Oasis Area Research Articles

A decision-making framework to model environmental flow requirements in oasis areas using Bayesian networks

The competition for water resources between agricultural and natural oasis ecosystems has become an increasingly serious problem in oasis areas worldwide. Recently, the intensive extension of oasis farmland has led to excessive exploitation of water discharge, and consequently has resulted in a lack of water supply in natural oasis. To coordinate the conflicts, this paper provides a decision-making framework for modeling environmental flows in oasis areas using Bayesian networks (BNs). Three components are included in the framework: (1) assessment of agricultural economic loss due to meeting environmental flow requirements; (2) decision-making analysis using BNs; and (3) environmental flow decision-making under different water management scenarios. The decision-making criterion is determined based on intersection point analysis between the probability of large-level total agro-economic loss and the ratio of total to maximum agro-economic output by satisfying environmental flows. An application in the Qira oasis area of the Tarim Basin, Northwest China indicates that BNs can model environmental flow decision-making associated with agricultural economic loss effectively, as a powerful tool to coordinate water-use conflicts. In the case study, the environmental flow requirement is determined as 50.24%, 49.71% and 48.73% of the natural river flow in wet, normal and dry years, respectively. Without further agricultural economic loss, 1.93%, 0.66% and 0.43% of more river discharge can be allocated to eco-environmental water demands under the combined strategy in wet, normal and dry years, respectively. This work provides a valuable reference for environmental flow decision-making in any oasis area worldwide.

Rôles des petits ruminants dans l’amélioration des conditions de vie en milieu rural – Analyse comparative en Egypte

L’étude est centrée sur l’évaluation de la contribution de l’éle­vage de petits ruminants dans la réduction de la pauvreté et de la vulnérabilité des systèmes agricoles de trois zones agro­écologiques en Egypte : la zone pastorale du littoral Nord- Ouest (région de Matrouh), les zones irriguées de la vallée du Nil (région de Sohag) et les oasis du désert Ouest (région de la Nouvelle Vallée). Une étude empirique sur 90 exploitations dans les trois zones agroécologiques portant sur différents indicateurs économiques et sociaux liés à la pauvreté a donné des indications sur le rôle des ovins et des caprins dans dif­férents types d’exploitation, selon les dotations en ressources (en particulier terre, bétail, capital) et les ressources humaines. Les résultats ont montré que les petits ruminants constituaient la principale source de revenus des ménages pour échapper à la pauvreté, notamment pour les sans terre et les très petits propriétaires terriens. En outre, l’élevage était un capital qui générait d’autres richesses qui n’ont pas été prises en compte dans l’approche de la pauvreté monétaire.

Land use policy and spatiotemporal changes in the water area of an arid region

In this study, we developed a framework to analyze the impact of land use policies on water area changes. We used quantitative and qualitative approaches in our model, including Delphi method, Moran’s I, 3D kernel density surface (3D-KDS) technique, and orthogonalized regression. The model facilitates visual examination of spatiotemporal patterns in water area changes and identification of the net effect of land use policies on water area changes. We consider three types of land use policy and four control variables which include water management policy and climate change factors to test the model by using data from Ejina, an oasis area from Inner Mongolia, China. The results of both 3D-KDS and Moran’s I coefficient showed distinctive patterns in negative and positive water area changes. Standardized coefficients from the augmented orthogonalized ordinary least squares (OLS) models helped isolate the net effects of the three types of land use policy on negative and positive water area changes. Land use policies had greater impact on hydrological environment changes than water management policy and climate change factors. Our model can be utilized to assess the effectiveness of land use policies in an area and aid in helpful in monitoring the implementation of existing policies and design of new land use policies.

Phlebotomine sand flies (Diptera: Psychodidae) transmitting visceral leishmaniasis and their geographical distribution in China: a review.

After the existence of phlebotomine sand flies was first reported in China in 1910, the distribution of different species and their role in the transmission of visceral leishmaniasis (VL) have been extensively studied. Up until 2008, four species have been verified as vectors of VL, namely, Phlebotomus chinensis (Ph. sichuanensis), Ph. longiductus (Ph. chinensis longiductus), Ph. wui (Ph. major wui), and Ph. alexandri.The sand fly species vary greatly depending on the natural environments in the different geographic areas where they are endemic. Ph. chinensis is euryecious and adaptable to different ecologies, and is thus distributed widely in the plain, mountainous, and Loess Plateau regions north of the Yangtze River. Ph. longiductus is mainly distributed in ancient oasis areas south of Mt. Tianshan in the Xinjiang Uygur autonomous region. Ph. wui is the predominant species in deserts with Populus diversifolia and Tamarix vegetation in Xinjiang and the western part of the Inner Mongolia autonomous region. Finally, Ph. alexandri is steroecious and found only in stony desert areas, such as at the foot of the mountains in Xinjiang and the western Hexi Corridor, in Gansu province. This review summarized the relationship between the geographic distribution pattern of the four sand fly species and their geographical landscape in order to foster research on disease distribution and sand fly control planning. Furthermore, some problems that remained to be solved about vectors of VL in China were discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0107-z) contains supplementary material, which is available to authorized users.

