Spatio-temporal pattern and changes of evapotranspiration in arid Central Asia and Xinjiang of China

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 2,168.68×10 8 m 3 (with an evaporation/precipitation ratio of 1.05) and 9,741.03×10 8 m 3 (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.     

IRRIGATING WARPED SOILS——ANTHROPOGENIC SOIL IN ARID AND SEMI-ARID REGIONS OF CHINA

<正> The irrigating warped soils occur in the old irrigation areas of arid and semi-arid re-gions of China, and distributed from Zhangjiakou of Hebei province, through InnerMongolia Autonomous Region, Ningxia Hui Autonomous Region, Gansu province,Qinhai Province, down to Xinjiang Autonomous Region, including the arid subalpine rivervalleys in the western part of Tibet.     

BASIC IDEA OF TOURIST''''S ITINERARIES IN THE ARID AREA OF CHINA——Discussion of the Methodology for Designing the Itineraries in the Arid Area

<正> The aspect discussed in the present paper should ont be identified strictly with the natu-ral and geogrophical arid areas in the whole China, but only referred to the seven provincesas Shaanxi, Gansu, Qinhai, Xinjiang and Inner Mongolia. According to the real conditions of the development of tourism which was formedobjectively in the arid areas, it is necessary to consider comprehensively the influence by the     

Interdecadal variations of pan-evaporation at the southern and northern slopes of the Tianshan Mountains,China

Evaporation controlled by meteorological parameters plays a crucial role in hydrology,meteorology and water resources management.An insight view of long-term variation in evaporation will help understanding the effects of climate change and provide useful information for rational utilization of water resources,especially in the arid land where the shortage of water resources exists.However,the lack of data on evaporation led to difficulties in assessing the impacts of climate change on evaporation,especially in arid mountainous area.This study investigated the long-term variation of the pan-evaporation(Ep) measured by E601 type evaporation pan and its influencing climatic factors at both northern and southern slopes of the Tianshan Mountains in Xinjiang of China using the ensemble empirical mode decomposition method and Path analysis.The results revealed that Eps at both northern and southern slopes had obvious interdecadal variation within cycles of 3–4 and 7–8 years.Eps at both slopes sharply decreased in early 1980 s,but increased after late 1990 s.Path analysis showed that the 3–4 years cycle of Ep at the northern and southern slopes was mainly dependent upon actual water vapor pressure with a negative direct path coefficient of –0.515 and sunshine duration with a positive direct path coefficient of 0.370,respectively.The variation of Ep with cycle of 7–8 years at the northern slope was attributed to the wind speed with a direct path coefficient of 0.774.Average temperature had a direct path coefficient of 0.813 in 7–8 years cycle at the southern slope.The assessment of Ep variation and its causes provides information essential for a good understanding of hydrologic cycle and regional climate of arid mountainous regions in Xinjiang of China and offers a theoretical reference for distribution and utilization of water resources.     

Effects of irrigation on precipitation in the arid regions of Xinjiang,China

Soil moisture is an important parameter for the interaction between soil and atmosphere.It is the second important factor that influences climate change,next to sea surface temperature(SST).Most previous studies focused on the monsoon regions in East China,and only a few laid emphases on arid environments.In Xinjiang, which is located in Northwest China,the climate is typically arid and semi-arid.During the past 20 years,the precipitation in Xinjiang has shown a significant increasing trend,and it is closely related to oasis irrigation.This paper aims at discussing whether abnormal soil moisture in spring can be the signal to forecast summer precipitation.The effects of abnormal soil moisture due to farm irrigation in spring in arid environments on regional climate are investigated by using a regional climate model(RegCM3).The results indicate that positive soil moisture anomaly in irrigated cropland surface in May led to an increase in precipitation in spring as well as across the whole summer. The impact could last for about four months.The effects of soil moisture on the surface air temperature showed a time-lagging trend.The summer air temperature declined by a maximum amplitude of 0.8oC.The increased soil moisture could enhance evaporation and ascending motion in the low troposphere,which brought in more precipitation.The soil moisture affected regional weather and climate mainly by altering the surface sensible and latent heat fluxes.     

Vegetation cover change and the driving factors over northwest China

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.     

Evolution of groundwater recharge-discharge balance in the Turpan Basin of China during 1959–2021

Groundwater overexploitation is a serious problem in the Turpan Basin, Xinjiang Uygur Autonomous Region of China, causing groundwater level declines and ecological and environmental problems such as the desiccation of karez wells and the shrinkage of lakes. Based on historical groundwater data and field survey data from 1959 to 2021, we comprehensively studied the evolution of groundwater recharge and discharge terms in the Turpan Basin using the groundwater equilibrium method, mathematical stat...     

