Spatiotemporal changes of land use/cover from 1995 to 2015 in an oasis in the middle reaches of the Keriya River, southern Tarim Basin, Northwest China

Abstract

Land use and land cover (LULC) changes in oases have been a topic of great interest due to the impacts of oases on ecosystem services in arid regions. The oasis that is along the Keriya River in southern Tarim Basin, northwest China, is in an ecologically fragile region and is thus very sensitive to human interference. In this study, the spatial and temporal changes in LULC in the middle reaches of the river were quantified and assessed by using GIS technology based on remote sensing images from 1995, 2005 and 2015. The results indicated that cropland expansion and grassland degradation were the dominant LULC changes, especially in the last decade. Throughout the study period, cropland areas increased by 6.51%, while grassland areas decreased by 30.98%. A buffer analysis along the main river channel was conducted to analyze the spatial LULC characteristics. The results showed that water areas, croplands and forests were predominantly distributed along the river (in the 0–10 km buffer). The majority of mid-density grasslands and low-density grasslands were distributed in the 10–20 km buffer, and high-density grasslands were mainly distributed in the 20–30 km buffer. The conversion rates in different buffers indicated that cropland expansion primarily occurred along the river, and grassland degradation was noted in the 10–30 km buffer. Landscape pattern changes were also analyzed to account for the structural LULC characteristics. The results that were deduced from the landscape pattern change analysis showed that the patch structures of forestland and cropland increased, and increasing fragmentation tendencies were found in the other LULC types. Moreover, a model was introduced to quantify the directions of LULC changes, and the results showed that the direction of LULC change in the oasis was declining, which represents an undesirable change in LULC. Socio-economic changes were also analyzed to explain the LULC changes. The results of this study contribute to the future management of the LULC in the oasis and the protection of the Keriya River ecosystem.