Hydrogeological and hydrogeochemical control of groundwater salinity in an arid inland basin: Dunhuang Basin, northwestern China

High groundwater salinity has become a major concern in the arid alluvial plain of the Dunhuang Basin in northwestern China because it poses a significant challenge to water resource management. Isotopic and geochemical analyses were conducted on 55 water samples from springs, boreholes and surface water to identify potential sources of groundwater salinity and analyse the processes that control increasing salinity. The total dissolved solid (TDS) content in the groundwater ranged from 400 to 41 000 mg/l, and high TDS values were commonly associated with shallow water tables and flow-through and discharge zones in unconfined aquifers. Various groundwater contributions from rainwater, agricultural irrigation, river water infiltration and lateral inflows from mountains were identified by major ions and δD and δ18O. In general, HCO3− and SO42− were the dominant anions in groundwater with a salinity of 2500 mg/l. The major ion concentrations indicated that mineral weathering, including carbonate and evaporite dissolution, primarily affected groundwater salinity in recharge areas. Evapotranspiration controlled the major ion concentration evolution and salinity distribution in the unconfined groundwaters in the flow-through and discharge areas, although it had a limited effect on groundwater in the recharge areas and confined aquifers. Agricultural irrigation increased the water table and enhanced evapotranspiration in the oasis areas of the basin. TDS and Cl became more concentrated, but H and O isotopes were not enriched in the irrigation district, indicating that transpiration dominated the increasing salinity. For other places in the basin, as indicated by TDS, Cl, δD and δ18O characteristics, evaporation, transpiration and water–rock interactions dominated at different hydrogeological zones, depending on the plant coverage and hydrogeological conditions. Groundwater ages of 3H, and δD and δ18O compositions and distributions suggest that most of the groundwaters in Dunhuang Basin have a paleometeoric origin and experienced a long residence time. These results can contribute to groundwater management and future water allocation programmes in the Dunhuang Basin. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of water and salinity on plant species composition and community succession in Ejina Desert Oasis, northwest China

Ecologic patterns and community succession are generally controlled by hydrologic mechanisms, especially for plant distributions which are sensitive to habitat conditions. The hydrology characteristics of ecosystems mainly influenced plant ecological processes in water and salinity changes. In this paper, we analyzed the composition and characteristic of natural plant community, divided the plant community classes and discussed the effect of water and salinity gradients on plant species and community classes in Ejina Desert Oasis. The results demonstrated that Populus euphratica, Tamarix chinensis and Phragmites communis were the most important plant species that had the highest important values among forest, shrubs and herbaceous. Six plant community patterns were classified by cluster analysis in Ejina Desert Oasis. Species richness and species diversity were the highest near West River and East River channels of the core oasis area. The distributions of plant community were mainly influenced by the following factors: distance from river channel, groundwater level, soil water content, soil salinity and groundwater salinity. The water and salinity factors, which controlled the distributions of plant, were the main driving forces for ecosystem succession. The plant community succession is becoming toward the type of shrub + herb or low shrub with very drought-tolerant from the type of forest + shrub + herb with tall and high water consumption, when habitat conditions change from good to poor. The water gradients had more significant and more directed effect than salinity gradients on plant species and communities.

Criterion definition for the identification of physical-geographical boundaries of Khorezm oasis through remotely sensed data.