Distribution and migration of houbara bustard (Chlamydotis undulata) in China

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 Xin-jiang, 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.     

Groundwater hydrochemistry and isotope geochemistry in the Turpan Basin,northwestern China

The Turpan Basin is located in the arid zone of northwestern China and is a typical closed inland basin surrounded by high mountains. It is one of the most arid regions in the world and, as a result, the groundwater in this area is very important for both domestic and agricultural uses. In the present study, the relationships of major elements（K＋, Na＋, Ca2＋, Mg2＋, HCO3-, SO42- and Cl-） and environmental isotopes（δ18O, δ2H and T） in groundwater were analyzed to investigate the evolution of the regional hydrochemistry within the Turpan Basin. The hydrochemistry results demonstrate that groundwater with high total dissolved solids（TDS） concentration is dominated by sodium chloride（Na-Cl） and sodium sulfate（Na-SO4） type water, whereas that with low TDS concentration（typically from near mountain areas） is dominated by calcium bicarbonate（Ca-HCO3） type water. The evolution of groundwater hydrochemistry within the Turpan Basin is a result of calcium carbonate precipitation, evaporation concentration, cation exchange and dissolution of evaporites（i.e. halite, mirabilite and gypsum）. Furthermore, evaporite dissolution associated with irrigation practice plays a key role in the groundwater salinization, especially in the central part of the basin. Environmental isotopes reveal that the groundwater is recharged by precipitation in the mountain areas and fast vertical infiltration of irrigation return flow. In the southern sub-basin the shallow groundwater and the deep groundwater is separated at a depth of about 40 m, with substantial differences in terms of hydrochemical and isotopic characteristics. The results are useful for decision making related to sustainable water resource utilization in the Turpan Basin and other regions in northwestern China.     

Landscape eco-environment risk assessment of highway in arid area of Xinjiang, China

With the aid of analyses to landscape ecology in the highway region of the arid area in Xinjiang of China, vegetation type, soil type and land-use type were ascertained as environmental factors of highway landscape ecosystem fragility, and seasonal flood, blown-wind sand and alkali-salinization as disaster factors of highway engineering. All items of these factors constitute an objective hierarchy of evaluating landscape ecosystem risk of the highway region in the arid area. The weighted values of the items were determined according to the number of occupied area or length by them against each unit. The area or length was interpreted with the aids of GIS technology and gained by measuring in the highway reconnaissance. The results of the eco-environmental risk assessment of G315 Yitunbulake-Qiemo section in Xinjiang shows that eight units of landscape ecology can be sorted into four categories according to the differences of the fragility indices (Σxiwi) and the disaster indices (Σyiwj).     

Dry/wet climate zoning and delimitation of arid areas of Northwest China based on a data-driven fashion

The division of arid areas is important in water and land resources management, planning and for a long-term agricultural, economic and social planning. Northwest China(NW) dominates the main arid areas in China. There is thus a need to adopt adequate concepts relative to the scope of arid areas of NW China and identify its climate types and characteristics. In this study, we analyzed climatic data over the last 30 years(1981–2010) from 191 stations in three provinces and three autonomous regions of NW China. The factor-cluster analysis tech- nique(FC), an objective and automated method was employed to classify the dry/wet climate zones. The traditional methods with predefined thresholds were adopted for providing a comparison with FC. The results showed that the wet/dry climate zones by FC were mainly distributed along mountains, rivers and desert borders. Climate-division boundaries relied heavily on the major terrain features surrounding the grouped stations. It also showed that the climate was dry in the plain sandy areas but relatively wet in the high mountain areas. FC method can reflect the climate characteristics more fully in NW China with varied and complicated topography, and outperform the tradi- tional climate classifications. Arid areas of NW China were defined as four climate types, including five resultant classes in FC classifications. The Qinling and Da Hinggan Mountains were two important boundaries, besides main administrative boundaries. The results also indicated that there are some differences between two traditional clas- sifications. The precipitation moved and fluctuated to an extent, which confirmed that climate change played an important role in the dry/wet climate zoning, and the boundaries of dry/wet climate zones might change and migrate with time. This paper is expected to provide a more in-depth understanding on the climate characteristics in arid areas of NW China, and then contribute to formulate reasonable water and land management planning and agri- cultural production programs.     

