Spatiotemporal variation pattern and spatial coupling relationship between NDVI and LST in Mu Us Sandy Land

Normalized difference vegetation index (NDVI) and land surface temperature (LST) are important indicators of ecological changes, and their spatial and temporal variations and spatial coupling can provide a theoretical basis for the sustainable development of the ecological environment. Based on the MOD13A1 and MOD11A2 datasets, the spatial distribution characteristics of NDVI and LST from 2000 to 2020 were analyzed, and the trend change slope method and spatial coupling model were used to calculate the significant changes. Finally, the spatial coupling model was used to calculate the spatial coupling degree between NDVI and LST. The study shows that: (1) From 2000 to 2020, the annual NDVI value of the Mu Us Sandy Land was between 0.25 and 0.43, showing a stable upward trend overall, with an increase rate of 0.074/(10a). The proportion of improvement areas in the study area is 81.48%. (2) There are significant differences in the spatial distribution of surface temperature in Mu Us Sandy Land, showing an overall trend of decreasing from northwest to southeast and higher in the west than in the east. The LST of Mu Us Sandy Land is greatly affected by changes in land use types. The spatiotemporal variation trend of LST is different from the gradual warming trend of global climate change. The main reason is that human activities have changed land use types and increased local vegetation coverage. (3) There is a significant negative correlation between LST and NDVI in Mu Us Sandy Land, with an R 2 of 0.5073 and passing the significance test at the 0.01 level. This indicates that ecological engineering policies can effectively reduce LST in the study area, thereby achieving the effect of improving the environment. The overall spatial coupling between LST and NDVI is at a very high level, with an average coupling degree of 0.895 in the study area. The two mainly exhibit a state of mutual antagonism in space, reflecting the importance of green vegetation in regulating regional climate and LST. The vegetation index and spatiotemporal variation of LST in Mu Us Sandy Land are the result of the joint influence of human activities and climate change, and human activities dominated from 2000 to 2020.