The Khorezm oasis is one of the main ancient agricultural and cultural centers of Asia. Different studies have used administrative boundaries, without regard to the ecosystem complexity. Remote sensing is a technique that provides many advantages in relation to traditional land cover monitoring approaches. The main objective of this study was to identify the physical-geographical boundaries of Khorezm oasis and analyzed area change dynamics of the oasis using remote sensing data. Landsat 4-5 Thematic Mapper (TM) and Landsat 8 Operational Land Imager (OLI) images from 1998, 2010, and 2014 were used in order to identify the oasis boundaries by analyzing the normalized difference vegetation index (NDVI). The Landsat data were radiometric normalized before the NDVI estimation. Several NDVI cutoff values were tested in order to define the more adequate value to identify the oasis boundaries (NDVI ≥ 0.1 for 1998 and 2010 images and NDVI ≥ 0.2 for 2014 images). Geographical Information System (GIS) techniques were then used to calculate the oasis area (31,885.49, 30,005.58, and 28,966.08 km(2), for 1998, 2010, and 2014, respectively) and analyze the land cover changes. The oasis presents a total area loss of 2919.41 km(2) between 1998 and 2014. The mean percentage variations between 2010 and 1998 and from 2014 to 1998 were -5.9 and -9.2 %, respectively. Therefore, the Khorezm oasis lost more than 9 % of this area between 1998 and 2014. The main areas of decrease appeared in the southern parts of the Aral Sea where the last tributaries of the Amudarya River were located. This work allowed mapping the physical-geographical boundaries of Khorezm oasis and identifying its dynamics for the analyzed period. The methodology presented in this work can be applied to other oasis regions, located in different parts of the world.

Quantification of Environmental Flow Requirements to Support Ecosystem Services of Oasis Areas: A Case Study in Tarim Basin, Northwest China

Recently, a wide range of quantitative research on the identification of environmental flow requirements (EFRs) has been conducted. However, little focus is given to EFRs to maintain multiple ecosystem services in oasis areas. The present study quantifies the EFRs in oasis areas of Tarim Basin, Xinjiang, Northwest China on the basis of three ecosystem services: (1) maintenance of riverine ecosystem health, (2) assurance of the stability of oasis–desert ecotone and riparian (Tugai) forests, and (3) restoration of oasis–desert ecotone groundwater. The identified consumptive and non-consumptive water requirements are used to quantify and determine the EFRs in Qira oasis by employing the summation and compatibility rules (maximum principle). Results indicate that the annual maximum, medium, and minimum EFRs are 0.752 × 108, 0.619 × 108, and 0.516 × 108 m3, respectively, which account for 58.75%, 48.36%, and 40.29% of the natural river runoff. The months between April and October are identified as the most important periods to maintain the EFRs. Moreover, the water requirement for groundwater restoration of the oasis–desert ecotone accounts for a large proportion, representing 48.27%, 42.32%, and 37.03% of the total EFRs at maximum, medium, and minimum levels, respectively. Therefore, to allocate the integrated EFRs, focus should be placed on the water demand of the desert vegetation’s groundwater restoration, which is crucial for maintaining desert vegetation to prevent sandstorms and soil erosion. This work provides a reference to quantify the EFRs of oasis areas in arid regions.

Evapotranspiration Estimation for an Oasis Area in the Heihe River Basin Using Landsat-8 Images and the METRIC Model

The Heihe River Basin is the second largest inland river basin in arid northwestern China. Accurate estimation of regional evapotranspiration (ET) and its spatial distribution in the oasis area plays an important role for water resource management in the whole basin. The objective of this study was to estimate the temporal and spatial variations of ET for different land cover types in the oasis. To estimate ET values in the growing season of 2013, 14 Landsat-8 images of the study area were processed using the Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) model. A new approach selected hot extreme pixels separately for the desert and oasis sub-areas due to large differences in soil thermal characteristics. Results indicated large temporal-spatial variations in ET in the oasis. The largest ET values occurred over water bodies, followed by arable land, low-lying land and forest. The desert-oasis transition zones (shrubland, sparse forest, medium- and low-coverage grassland) had lower ET values, while the lowest ET values occurred in unused lands (salt meadows, sandy and Gobi deserts). Monthly ET values of all land cover types increased from April, peaked in July, before decreasing until October. Overall, METRIC can provide reasonable ET estimates in a heterogeneous land use types under advective environmental conditions with the selection of appropriate extreme pixels.

Land capability classification of some western desert Oases, Egypt, using remote sensing and GIS

