravitational drainage and evapotranspiration. The latter can be studied through soil water retention curve (SWRC), which is closely related to soil properties such as texture, bulk density, porosity, soil organic carbon content, and so on. The present study represented SWRCs using HYDRUS-1D. In the present study, we measured physical and hydraulic properties of soil samples collected from Sabina przewalskii forest (south-facing slope with highest solar radiation), shrubs (west-facing slope with medium radiation), and Picea crassifolia forest (north-facing slope with lowest radiation), and analyzed the differences in soil water storage capacity of these soil samples. Soil water content of those three vegetation covers were also measured to validate the soil water storage capacity and to analyze the relationship between soil organic matter content and soil water content. Statistical analysis showed that different vegetation covers could lead to different soil bulk densities and differences in soil water retention on the three slope aspects. Sand content, porosity, and organic carbon content of the P. crassifolia forest were relatively greater compared with those of the S. przewalskii forest and shrubs. However, silt content and soil bulk density were relatively smaller than those in the S. przewalskii forest and shrubs. In addition, there was a significant linear positive relationship between averaged soil water content and soil organic matter content (P<0.0001). However, this relationship is not significant in the P. crassifolia forest. As depicted in the SWRCs, the water storage capacity of the soil was 39.14% and 37.38% higher in the P. crassifolia forest than in the S. przewalskii forest and shrubs, respectively, at a similar soil depth.
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Land cover change detection based on satellite data for an arid area to the south of Aksu in Taklimakan desert
Kiyoshi TSUCHIYA, Tamotsu IGARSHI, Muhtar QONG
Journal of Arid Land    DOI: 10.3724/SP.J.1227.2010.00014
Abstract3319)      PDF (827KB)(1586)      
An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.
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Interactions between water-land resources and oasis urban development at the northern slopes of the Tianshan Mountains, Xinjiang, China
Jun LEI, Wen DONG, Yu YANG, Jie LU, Thomas STERR
Journal of Arid Land    2012, 4 (2): 221-229.   DOI: 10.3724/SP.J.1227.2012.00221
Abstract3319)      PDF (390KB)(2476)      
Urban development in arid and semi-arid regions is largely constrained by fragile physical environ-ments. The characteristics of an urban settlement are different from those in other regions of China. This paper analyses the coupling characteristics and spatio-temporal variations for oasis urban development and water-land resources at the northern slopes of the Tianshan Mountains by principal component analysis and a coupling degree model. The result shows that the degree and change in regional use of water and land resources are different among the studied cities/counties during their development. The built-up areas of these cities/counties have changed little with increasing populations and urbanization levels, which well reflects that the urban development in arid and semi-arid regions is limited by oasis areas. Per capita amount of water supplied, however, presented a trend of slowed growth with increasing levels of urbanization. Water consumption gradually increased with urban development and the improvement of people's living standards, accompanied by enhanced water use efficiency. The level of urbanization can be assessed through the coupling degree between oasis urban development and the use of water and land resources. A high coupling degree represents a high level of comprehensive urban development and use of water-land resources. Alternatively, a low coupling degree denotes a low level of urban development and water-land resource use.
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Plant diversity-productivity patterns in the alpine steppe environment of the Central Tianshan Mountains
YuKun HU, KaiHui LI, YanMing GONG, Wei YIN
Journal of Arid Land    DOI: 10.3724/SP.J.1227.00043
Abstract3290)      PDF (209KB)(1629)      
The biodiversity-productivity relationship is an important topic in the research of biodiversity and ecosystem function. The plant diversity-productivity pattern is commonly unimodal and positively correlated. This paper researches the characteristics of plant diversity-productivity patterns in the Bayanbuluk alpine steppe in the central Tianshan Mountains, Xinjiang, China, and analyzes the effects of environmental factors on the distribution of plant communities, species composition, plant diversity and productivity in the steppe. The results show a positive correlation between plant diversity and productivity. DCCA (detrended canonical correspondence analysis) ordination reveals a significant relationship between the effects of air temperature, soil moisture content, available soil nitrogen, relative humidity and pH value on the distribution and composition of plant communities. There are significant correlations between the soil moisture content, relative humidity, pH value, air temperature and species richness and the aboveground biomass of Gramineae and Cyperaceae, and also significant correlations between the relative humidity, pH values and the total aboveground biomass of plant communities.
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Allometric response of perennial Pennisetum centrasiaticum Tzvel to nutrient and water limitation in the Horqin Sand Land of China
Wei MAO, TongHui ZHANG, YuLin LI, XueYong ZHAO, YingXin HUANG
Journal of Arid Land    2012, 4 (2): 161-170.   DOI: 10.3724/SP.J.1227.2012.00161
Abstract3275)      PDF (732KB)(2266)      
Optimal partitioning theory (OPT) suggests that plants should allocate relatively more biomass to the organs that acquire the most limited resources. The assumption of this theory is that plants trade off the biomass allocation between leaves, stems and roots. However, variations in biomass allocation among plant parts can also occur as a plant grows in size. As an alternative approach, allometric biomass partitioning theory (APT) asserts that plants should trade off their biomass between roots, stems and leaves. This approach can minimize bias when comparing biomass allocation patterns by accounting for plant size in the analysis. We analyzed the biomass allocation strategy of perennial Pennisetum centrasiaticum Tzvel in the Horqin Sand Land of northern China by treating samples with different availabilities of soil nutrients and water, adding snow in winter and water in summer. We hypothesized that P. centrasiaticum alters its pattern of biomass allocation strategy in response to different levels of soil water content and soil nitrogen content. We used standardized major axis (SMA) to analyze the allometric relationship (slope) and intercept between biomass traits (root, stem, leaf and total biomass) of nitrogen/water treatments. Taking plant size into consideration, no allometric relationships between different organs were significantly affected by differing soil water and soil nitrogen levels, while the biomass allocation strategy of P. centrasiaticum was affected by soil water levels, but not by soil nitrogen levels. The plasticity of roots, leaves and root/shoot ratios was ‘true’ in response to fluctuations in soil water content, but the plasticity of stems was consistent for trade-offs between the effects of water and plant size. Plants allocated relatively more biomass to roots and less to leaves when snow was added in winter. A similar trend was observed when water was added in summer. The plasticity of roots, stems and leaves was a function of plant size, and remained unchanged in response to different soil nitrogen levels.
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Simulating the vegetation-producing process in small watersheds in the Loess Plateau of China
Journal of Arid Land    2012, 4 (3): 300-309.   DOI: 10.3724/SP.J.1227.2012.00300
Abstract3240)      PDF (1908KB)(2921)      
Small watersheds are the basic composition unit of the Loess Plateau in China. An accurate estimation of vegetation net primary productivity (NPP) is of great significance for eco-benefit evaluation in small watershed management in this region. Here we describe the development and testing of a vegetation-producing process model (VPP) of a small watershed in the Loess Plateau. The model couples three modules: radiation adjustment; soil hydrological processes; and vegetation carbon assimilation. Model validation indicates that the VPP model can be used to estimate the NPP of small watersheds in the region. With the VPP model, we estimated the spatial NPP distributions in the Yangou watershed for 2007. The results show that in the Yangou watershed the NPP is relatively low, averaging 168 g C/(m 2•a). Trees and shrubs have a higher NPP than crops and grasses. The NPP is larger on the partly shaded and shaded slopes than on the partly sunny and sunny slopes. The NPP on the slopes increases gradually on 0–20° slopes and decreases slightly on slopes steeper than 20°. Our simulation indicates that the vegetation type is the most important factor in determining the NPP distribution in small watersheds in the Loess Plateau.
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