Spatiotemporal variation of land surface temperature and its driving factors in Xinjiang,China

Land surface temperature(LST) directly affects the energy balance of terrestrial surface systems and impacts regional resources, ecosystem evolution, and ecosystem structures. Xinjiang Uygur Autonomous Region is located at the arid Northwest China and is extremely sensitive to climate change. There is an urgent need to understand the distribution patterns of LST in this area and quantitatively measure the nature and intensity of the impacts of the major driving factors from a spatial perspective...     

The qanats of Xinjiang:historical development, characteristics and modern implications for environmental protection

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.     

Modeling and analyzing supply-demand relationships of water resources in Xinjiang from a perspective of ecosystem services

Water shortage is one bottleneck that limits economic and social developments in arid and semi-arid areas.As the impacts of climate change and human disturbance intensify across time,uncertainties in both water resource supplies and demands increase in arid and semi-arid areas.Taking a typical arid region in China,Xinjiang Uygur Autonomous Region,as an example,water yield depth(WYD)and water utilization depth(WUD)from 2002 to 2018 were simulated using the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model and socioeconomic data.The supply-demand relationships of water resources were analyzed using the ecosystem service indices including water supply-demand difference(WSDD)and water supply rate(WSR).The internal factors in changes of WYD and WUD were explored using the controlled variable method.The results show that the supplydemand relationships of water resources in Xinjiang were in a slight deficit,but the deficit was alleviated due to increased precipitation and decreased WUD of irrigation.WYD generally experienced an increasing trend,and significant increase mainly occurred in the oasis areas surrounding both the Junggar Basin and Tarim Basin.WUD had a downward trend with a decline of 20.70%,especially in oasis areas.Water resources in most areas of Xinjiang were fully utilized and the utilization efficiency of water resources increased.The water yield module in the InVEST model was calibrated and validated using gauging station data in Xinjiang,and the result shows that the use of satellite-based water storage data helped to decrease the bias error of the InVEST model by 0.69×10⁸m³.This study analyzed water resource supplies and demands from a perspective of ecosystem services,which expanded the scope of the application of ecosystem services and increased the research perspective of water resource evaluation.The results could provide guidance for water resource management such as spatial allocation and structural optimization of water resources in arid and semi-arid areas.     

A preliminary study of water use strategy of desert plants in Dunhuang,China

Water is a restrictive factor for plant growth and ecosystem stability in arid and semiarid areas. The dynamics of water availability in soils and water use by plants are consequently critical to ecosystem functions, e.g. maintaining a high resistance to the changing climate. Plant water use strategies, including water-use efficiency(WUE) and the main water source that a plant species utilizes, play an important role in the evaluation of stability and sustainability of a plantation. The water use strategies of desert plants(Tamarix chinensis, Alhagi sparsifolia, Elaeagnus angustifolia, Sophora alopecuroides, Bassia dasyphylla and Nitraria sphaerocarpa) in three different habitats(saline land, sandy land and Gobi) in Dunhuang(located in the typical arid area of northwestern China) were studied. The stable isotope of oxygen was used to determine the main water source and leaf carbon isotope discrimination was used to estimate the long-term WUE of plant species in the summer of 2010. The results suggest that: 1) the studied desert plants took up soil water below the depth of 80 cm; 2) T. chinensis in the three habitats used deeper soil water and T. chinensis in the Gobi site had higher WUE than those in the saline land and the sandy land. The results indicated that desert plants in Dunhuang depended on stable water source and maintained high WUE to survive in water limited environments.     

Spatial-temporal characteristics and influencing factors of relative humidity in arid region of Northwest China during 1966–2017

Playing an important role in global warming and plant growth, relative humidity(RH) has profound impacts on production and living, and can be used as an integrated indicator for evaluating the wet-dry conditions in the arid and semi-arid area. However, information on the spatial-temporal variation and the influencing factors of RH in these regions is still limited. This study attempted to use daily meteorological data during 1966–2017 to reveal the spatial-temporal characteristics of RH in the arid region of Northwest China through rotated empirical orthogonal function and statistical analysis method, and the path analysis was used to clarify the impact of temperature(T), precipitation(P), actual evapotranspiration(ETa), wind speed(W) and sunshine duration(S) on RH. The results demonstrated that climatic conditions in North Xinjiang(NXJ) was more humid than those in Hexi Corridor(HXC) and South Xinjiang(SXJ). RH had a less significant downtrend in NXJ than that in HXC, but an increasingly rising trend was observed in SXJ during the last five decades, implying that HXC and NXJ were under the process of droughts, while SXJ was getting wetter. There was a turning point for the trend of RH in Xinjiang, which occurred in 2000. Path analysis indicated that RH was negatively correlated to T, ETa, W and S, but it increased with increase of P. S, T and W had the greatest direct effects on RH in HXC, NXJ and SXJ, respectively. ETa was the factor which had the greatest indirect effect on RH in HXC and NXJ, while T was the dominant factor in SXJ.     

