Land-Air Interaction over Arid/Semi-arid Areas in China and Its Impact on the East Asian Summer Monsoon. Part I:Calibration of the Land Surface Model (BATS)Using Multicriteria Methods

To improve the land surface simulation in the arid and semi-arid areas of northern China, the observational data from two field experiments in Dunhuang and Tongyu are used to optimize the parameters in the land surface model, BATS, through calibration with the multicriteria method. Sensitivity analysis to the parameters in Dunhuang and Tongyu indicates that different parameters need to be calibrated in two sites with different environmental and climate regimes. Comparison of observed sensible heat flux, latent heat flux, and ground surface temperature with the simulated ones shows the simulations with the optimized parameters have been substantially improved. Especially, the holistic simulations with the calibration of the parameter values are much closer to the observations in the arid region （Dunhuang）, and the energy partition with the calibrated parameters can also be simulated well in the semi-arid region （Tongyu）. Whole results demonstrate that the parameter calibration of the land surface model is important when the model is to be used to investigate the land-air interaction.

The causes of land landscape changes in semi-arid area of Northwest China: a case study of Yulin city

Rapid land landscape change has taken place in many arid and semi-arid regions such as the vulnerable ecological area over the last decade. In this paper, we quantified land landscape change of Yulin in this area between 1985 and 2000 using remote sensing and GIS. It was found that fallow landscape decreased by 125,148 hm^2 while grassland and woodland increased by 107,975 hm^2 and 17,157 hm^2, respectively. The major factors responsible for these changes are identified as the change in the government policy on preserving the environment, continued growth in mining, and urbanization. The efforts in restoring the deteriorated ecosystem have reaped certain benefits in reducing the spatial extent of sandy land through replacement by non-irrigated farmland, woodland and grassland. On the other hand, continued expansion of mining industry and urbanization has exerted adverse impacts on the land landscape. At present regional economic development conflicts directly with the protection of the natural environment. Such a conflict has caused the destruction to the land resources and fragmentation of the landscape accompanied by land desertification, the case is even serious in some localities.

LAND DEGRADATION AND ITS MANAGEMENT IN THE ARID AND SEMI ARID AREAS OF CHINA

hina is a large country with varied physical environments. Some of them are quite fragile and susceptible to land degradation, such as the arid and semiarid areas, as well as the slopeland of extensive mountain and hilly areas. Therefore, human actions play a significant role in desertification processes. It was estimated that there are 3,327,000 km 2 of desertified areas in China, in which 1,533,000 km 2 are desert, gobi and sandy desertified areas. Most of them are in arid, semiarid and dry sub humid areas in northern China. Soil salinization is another kind of land desertification. It was estimated that about one fifth of the 66,700 km 2 of farmlands have been affected by soil salinization to certain extent. Grassland degradation is also serious in China. The main problems are the reduction of bio mass, decline of preferred species and soil erosion induced by overgrazing. In Inner Mongolia the area of degraded grasslands occupies 43.8 percent of the total available area of the grasslands. The productivity of grasslands in Tibet has decreased by 20 - 50 percent [21]. Soil and water erosion is more serious in China. Based on remote sensing general survey initiated by Ministry of Water Resources in 1992, the total soil eroded area is 3,670,000 km 2, occupying 38.2 percent of the total territorial area, in which 1,790,000 km 2 is water eroded area and 1,880,000 km 2 is wind eroded area.