Two desert Oases (i.e. Al-Kharga and Al-Dakhla), located in the western desert of Egypt, were selected as case studies. Soil, ETM+ satellite images, climatic and landscape database, were integrated through a GIS model. Digital Elevation Model (DEM) was elaborated using SRTM space images, in addition to spot heights and contour lines, derived from topographic maps. The created land resource database was used to evaluate and map land capabilities on bases of FAO (1985) methodology.The obtained data indicate that the highly capable soils represent 24.5% of Al-Kharga Oases and 19.2% of Al-Dakhla Oases. These soils are associated with the Typic Haplotorrerts and Typic Torrifluvents sub-great groups. The moderately capable soils represent 1.5% of the total area of Al-Kharga Oases and 6.1% of Al-Dakhla Oases. They were found to be associated with sub-great group soil Typic Torriorthents. The low capable soils represent 36.0% of Al-Kharga Oases total area and 20.3% of Al-Dakhla Oases; this class is associated with the soils of Torripsamments great group. The rest of the Oases are considered as non-capable soils or rock land, representing 38.0% of Al-Kharga Oases total area and 54.5% of Al-Dakhla Oases.It could be concluded that the desert Oases are sustainable areas, which might have potential importance supporting the national development programs. Integrating remote sensing data with digital soil map, using GIS, led to the elaboration of successful land capability classification mapping.

Ecological benefit of different revegetated covers in the middle of Hexi corridor, northwestern China

Desertification is one of the major obstacles to the development and utilization of oases in arid and semi-arid regions of China. Revegetation of oases is an effective means of protecting oases from sand invasion (the main cause of desertification) and enhancing the ecological stability of oasis. In order to assess the effects of revegetated plant communities, 21-year-old Haloxylon ammodendron shrubland (Shrubland), 28-year-old Populus simonii Carr. land (Poplar land) and 33-year-old Pinus sylvestris var. mongolica Litv land (Pine land) were selected as study objects. The topsoil properties and material changes were monitored, taking the native desert shrubland (Desert land) as a basis. The results show that different revegetated covers can lead to significant changes in soil organic carbon (SOC), as well as soil inorganic carbon (SIC) and total nitrogen (TN). SOC, SIC and TN content can be significantly increased from 0.56, 0.06, and 4.93 g kg−1 in Desert land to 5.85, 0.47, and 7.26 g kg−1 in revegetated covers, respectively. Different revegetated covers can also change plant species richness, productivity, and plant C and N content. It is also found that Poplar land and Pine land were more effective than Shrubland in improving soil fertility and plant productivity. In addition, this study confirmed that the establishment of revegetated covers can reduce the rates of wind erosion on soil surface up to 74.83–94.15 % compared to natural desert shrubland. The atmospheric dust fall was also affected significantly by the different covers. The results show that there are significant advantageous changes in soil characteristics and vegetation parameters, as well as the reduction of soil erosion and retention of atmospheric dust fall in the revegetated covers and habitat conditions. The results suggested the appreciable ecological effects of the different revegetation covers on soil development and restoration process of plant communities. Additionally, some rational management practices could also cause positive influence on the quality of soil, e.g. irrigation. Understanding these ecological effects may be helpful for designing and establishing protective forest systems in desert–oasis areas.

Development of a High Resolution BRDF/Albedo Product by Fusing Airborne CASI Reflectance with MODIS Daily Reflectance in the Oasis Area of the Heihe River Basin, China

A land-cover-based linear BRDF (bi-directional reflectance distribution function) unmixing (LLBU) algorithm based on the kernel-driven model is proposed to combine the compact airborne spectrographic imager (CASI) reflectance with the moderate resolution imaging spectroradiometer (MODIS) daily reflectance product to derive the BRDF/albedo of the two sensors simultaneously in the foci experimental area (FEA) of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER), which was carried out in the Heihe River basin, China. For each land cover type, an archetypal BRDF, which characterizes the shape of its anisotropic reflectance, is extracted by linearly unmixing from the MODIS reflectance with the assistance of a high-resolution classification map. The isotropic coefficients accounting for the differences within a class are derived from the CASI reflectance. The BRDF is finally determined by the archetypal BRDF and the corresponding isotropic coefficients. Direct comparisons of the cropland archetypal BRDF and CASI albedo with in situ measurements show good agreement. An indirect validation which compares retrieved BRDF/albedo with that of the MCD43A1 standard product issued by NASA and aggregated CASI albedo also suggests reasonable reliability. LLBU has potential to retrieve the high spatial resolution BRDF/albedo product for airborne and spaceborne sensors which have inadequate angular samplings. In addition, it can shorten the timescale for coarse spatial resolution product like MODIS.

