Abstract:

Based on the Landsat MSS/TM/OLI remote sensing images in 1976, 1989, 1998, 2006 and 2016, the information of oasis distribution in the Manas River Basin in recent 40 years was extracted, and the methods of mathematical statistics model and landscape index were used to analyze the spatiotemporal evolution of the oasis and the change of landscape patterns in the study area. The results showed that, in recent 40 years, the oasis in the middle and lower reaches of the Manas River Basin was in a trend of reduction-expansion-sharp expansion, except the oasis was retreated from 1976 to 1989, the oasis was expanded after 1989, especially during the period from 2006 to 2016, area of the oasis was expanded by 3 266 km², and the net change rate was as high as 4.43%. The change trend of the oasis was imbalanced and even extremely imbalanced. From 1989 to 2006, the contribution of grassland to the oasis reduction was the highest. After 2006, the reduction of waters was the main contributor to the oasis retreat. After 1989, the contribution of cultivated land to the oasis expansion was the most significant. The main part of the oasis was holistically shifted northwestward, and it was shifted northeastward, southwestward, northwestward and southwestward during different periods. The geometric shapes of the landscapes in the oasis were trended to simplification, and the fragmentation of the landscapes in the oasis became more serious, which was related to the increasing fragmentation of the grassland landscape. The oasis was trended to centralization, which was closely related to the continuous centralization of cultivated land.

Key words: oasis')">

oasis, spatiotemporal evolution, landscape pattern, area change, contribution rate, Manas River Basin