Remote Sensing Parameterization of Land Surface Heat Fluxes over Arid and Semi-arid Areas

Dealing with the regional land surfaces heat fluxes over inhomogeneous land surfaces in arid and semi-arid areas is an important but not an easy issue. In this study, one parameterization method based on satellite remote sensing and field observations is proposed and tested for deriving the regional land surface heat fluxes over inhomogeneous landscapes. As a case study, the method is applied to the Dunhuang experimental area and the HEIFE (Heihe River Field Experiment, 1988-1994) area. The Dunhuang area is selected as a basic experimental area for the Chinese National Key Programme for Developing Basic Sciences: Research on the Formation Mechanism and Prediction Theory of Severe Climate Disaster in China (G1998040900, 1999-2003). The four scenes of Landsat TM data used in this study are 3 June 2000, 22 August 2000, and 29 January 2001 for the Dunhuang area and 9 July 1991 for the HEIFE area. The regional distributions of land surface variables, vegetation variables, and heat fluxes over inhomogeneous landscapes in arid and semi-arid areas are obtained in this study.

Effects of Land Use Change on Ecosystem Services in Arid Area Ecological Migration

Ecological migration is the process of increasing the population density in the immigration area and transferring the ecological pressure from emigration area to immigration area. This process may result in significant changes in land use and land cover in the area of immigration and have an important effect on ecosystem services. Therefore, scientifically revealing the effects and differentiation mechanisms of ecological migration on ecosystem services is becoming an important issue related to the implementation of the national ecological migration strategy in China. This study employed the Hongsibu District as a typical example of ecological migration. Hongsibu District is located in the central Ningxia steppe and desert steppe areas. Remote sensing data covering five periods from the period before ecological migration in 1995 and after migration in 2000, 2005, 2010, and 2015 was used to measure the value of ecosystem services(ESV). A geographical detector model and the value of ecosystem services model were used to diagnose the dynamic mechanism of the effects of land use change on ecosystem services. The results showed that: 1) The development of large-scale ecological resettlement has caused the area of cultivated land and urbanized land area to increase significantly in the area of immigration, while the grass area decreased significantly. 2) The overall value of the Hongsibu ecosystem services increased in a form of a ‘V'. Among them, during the period of 1995–2005, the overall ESV decreased and had an annual rate of change of-0.67%. During the period of development 2005–2015, the ESV increased steadily, with an annual rate of change of 0.79%. 3) The proportion and total ESV in soil formation and protection, waste treatment, and biodiversity conservation of the Hongsibu District decreased from 57.61% in 1995 to 56.17% in 2015, indicating that the region's ecological regulation function slightly decreased. 4) The ESV in the Hongsibu District, showed a low distribution pattern of ecosystem services increasing from northeast to southwest, and the capacity of three townships, Hongsibu, Taiyangshan, and Liuquan, to provide ecosystem services gradually declined over time. The ecological service function of Xinzhuangji Township and Dahe Township gradually improved. 5) The sensitivity index of the ESV of each land use type was less than 1, indicating that the environment lacks flexibility in providing a strong ESV index in Hongsibu, which shows that the research results are reliable and believable. 6) During the study period, the decisive force of the change of land use on ecosystem services in Hongsibu District was: grassland(0.9934), climate regulation(0.9413), soil formation and protection(0.9321) and waste treatment(0.9241).

Foliar δ^13C Values and Water Use Efficiency ofSemi-arid Plants in Horqin Sandy Land, China

Water was a key factor restricting the plantation in sandy areas. Foliar δ^(13)C value regarded as an indicator of longterm water use efficiency(WUE) of plants was generally used to evaluate the adaptability of plants to arid and semi-arid environment. In Horqin sandy land of China, the foliar δ^(13)C values of 114 species in 35 families naturally growing in the area, and 15 species of sand-fixing trees and shrubs were measured and analyzed in 2012. The results showed that 97 species in all 114 species were C_3 plants and only 17 species were C_4 plants. Most C_4 plants belonged to Gramineae family. The foliar δ^(13)C value of C_3 plants was between -25.000 and -31.075‰ with an average of-28.226‰, while those of C_4 plants between -12.578 and -16.334‰, with an average of -13.678‰. The δ^(13)C values of mature leaves collected in August were averagely 0.85‰ less than that of juvenile leaves collected in June. The foliar δ^(13)C values and WUE of 15 sand-fixing tree species in Horqin sandy land ranked in the order as: S.vulgaris >H.rhamnoides >C.ovata >P.mongolica >T.chinensis >R.typhina >S.matsudana >E.angustifolia >U.pumila >S.gordejevii >X.sorbifolia >C.microphylla >H.fruticosum >C.korshinskii >E.bungeanus.