Evolution of the human–water relationships in the Heihe River basin in the past 2000 years

Abstract. This paper quantitatively analyzed the evolution of human–water relationships in the Heihe River basin of northern China over the past 2000 years by reconstructing the catchment water balance by partitioning precipitation into evapotranspiration and runoff. The results provided the basis for investigating the impacts of societies on hydrological systems. Based on transition theory and the rates of changes of the population, human water consumption and the area of natural oases, the evolution of human–water relationships can be divided into four stages: predevelopment (206 BC–AD 1368), take-off (AD 1368–1949), acceleration (AD 1949–2000), and the start of a rebalancing between human and ecological needs (post AD 2000). Our analysis of the evolutionary process revealed that there were large differences in the rate and scale of changes and the period over which they occurred. The transition of the human–water relationship had no fixed pattern. This understanding of the dynamics of the human–water relationship will assist policy makers in identifying management practices that require improvement by understanding how today's problems were created in the past, which may lead to more sustainable catchment management in the future.

Using the Surface Temperature-Albedo Space to Separate Regional Soil and Vegetation Temperatures from ASTER Data

Soil and vegetation component temperatures in non-isothermal pixels encapsulate more physical meaning and are more applicable than composite temperatures. The component temperatures however are difficult to be obtained from thermal infrared (TIR) remote sensing data provided by single view angle observations. Here, we present a land surface temperature and albedo (T-α) space approach combined with the mono-surface energy balance (SEB-1S) model to derive soil and vegetation component temperatures. The T-α space can be established from visible and near infrared (VNIR) and TIR data provided by single view angle observations. This approach separates the soil and vegetation component temperatures from the remotely sensed composite temperatures by incorporating soil wetness iso-lines for defining equivalent soil temperatures; this allows vegetation temperatures to be extracted from the T-α space. This temperature separation methodology was applied to advanced scanning thermal emission and reflection radiometer (ASTER) VNIR and high spatial resolution TIR image data in an artificial oasis area during the entire growing season. Comparisons with ground measurements showed that the T-α space approach produced reliable soil and vegetation component temperatures in the study area. Low root mean square error (RMSE) values of 0.83 K for soil temperatures and 1.64 K for vegetation temperatures, respectively, were obtained, compared to component temperatures measurements from a ground-based thermal camera. These results support the use of soil wetness iso-lines to derive soil surface temperatures. It was also found that the estimated vegetation temperatures were extremely close to the near surface air temperature observations when the landscape is well watered under full vegetation cover. More robust soil and vegetation temperature estimates will improve estimates of soil evaporation and vegetation transpiration, leading to more reliable the monitoring of crop water stress and drought.

Diurnal and seasonal variations in carbon dioxide exchange in ecosystems in the Zhangye oasis area, Northwest China.

Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime Reco increases exponentially with air temperature. High Q10 values were observed when the vegetation coverage was relatively low, and low Q10 values occurred when the vegetables grew vigorously.

Hydrogeochemical and isotope evidence of groundwater evolution in El Guettar Oasis area, Southwest Tunisia

In southern Tunisia, the major aquifer system is characterized by the superposition of three principal levels: the upper unconfined Quaternary alluvial aquifer; the intermediate semi-confined/confined complex terminal (Segui, Beglia and Zebbag Formations) and the Continental intercalaire (Bou Dinar and Sidi Aich Formations) which constitutes the deeper confined aquifer. The hydrodynamic functioning of this aquifer system is largely influenced by tectonics (Gafsa and Sehib faults), lithologic variation and recharge conditions. The tectonics has contributed to the discontinuity of the aquifer levels by creating some barriers, which play the role of hydraulic sills. A study of the potentiometric maps shows four principal flow directions. These flow directions converge at the sill zones (Chott El Guettar and Chott Djerid depressions). The total mineralization evolution shows an increase from the periphery of the basin to the discharge area (1.75 ≤ TDS ≤ 14.4 g/l). Dissolution of halite, gypsum and/or anhydrite-bearing rocks is the principal source of the salinity of the groundwater. The isotopic signatures permit to classify the studied groundwaters into two different groups: Non-evaporated groundwaters that are characterized by depleted δ18O and δ2H contents highlight the importance of modern recharge at higher altitude. Evaporated groundwaters with enriched contents reflect the significance infiltration of return flow irrigation waters and the influence of the water dam. Tritium data in the studied groundwaters lend support to the existence of pre-1950 and post-1960 recharge. According to radiocarbon residence time estimates, the deep groundwater is approximately 40 kyears old, and was recharged during a period when the climate was wetter and colder. Based on radiocarbon content, the shallow groundwater is older than 0.5 kyear, and represents modern waters mixed with a limited quality of palaeo-recharge. Moreover, the insulation of certain compartments of the reservoir and inter-communications between the aquifer levels seem to play a principal role in the degradation of quality of groundwater.

