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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
Abstract6792)      PDF(pc) (468KB)(4797)       Save
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
Abstract6111)      PDF(pc) (377KB)(6399)       Save
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
Abstract4588)      PDF(pc) (8278KB)(4308)       Save
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
Abstract4519)      PDF(pc) (662KB)(8079)       Save
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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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
Abstract4165)      PDF(pc) (230KB)(2824)       Save
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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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
Abstract4151)      PDF(pc) (442KB)(4906)       Save
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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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
Abstract4118)      PDF(pc) (230KB)(3374)       Save
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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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
Abstract4081)      PDF(pc) (1268KB)(5367)       Save
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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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
Abstract4064)      PDF(pc) (596KB)(3923)       Save
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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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
Abstract4061)      PDF(pc) (1122KB)(3519)       Save
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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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
Abstract4053)      PDF(pc) (833KB)(3019)       Save
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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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
Abstract3937)      PDF(pc) (537KB)(4074)       Save
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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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
Abstract3874)      PDF(pc) (661KB)(3247)       Save
 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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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
Abstract3808)      PDF(pc) (398KB)(3275)       Save
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?