Spatial heterogeneity of plant species on the windward slope of active sand dunes in a semi-arid region of China

Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size （i.e. size of the sampling unit）, and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 mx50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with in- creasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness in- creased significantly. With the increase in sampling area, species abundance increased linearly, but richness in- creased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in sand dune fields.

Changes in soil organic carbon and nitrogen after 26 years of farmland management on the Loess Plateau of China

Soil carbon（C） and nitrogen（N） play a crucial role in determining the soil and environmental quality. In this study, we investigated the effects of 26 years（from 1984 to 2010） of farmland management on soil organic carbon（SOC） and soil N in abandoned, wheat（Triticum aestivum L.） non-fertilized, wheat fertilized（mineral fertilizer and organic manure） and alfalfa（Medicago Sativa L.） non-fertilized treatments in a semi-arid region of the Loess Plateau, China. Our results showed that SOC and soil total N contents in the 0–20 cm soil layer increased by 4.29（24.4%） and 1.39 Mg/hm2（100%）, respectively, after the conversion of farmland to alfalfa land. Compared to the wheat non-fertilized treatment, SOC and soil total N contents in the 0–20 cm soil layer increased by 4.64（26.4%） and 1.18 Mg/hm2（85.5%）, respectively, in the wheat fertilized treatment. In addition, we found that the extents of changes in SOC, soil total N and mineral N depended on soil depth were greater in the upper soil layer（0–30 cm） than in the deeper soil layer（30–100 cm） in the alfalfa land or fertilizer-applied wheat land. Fertilizer applied to winter wheat could increase the accumulation rates of SOC and soil total N. SOC concentration had a significant positive correlation with soil total N concentration. Therefore, this study suggested that farmland management, e.g. the conversion of farmland to alfalfa forage land and fertilizer application, could promote the sequestrations of C and N in soils in semi-arid regions.

REMOTE SENEING APPLICATION IN COUNTY-LEVEL LAND CLASSIFICATION AND LAND EVALUATION IN ARID AND SEMI-ARID ZONES——SHENMU COUNTY,SHAANXI PROVINCE AS A CASE STUDY

1. Backgrounds Land classification and evaluation are necessary foundments for county-level deci-sions of land use planning and economic development. On the bases of physical conditions,the targets of land classification and land evaluation adhere to particular principles andmethodologies are to find out the quality, quantity and spatial distribution regularities of re-gional structure of land, and to obtain relevant information of land suitabilities and

Surface Regional Heat(Cool) Island Effect and Its Diurnal Differences in Arid and Semiarid Resource-based Urban Agglomerations

With the rapid development of urban agglomerations in northwest arid and semiarid regions of China, the scope of the urban heat island(UHI) effect has gradually expanded and gradually connected, and has formed a regional heat island(RHI) with a larger range of impact to the regional environment. However, there are few studies on the heat island effect of urban agglomerations in arid and semiarid regions, so this paper selects the urban agglomeration of Hohhot, Baotou and Ordos(HBO) of Inner Mongolia, China as the study area. Based on the 8-day composite Moderate-resolution Imaging Spectroradiometer(MODIS) surface temperature data(156scenes in all) and land use maps for 2005, 2010, and 2015, we analyze the spatiotemporal distributions of regional heat(cool) islands(RH(C)I) and the responses of surface temperatures to land-use changes in the diurnal and interannual surface cities. The results showed that: 1) from 2005 to 2015, urban areas showed the cold island effect during the day, with the area of the cold island showing a shrinking feature;at night, they showed the heat island effect, with the area of the heat island showing a first decrease and then an increase.2) From 2005 to 2015, the land development(unutilized land to building land) brings the greatest temperature increase(ΔT = 1.36°C)during the day, while the greatest temperature change at night corresponds to the conversion of cultivated land to building land(ΔT =0.78°C) exhibited the largest changes at night. From 2010 to 2015, the land development(grassland to building land) bring the greatest temperature increase(ΔT = 0.85°C) during the day, while the great temperature change at night corresponds to the conversion of water areas to building land(ΔT = 1.38°C) exhibited the largest changes at night. Exploring the spatial and temporal evolution of surface urban heat(cool) islands in urban agglomerations in arid and semiarid regions will help to understand the urbanization characteristics of urban agglomerations and provide a reference for the formulation of policies for the coordinated and healthy development of the region and co-governance of regional environmental problems.