1963—2009年金塔绿洲变化对绿洲景观格局的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 1963-2009年金塔绿洲变化对绿洲景观格局的影响 DOI: 10.5846/stxb201304080639 作者: 作者单位: 干旱环境与气候变化协同创新中心,干旱环境与气候变化协同创新中心,干旱环境与气候变化协同创新中心,干旱环境与气候变化协同创新中心,干旱环境与气候变化协同创新中心 作者简介: 通讯作者: 中图分类号: F301.24 基金项目: 中央高校基本科研业务费专项资金资助(lzujbky-2013-m02); 教育部"春晖计划"科研项目(Z2011028) Spatio-temporal change and its effects on landscape pattern of Jinta Oasis in Arid China from 1963 to 2009 Author: Affiliation: Collaborative Innovation Centre for Arid Environments and Climate Change CAEC,Key Laboratory of Western China’s Environmental Systems Ministry of Education,Lanzhou University,Collaborative Innovation Centre for Arid Environments and Climate Change CAEC,Key Laboratory of Western China’s Environmental Systems Ministry of Education,Lanzhou University,Collaborative Innovation Centre for Arid Environments and Climate Change CAEC,Key Laboratory of Western China’s Environmental Systems Ministry of Education,Lanzhou University,Collaborative Innovation Centre for Arid Environments and Climate Change CAEC,Key Laboratory of Western China’s Environmental Systems Ministry of Education,Lanzhou University,Collaborative Innovation Centre for Arid Environments and Climate Change CAEC,Key Laboratory of Western China’s Environmental Systems Ministry of Education,Lanzhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:内陆河流域绿洲与荒漠景观之间的相互作用与影响机制是干旱区景观地理学的重要内容之一。绿洲时空变化及其对区域景观格局影响的研究,对流域绿洲管理和环境保护具有重要的指导意义和科学价值。以中国西北干旱区内陆河流域水土资源开发的典型代表区域——金塔绿洲为例,基于5期不同的卫星遥感数据,利用数理统计模型及景观指数等方法开展绿洲变化过程、趋势、空间分布格局和景观结构特征变化研究。结果表明:(1)1963-2009年间金塔绿洲主要以扩张为主,绿洲面积增加了167.37 km2,绿洲与荒漠间相互转化剧烈,呈现出非平衡-平衡-极端不平衡的趋势状态。绿洲变化主要体现在西坝乡、羊井子湾乡的绿洲外延扩张和在三合乡-中东-大庄子乡、金塔镇-中东镇、古城乡等地的绿洲内部填充合并。(2)近46 a来金塔绿洲景观的分形特征、离散程度和破碎化程度趋于减小,各景观斑块则趋于简单和均匀化。(3)绿洲变化在一定程度上影响着绿洲景观格局,导致景观结构趋于均匀化和密集化,绿洲斑块镶嵌体表现出散布-扩张-破碎-融合扩展的变化过程。 Abstract:Oasis was a small and medium scale zonal ecological landscape, and the basic places to sustain human activities and developments in the arid area. Under the influence of the increasing human activities and the change of global climate, oasis change (Oasification and desertification) was not only the most direct reflect of environmental change in the arid area, but also was one of the most active research fields of land degradation and regional sustainable development. Recently, the interaction mechanism between oasis change and landscape pattern had been regarded as an important content of regional environmental change research in arid areas. In China, oases were mainly distributed in temperate and warm temperate desert areas, but only took up 4%-5% of the total area of the northwestern China. However, more than 90% of the population and 95% of social wealth were concentrated within these oases. Jinta oasis located in the Hexi Corridor in arid northwestern China, was not only a typical oasis with long agricultural history, but also was an agro-pastoral transitional zone and ecologically fragile area. Due to the rapid growth of population, economic pressure and excess exploitation using the resources, the ecological environment and sustainable development of Jinta oasis were greatly affected. Therefore, we took Jinta oasis as a case to study oasis spatio-temporal change from 1963 to 2009 and its influence on the landscape pattern. Based on Keyhole satellite photograph in the 1963, Landsat MSS images in the 1973, TM and ETM images from 1986 to 2009, the land cover were divided into two categories: oasis and desert. Oasis included farmland, grassland, woodland, water and residential area which based on classification criteria of Chinese National Technical Standard for Land-Use Survey; desert included salinized land, bare land, desert, Gobi and low coverage grassland which the vegetation cover degree ≤ 15%.The results were tested by the field investigation, the GPS sampling and interview with local people. After then, the process, trend and spatial pattern change in Jinta oasis and the characteristic of landscape pattern changes were analyzed by a set of mathematical statistical models and indice of landscape ecology. The results showed that: Jinta oasis was being in an unbalanced state, oasis scale and area expanded gradually with an increase of 167.37km2 during the period of 1963-2009. Simultaneously, the area of Jinta oasis achieved its maximum with 523.17km2 in 2009. The conversion between oasis and non-oasis was frequent and violent and showed a state of imbalance-balance-extreme imbalance condition, although the degree of conversion was different in different periods. And then, most change of the oasis happened as the reclamation of abandoned land and desert area, especially in the inner and outer marginal area of oasis, such as Yangjingziwan township, Xiba township, Sanhe-Dongba -Dazhuangzi township zone, Jinta-Zhongdong township zone. The area, size and spatial distribution of oasis influenced by human activity had resulted in fundamental changes of oasis landscape pattern. The fractal characteristics, dispersion degree and fragmentation of Jinta oasis were decreased, and the oasis landscape tended to be simple and uniform. All in all, in the latest 46 years, the spatio-temporal change of Jinta oasis drove the change of local landscape pattern to the decrease of the diversity, complex structure and landscape heterogeneity. 参考文献 相似文献 引证文献

