Abstract:

In this study, the oasis-desert transition zone at the northern margin of Tarim Basin was divided into three types: oasis with stony bare mountains, sandy desert, and gravelly desert, used Landsat remote sensing image data of the oasis at the northern margin of Tarim Basin, supplemented by Google Earth Pro 4800-pixel high-resolution remote sensing images to establish interpretation markers. At four different scales (30, 60, 90, and 120 m), the NDVI of the oasis edge showed two linear trends, and the distance between the intersect of the two trend lines and the oasis boundary was determined as the width of the ecotone. At the same time, buffer zone analysis and focal point analysis methods for different scales were used to analyze the width and scale dependence characteristics of the transition zone in the northern edge of Tarim Basin from 1994 to 2020. The results showed that the linear trend of NDVI changes in the northern margin of the Tarim Basin were all highly significant (P<0.01), and the width of the oasis-stony bare mountain transition zone was stable at 540 m from 1994 to 2020. Meanwhile, the width of the transition zone between the oasis and gravelly desert had decreased year by year, from 540 m in 1994 to 420 m in 2009 and 360 m in 2020. Moreover, the width of the transition zone between the oasis and sandy desert had also significantly decreased, from 600 m in 1994 to 420 m in 2009 and 300 m in 2020. This was mainly due to the continuous increase in the area of cultivated land at the edge of the oasis gravel desert and sandy desert in the northern margin of Tarim Basin in the last 30 years, At the same time, the temperature and precipitation decreased, and the changes in both anthropogenic activities and natural climate led to the gradual shrinkage of the width of the transition zone between oasis-gravelly and sandy desert. However, the area of bare rock surface had not changed, and the width of the oasis stone bare mountain transition zone had remained stable. The findings showed that the process of oasis transformation in the northern margin of Tarim Basin had significantly accelerated, and the width of the transition zone between the oasis gravel desert and the sandy desert had decreased significantly. There is thus a need for further efforts to protect and improve the environment in the oasis-desert transition zone in this region.

Key words: width of oasis-desert ecotone, buffer analysis, focal analysis, northern margin of the Tarim Basin