Applications of Soil Series in Sustainable Land Use of Oasis Farmlands

The issue of agricultural land sustainability is important to every part of the world, especially in the developing countries. Based on the data collected by field investigation and laboratory analysis as well as soil classification theory, the authors discuss the applications of soil series in the arid northwestern China. On the one hand, the application in the layout of rational agricultural of oasis farmlands: (1) two soil series,namely,Lanjiabao (main) and Nijiaxiaying, belong to the moderate and extremely arid region in the study area; accordingly, the layout of crops is the spring wheat and maize (main) and winter wheat;(2) Nijiaxiaying (main) and Lanjiabao, however, fall into the warm-cold and extremely arid region, where the winter wheat (main) and spring wheat grow; and (3) the Shangfusi is part of the warm chilly-arid region, which is used as seasonal pastureland. On the other hand, the application on the soil quality of oasis farmlands, the results indicating that among all soil series, the content of N is very low, however, the content of K is abundant, and the content of P is greatly scarce.

Soil Moisture Effects on Sand Saltation and Dust Emission Observed over the Horqin Sandy Land Area in China

In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity initiating the motion of surface particles, namely, the threshold friction velocity, is estimated to be 0.34, 0.40, and 0.50 m s？1 under the very dry, dry, and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission fl ux during the wet event is smaller, but the saltation activities of sand particles （d≧50 μm） are stronger. The size distributions of airborne dust particles （0.1≦d≦20 μm） show that concentrations of the fi ner dust particles （0.1≦d≦0.3 μm） have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have a larger size, and hence more potential saltating particles are available. This explains the occurrence of stronger saltation processes observed under wet soil conditions.

The Change of Land Use/Cover and Characteristics of Landscape Pattern in Arid Areas Oasis： An Application in Jinghe, Xinjiang

This paper uses 3S technology in macroscopic. Combining the integrated technology of ecological quantity analytical method with GIS technology through ArcGIS and Fragstats, the authors study the images of 1972, 1990, 2001, and 2005 and obtained land use data in Jinghe County. Then, the change of land use/cover and landscape pattern had been analyzed in the Jinghe County of Xinjiang. The conclusions were as follows: (1) The trend of LUCC is that the area of oasis expands slowly in nearly 33 years between 1972 to 2005 in Jinghe County. (2) The water area is mainly influenced by Ebinur Lake, so the area expands a little in this period. (3) The area of salinization-land expands at first and reduces later. The area of sand land decreases and the other land class increases, while the probability of transfer is always high. (4) Landscape change is also obvious throughout the decades. Overall, landscape density increases, the largest path index decreases at first and expends later, the weight area index decreases, and the shape of landscape becomes regulated. The nearest distances, the degrees of reunite, and outspread decreases. It shows that the connection of the main path in 1972 is better than 2005, wherein the patch becomes more complex. From the changes of Shannon’s Diversity Index and Shannon’s Evenness Index, we know that the diversity of landscape and the Interspersion Juxtaposition Index increase. The degree of diversity landscape and fragmentation increase also shows that the land uses become more complex. All in all, it is essential to intensify the spatial relationships among landscape elements and to maintain the continuity of landscape ecological process and pattern in the course of area expansion.