Estimating Turbulent Heat Fluxes With a Weak-Constraint Data Assimilation Scheme: A Case Study (HiWATER-MUSOEXE)

A weak-constraint variational data assimilation (WC-VDA) scheme was developed to estimate turbulent heat fluxes by assimilating sequences of land surface temperature measurements. In contrast to the commonly used strong-constraint VDA system, the WC-VDA approach accounts for the effects of structural and model errors and generates better results. This is achieved by adding a model error term ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$\omega$</tex-math></inline-formula> ) to the surface energy balance equation. The WC-VDA model was tested at two sites with very distinct hydrological and vegetated conditions: the Daman site (a wet site located in an oasis area and covered by seeded corn) and the Huazhaizi site (a dry site located in a desert area and covered by sparse grass). The two sites represent typical desert–oasis landscapes in the middle reaches of the Heihe River Basin, northwestern China. The results proved that the WC-VDA method performed well over very dry and wet conditions, and the estimated sensible and latent heat fluxes agree well with eddy covariance measurements.

天山北麓绿洲-荒漠过渡带芨芨草地地表能量通量研究

Oasis-desert ecotone that lies between oasis and desert is bridgehead of the advance and retreat of Oasis( desert),which is ecological fragile zone taking on the trend of degradation. Its special characteristics of the surface energy exchange has a profound impact on the formation and development of the regional ecological environment. Therefore,better studying the law of surface energy transmission of oasis-desert ecotone can provide the scientific foundation of establishing the micro-climate model of the ecotone,achieving the optimal allocation of natural resources and promoting sustainable development of oasis. Based on the observed data of the experiment carried out in the oasis-desert ecotone of northern piedmont of Tianshan Mountains from July to September in 2010,the characteristics of the daily variations of the surfaceenergy balance,energy distribution and the relationship between latent heat and other surface energy were analysed. The results show that there are many differences in the daily variations of the surface energy under different weather conditions.Each energy component curve appears as‘single peak'type on clear day,whose circadian variation is significant. Affect by the variation of cloudiness,the curve of overcast day displays as ‘multiple peak 'type with peak and valley frequently alternating. Influenced by the precipitation change,the curve of rainy day manifests ‘partial peak 'type. Owing to the precipitation,the curve of average is basically consistent with the clear day. Unlike the most previous experimental results of the arid areas,the latent heat( LE) is the main energy transmission of the oasis-desert zone under any weather conditions,followed by sensible heat( H) and soil heat flux( G). The LE / Rn of sunny day reaches 72.4%.Due to the complement of the soil heat flux( G),LE / Rn of overcast day is up to 131%. As the transitional hydrothermal property and the dry-heat air transported by advection from desert,the average value of LE / Rn( 58. 8%) was much larger than Hexi Corridor desert,Dunhuang gobi for the same period in the arid zone,while smaller than the irrigated wheat area of oasis. That the average LE / Rn is between desert and oasis well reflects the transitional character of energy distribution. The daily changing trends of energy distribution under any weather condition are basically in accordance: energy of daytime is latent heat mainly and night is different. The curve of G / Rn、H / Rn and LE / Rn in daytime is smooth,that fluctuate continually in night,however,the most violent in sunrise and sunset. The LE / Rn and G / Rn curve of sunrise fluctuations strongest,which display the peakvalley complementarity. The Bowen ratio( 8: 00—18: 00) of the clear,average and overcast day decreases in turn. They are less than 1,indicating that energy distribution are mainly the latent heat in the daytime. However,the rainy day shows greater volatility with the upward trend as a whole. The correlation coefficients between LE and other energy including Rn,H,G are different due to weather condition. They are all highly correlated in clear days,followed by cloudy days and rainy days,while in clear days they show similar to the average condition.

