This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950 s by rebuilding seven land cover maps derived from black-and-white aerial photographs（1958, 1968,...This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950 s by rebuilding seven land cover maps derived from black-and-white aerial photographs（1958, 1968, and 1978）, a color-infrared aerial photograph（1987）, Landsat Thematic Mapper（TM） imagery（1998）, Satellite Pour l＇Observation de la Terre（SPOT） imagery（2004）, and Landsat Operational Land Imager（OLI） imagery（2014）. The results showed that：（1） Since 1950, the oasis consecutively expanded more than four times from an alluvial fan to an alluvial plain, causing the shrinkage of desert landscapes that were dominated by a Haloxylon ammodendron Bunge community（HBC） and a Tamarix chinensis Lour community（TLC）. Furthermore, the primary（1958–1968） and final（2004– 2014） stages were the most important periods, during which agricultural land experienced the most rapid expansion during the period 1958–1968, and the built-up area showed the most rapid expansion after the 2000 s.（2） Two basic management modes, a ＂local mode＂ formed by the local governments and a ＂farm management mode＂ developed by Xinjiang Production and Construction Corps, together promoted oasis evolution under various land-use and landcover（LULC） stages.（3） The evolution of the modern oasis during the 1950s–2004 showed the general features of an arid oasis, while during the period of 2004–2014 it was characterized by a large-scale inter-basin water diversion or the import of new water sources.（4） The oasis expanded at the expense of desert vegetation, resulting in distinct variation in the structure of the desert plant community, which will make it more difficult to protect the desert ecosystem.展开更多
Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold islan...Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold island effect （OCIE） intensity, spatial-temporal variation of OCIE, factors influencing the OCIE and impacts of OCIE on air temperature using geographical statistics and GIS methods based on the MODIS land surface temperature, land use/cover change （LUCC） and observed air temperature data. Results showed that all the oases in the Tarim Basin exhibited cold island effects, with the OCIE intensity highest in summer （-9.08℃）, followed by autumn （-4.24℃） and spring （-3.85℃）. The total area of oasis cold island （OCI） and the comprehensive OCIE index showed the same seasonal change trend as the OCIE intensity. However, the changing trends in areas of OCI with strong, medium and weak OCIEs were inconsistent across different seasons. Farmland and water areas were found to be the key contributors that affected the OCIE, and the area and aggregation metrics of these two land use/cover types directly contributed to the OCIE. By contrast, natural vegetation, such as forest and grassland, almost had no contribution to the OCIE. Simulation of observed air temperature data showed that if farmland is replaced by forest or grassland in the oasis, the mean, maximum and minimum air temperatures will increase significantly. This heating effect will be higher in summer （reaching 1.14℃ to 2.08℃） and lower in spring and autumn. Moreover, the heating effect of farmland being replaced by forest will be higher than that of farmland being replaced by grassland. These results can provide a basis for understanding the cold island effect of oases in arid regions.展开更多
基金National Natural Science Foundation of China,No.U1303382 The National Basic Research Program of China,No.2014CB460603 The Project of State Key Laboratory of Desert and Oasis Ecology,No.Y471163
文摘This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950 s by rebuilding seven land cover maps derived from black-and-white aerial photographs（1958, 1968, and 1978）, a color-infrared aerial photograph（1987）, Landsat Thematic Mapper（TM） imagery（1998）, Satellite Pour l＇Observation de la Terre（SPOT） imagery（2004）, and Landsat Operational Land Imager（OLI） imagery（2014）. The results showed that：（1） Since 1950, the oasis consecutively expanded more than four times from an alluvial fan to an alluvial plain, causing the shrinkage of desert landscapes that were dominated by a Haloxylon ammodendron Bunge community（HBC） and a Tamarix chinensis Lour community（TLC）. Furthermore, the primary（1958–1968） and final（2004– 2014） stages were the most important periods, during which agricultural land experienced the most rapid expansion during the period 1958–1968, and the built-up area showed the most rapid expansion after the 2000 s.（2） Two basic management modes, a ＂local mode＂ formed by the local governments and a ＂farm management mode＂ developed by Xinjiang Production and Construction Corps, together promoted oasis evolution under various land-use and landcover（LULC） stages.（3） The evolution of the modern oasis during the 1950s–2004 showed the general features of an arid oasis, while during the period of 2004–2014 it was characterized by a large-scale inter-basin water diversion or the import of new water sources.（4） The oasis expanded at the expense of desert vegetation, resulting in distinct variation in the structure of the desert plant community, which will make it more difficult to protect the desert ecosystem.
基金funded by the National Natural Science Foundation of China(41571109)
文摘Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold island effect （OCIE） intensity, spatial-temporal variation of OCIE, factors influencing the OCIE and impacts of OCIE on air temperature using geographical statistics and GIS methods based on the MODIS land surface temperature, land use/cover change （LUCC） and observed air temperature data. Results showed that all the oases in the Tarim Basin exhibited cold island effects, with the OCIE intensity highest in summer （-9.08℃）, followed by autumn （-4.24℃） and spring （-3.85℃）. The total area of oasis cold island （OCI） and the comprehensive OCIE index showed the same seasonal change trend as the OCIE intensity. However, the changing trends in areas of OCI with strong, medium and weak OCIEs were inconsistent across different seasons. Farmland and water areas were found to be the key contributors that affected the OCIE, and the area and aggregation metrics of these two land use/cover types directly contributed to the OCIE. By contrast, natural vegetation, such as forest and grassland, almost had no contribution to the OCIE. Simulation of observed air temperature data showed that if farmland is replaced by forest or grassland in the oasis, the mean, maximum and minimum air temperatures will increase significantly. This heating effect will be higher in summer （reaching 1.14℃ to 2.08℃） and lower in spring and autumn. Moreover, the heating effect of farmland being replaced by forest will be higher than that of farmland being replaced by grassland. These results can provide a basis for understanding the cold island effect of oases in arid regions.