The classification and assessment of vulnerability of man-land system of oasis city in arid area

Oasis city system is the center of the man-land relationship in arid area and it is the most influential spatial and temporal multiple dynamic system. Oasis city system is not only the largest area where artificial disturbances occur at a regional scale but also the most concentrated area of human activity in arid area. In this study, we developed an applicable and convenient method to assess vulnerability of man-land system of oasis cities with vulnerability indicator system, respectively evaluating the sensitivity, adaptability and vulnerability of the eco- environment system, the economic system and the social system. The results showed that the sensitivity and vulnerability of oasis cities in Xinjiang, China have significant differences while their adaptability does little. In order to find the inherent differences in the vulnerability of oasis cities, triangle methodology has been adopted to divide Xinjiang oasis cities into five types. Some adaptive developing policies specific for individual cities are also proposed based on their vulnerability type and constrain- ing factors.

SOME NEW UNDERSTANDINGS OF LAND-SURFACE PROCESSES IN ARID AREA FROM THE HEIFE

The survey for the HEIFE(Atmosphere-Land Surface Processes Experiment at Heihe River Basin,Western China)is given in the paper.The following basic subjects for land-surface process- es in arid areas are studied:(1)the general characteristics of the energy budget on ground surface in arid areas;(2)the parameterization of the land surface processes;(3)the interaction between oasis and its desert circumstances,a special phenomenon in arid areas.The analysis shows that the sensible heat flux in the surface energy budget is in the majority,and the latent heat flux may be neglected.The influence of atmospheric stratification stability on the turbulent transfer of energy and substance must be considered in parameterization of land surface processes in arid areas.The “cold island effect”phenomenon in oasis and the“humidity inversion”phenomenon in desert near oasis are the result of the interaction between them.The results would improve the understanding of land surface processes in arid areas.

Deep soil water infiltration and its dynamic variation in the shifting sandy land of typical deserts in China

Soil moisture is the key resource constraint in arid ecosystems, and has been a focus of research on restoration. However, quantitative studies on the contribution of rainfall to deep soil rainfall infiltration are lacking. In this study, we used the YWB-01 Deep Soil Infiltration Water Recorder which had been invented by ourselves to measure the quantity of rain infiltration into deep soil, 150 cm below ground, in four locations in China: Mu Us Sandy Land and Ulan Buh, Tengger, and Badan Jilin deserts over a 2-year period. We found:(1) Deep soil rainfall infiltration decreased progressively from east to west and from semiarid to arid areas, with two locations completely lacking rainfall infiltration. Heavy rain was important to deep soil infiltration in shifting sandy land of arid and semiarid areas.(2) Seasonal variation of infiltration was correlated with rainfall, with a time lag that was less apparent in areas with more rainfall.(3) For single intense rainfall events, infiltration maximums occurred 40–55 h after the rainfall, during which the infiltration rates increased rapidly before reaching a peak, and then decreased slowly. Continuous infiltration could last about 150 h. Rainfall infiltration was determined by the combined action of intensity, quantity and duration. Rainfall with low intensity, long duration, and large quantity was most favorable for deep soil infiltration. Our results can be used in water resource assessments and protection during eco-restoration in the arid and semiarid areas in China.