塔里木河流域相对资源承载力研究

PDF HTML阅读 XML下载 导出引用 引用提醒 塔里木河流域相对资源承载力 DOI: 10.5846/stxb201309132265 作者: 作者单位: 广州地理研究所,中国科学院新疆生态与地理研究所,中国科学院新疆生态与地理研究所,中国科学院新疆生态与地理研究所,福建省城乡规划设计研究院,新疆维吾尔自治区发展改革委员会经济研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院部署项目子课题(KZZD-EW-06-03-03) Analysis of relative carrying capacity of resources in Tarim River Basin in Xinjiang Author: Affiliation: Guangzhou Institute of Geography,Xinjiang Institute of Ecology and Geography,CAS,Xinjiang Institute of Ecology and Geography,CAS,Xinjiang Institute of Ecology and Geography,CAS,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于改进的相对资源承载力模型,计算2000-2011年塔里木河流域的相对资源人口承载力和相对资源经济承载力,并探讨塔河流域42个县市相对资源承载力的演变规律及空间差异。研究表明:(1)改进的相对资源承载力模型具有一定的研究价值,对于拓宽相对资源承载力评价模型的应用具有实践意义。(2)以新疆为参照区,塔河流域2000-2011年处于人口严重超载、经济非常富余或富余阶段。(3)与全疆相比,土地资源是塔河流域的相对优势资源,水资源是制约塔河流域人口、经济发展的相对劣势资源。(4)以塔河流域为参照区,流域内42个县市的相对资源人口承载力和相对资源经济承载力的空间差异显著。(4)依据相对资源人口、经济承载力的超载、富余状态将塔河流域42县市归为A、B、C、D 4种资源承载力匹配区,并总结其时序演变特点和发展策略。 Abstract:A country's natural resources and economic resources form the basis of its regional sustainable development. Based on an improved model of the relative carrying capacity of resources, we calculate the relative carrying capacity of the population and that of the economy in the Tarim River Basin in Xinjiang from 2000 to 2011. We also discuss the temporal evolution and the difference in characteristics of 42 prefectures and cities in the Tarim River Basin. Most of the data were collected from the Xinjiang Statistical Yearbook (2000 to 2012), the Xinjiang City County Building Statistical Yearbook (2000 to 2011), and the Xinjiang Water Resources Bulletin (2000 to 2011). The Tarim River Basin is China's largest inland river basin, and is located in an arid area with a fragile ecological environment, poor local water resources, and a limited oasis area. In recent years, population growth, industrial development, and urbanization have accelerated the disparity between the supply and demand of land and water resources in the Tarim River Basin. The implications from this study are as follows: (1) The improved model of the relative carrying capacity of resources has a certain practical value in optimizing the relative carrying capacity of resources evaluation model. (2) In comparison with Xinjiang, the Tarim River Basin can be characterized as an overpopulated area with a surplus economy from 2000 to 2011. (3) Compared with Xinjiang, land resources are relatively plentiful in the Tarim River Basin, but water resources are relatively scarce, which restricts the population and economic development. Economic development relies on traditional agricultural production in the Tarim River Basin. Thus, in the Tarim River Basin, while land is a relatively advantageous resource, water can be considered as a relatively disadvantageous resource. In future, a more concerted effort needs to be made to improve the efficient use of water resources in the area, as well as to exploit the comparative advantage offered by the relatively abundant land resources. (4) The 42 prefectures and cities in the Tarim River Basin display significant spatial differences in terms of the relative carrying capacity of the population and the economy. Significant differences are also found between the sub-river basins in terms of these factors, which is a reflection of the complex physical geography of the area. (5) Based on the relative carrying capacity of the population and the economy, we classify the 42 prefectures and cities in the Tarim River Basin into four groups, and then summarize the evolution of each group's temporal characteristics and development strategies. After nearly 12 years of development and evolution, the relative carrying capacity of the population and the economy in the Tarim River Basin are still highly unbalanced in terms of the area's spatial pattern and distribution. The counties and cities in group B, which have a relatively insufficient economic scale, should become the key development areas in the Tarim River Basin. In contrast, the counties and cities in group C, which are relatively saturated in terms of their economic scale, but have a relatively small population, should become optimized development areas. 参考文献 相似文献 引证文献