Carbon storage in a wolfberry plantation chronosequence established on a secondary saline land in an arid irrigated area of Gansu Province,China

Carbon(C) storage has received significant attention for its relevance to agricultural security and climate change. Afforestation can increase C storage in terrestrial ecosystems, and has been recognized as an important measure to offset CO_2 emissions. In order to analyze the C benefits of planting wolfberry(Lycium barbarum L.) on the secondary saline lands in arid areas, we conducted a case study on the dynamics of biomass carbon(BC) storage and soil organic carbon(SOC) storage in different-aged wolfberry plantations(4-, 7-and 11-year-old) established on a secondary saline land as well as on the influence of wolfberry plantations on C storage in the plant-soil system in an arid irrigated area(Jingtai County) of Gansu Province, China. The C sequestration and its potential in the wolfberry plantations of Gansu Province were also evaluated. An intact secondary saline land was selected as control. Results show that wolfberry planting could decrease soil salinity, and increase BC, SOC and litter C storage of the secondary saline land significantly, especially in the first 4 years after planting. The aboveground and belowground BC storage values in the intact secondary saline land(control) accounted for only 1.0% and 1.2% of those in the wolfberry plantations, respectively. Compared to the intact secondary saline land, the SOC storage values in the 4-, 7-and 11-year-old wolfberry plantations increased by 36.4%, 37.3% and 43.3%, respectively, and the SOC storage in the wolfberry plantations occupied more than 92% of the ecosystem C storage. The average BC and SOC sequestration rates of the wolfberry plantations for the age group of 0–11 years were 0.73 and 3.30 Mg C/(hm~2·a), respectively. There were no significant difference in BC and SOC storage between the 7-year-old and 11-year-old wolfberry plantations, which may be due in part to the large amounts of C offtakes in new branches and fruits. In Gansu Province, the C storage in the wolfberry plantations has reached up to 3.574 Tg in 2013, and the C sequestration potential of the existing wolfberry plantations was 0.134 Tg C/a. These results indicate that wolfberry planting is an ideal agricultural model to restore the degraded saline lands and increase the C sequestration capacity of agricultural lands in arid areas.     

ON THE COMPREHENSIVE DEVELOPMENT AND UTILIZATION OF THE AGRICULTURAL RESOURCES IN YANCHI COUNTY——A TYPICAL TRANSITIONAL BELT BETWEN AGRICULTURE AND ANIMAL HUSBANDRY

<正> 1. The natural economic conditions of yanchi county Yanchi County (in Ningxia Province, China) lies between the Muwus Desert and theLoess Plateau, its geographical location is a typical transition belt. The view from south tonorth: the general configuration of the earth's surface is from the Loess Plateau to Ordos ta-bleland; the climate is from semi arid to arid. The transition of its geogrophical location pro-vides the area such features which are various,complex and fragile in natural conditions.     

Heterogeneity and non-linearity of ecosystem responses to climate change in the Qilian Mountains National Park,China

Ecosystem responses to climate change, particularly in arid environments, is an understudied topic. This study conducted a spatial analysis of ecosystem responses to short-term variability in temperature, precipitation, and solar radiation in the Qilian Mountains National Park, an arid mountainous region in Northwest China. We collected precipitation and temperature data from the National Science and Technology Infrastructure Platform, solar radiation data from the China Meteorological Forcing D...     

LAND RESOURCE CHARACTERISTICS AND RATIONAL LAND-USE ARRANGEMENT FOR FARMING,FORESTRY AND ANIMAL HUSBANDRY IN “THREE NORTHS” SHELTER FOREST AREA

<正> The "Three Norths" (Northeastern China, Northern China, and Northwestern China)Shelter forest area is located in the north part of china. The area of this region occupies41% of the total area of China. This region is eager for being managed because of its fragileecological conditions. Therefore, the basic approach to realize the harmonious developmentof ecological and economic benefits is the rational arrangement of farming, forestry and pas-ure land according to the characteristics of land resources of this region.