Comparison Between the Formation of Peatlands and Paleosols of Sandy Land and the Changes of Ari4 Index During Holocene in Northeast China

In Northeast China, peatlands and paleosols have developed very well in the eastern swamps and western sandy lands, respectively. They become an important object of studying the paleoenvironment in this region. Since both of them were formed under humid climate conditions, it is significant to compare their formation and ages for the unification of climatic change divisions and the reconstruction of the

Leaf traits and their interrelationship of 23 plant species in southeast of Keerqin Sandy Lands,China

Six leaf traits,i.e.,fresh mass(FM),dry mass(DM),leaf dry matter content(DMC),area(AR),specific leaf area(SLA)and thickness(TH)from 23 plant species in the southeastern Keerqin Sandy Lands,China were measured.The results show that leaf traits of herbs were more diversified than those of shrubs and trees and aver-age SLA tended towards a decreasing trend from herbs to shrubs to trees.On the contrary,DMC and DM show an upward trend from herbs to shrubs to trees.No apparent difference was found in TH.Except for DM and TH,there were significant variations in SLA and DMC among three different growth forms.Moreover,a significant correlation was found between SLA and DMC.It is concluded that SLA and DMC could be used to predict species position along a resource use gradient.

干旱风沙区不同林龄柠条锦鸡儿水分利用特征研究

【目的】探明干旱风沙区老龄、中龄和幼龄柠条在干旱严苛环境条件下的用水策略,对当地生态环境保护与可持续发展提供理论依据。【方法】采用稳定同位素技术,通过测定柠条可利用的水源和枝条木质部水分的同位素特征比率,应用IsoSource模型对比研究不同林龄人工柠条林主要利用水分来源及各水源的贡献率,并结合土壤水分的补给特征,综合分析人工柠条林对干旱严苛环境的适应机制。【结果】在整个生长季,3种林龄柠条在0~40 cm浅土层土壤含水量较为波动,在160~200 cm深土层柠条土壤含水量较为稳定。不同林龄柠条0~200 cm土层平均土壤含水量为建植20年>建植8年>建植4年。不同林龄柠条各土层水分贡献率均不同,建植20年的柠条主要利用土层80~120 cm的土壤水分,贡献率为49.5%;建植8年的柠条主要利用0~20 cm和80~120 cm土层土壤水分,贡献率分别为59.2%和14.8%;建植4年的柠条主要利用土层0~20 cm的土壤水分,贡献率达85.7%。【结论】不同林龄柠条用水策略与各土层土壤含水量的高低有直接关系。土层土壤含水量高低决定各土层水分贡献率的大小。老龄柠条主要利用深层土壤水分,中龄柠条主要利用浅层和中层土壤水分,幼龄柠条主要利用浅层土壤水分。

宁夏干旱风沙区不同季节柠条锦鸡儿水分利用特征研究

柠条锦鸡儿是宁夏干旱风沙区生态重建的主要树种,为明确宁夏干旱风沙区不同季节柠条锦鸡儿在干旱严苛环境条件下的用水策略,该研究采用稳定同位素技术,通过测定柠条锦鸡儿可利用的水源和枝条木质部水分的同位素特征比率,应用IsoSource模型,从定性和定量角度出发,对比研究不同季节柠条锦鸡儿主要利用水分来源及各水源的贡献率,同时结合土壤水分的补给特征,综合分析柠条锦鸡儿应对干旱严苛环境的适应机制。结果表明:在0~60 cm土层,不同季节柠条锦鸡儿土壤含水量差异显著,雨季的土壤含水量均值为14.66%,而旱季的土壤含水量仅为9.69%。在80~200 cm土层,不同季节柠条锦鸡儿土壤含水量差异不显著。不同季节柠条锦鸡儿各水分来源贡献率均不同。在雨季,雨水的贡献率高达93.00%,而土壤水分贡献率仅为7.00%。在旱季,80~200 cm土层的土壤水,水分贡献率达到64.10%,0~60 cm土层土壤水分有部分利用。可见,一定降雨事件影响浅层土壤水分含量,对深层土壤水分影响不显著。不同季节柠条用水策略与各土层土壤含水量的高低有直接关系。雨季,柠条锦鸡儿利用雨水;旱季,柠条锦鸡儿主要利用深层土壤水分,对浅层水分也有一定利用。柠条锦鸡儿在不同季节能通过转化不同水源利用来应对干旱严苛的环境,从而维持自身生长。