Spatial and temporal characteristics of vegetation carbon use efficiency and its response to drought in the Manas River Basin, Xinjiang, China

Carbon Utilisation Efficiency (CUE) is the ratio of carbon used by organisms for growth and development to the total carbon they have absorbed, and plays a crucial role in the carbon cycle. The terrestrial ecosystems in the Manas River Basin in Xinjiang are rich in variety, and exploring the changes in CUE of vegetation in different ecosystems in the region and their impacts can help to understand the trend of carbon change in the region under the background of climate change, which is important for assessing the regional ecosystems‘ carbon sink capacity and promoting management measures to increase the ecosystems’ solid potential. This study employed MODIS data products, we calculated the CUE of the Manas River Basin in Xinjiang from 2001 to 2020 year by year, and analysed the evolutionary trends of the CUE of coniferous forests, broadleaf forests, grasslands, and croplands, as well as their response mechanisms to drought by using methods such as statistical analyses, stability analyses, and correlation analyses. The results showed that: (1) the mean value of CUE in the Manas River Basin in Xinjiang was 0.501 over 20 years, with the highest CUE in coniferous forests and the lowest in crops; the mean value of CUE was the highest in spring and autumn, while the lowest value, 0.01, was observed in winte. (2) CUE fluctuations in the 57.99% of the total area of the watershed were low, and the low-fluctuation areas were mainly distributed in the grassland and woodland areas of the study area; the middle and lower reaches of the watershed had the lower fluctuations in CUE. woodland areas; plain grasslands in the middle and lower reaches of the watershed and desert grasslands in the northern part of the watershed showed opposite persistence trends in the future. (3) For the Manas River Basin, most CUE response lags to drought were detected at the 3-month scale. The forest land was more resistant to drought and the CUE response to drought was more lagged. (4) The overall resilience of vegetation CUE to drought disturbance in the study area was good. The spatial and temporal characteristics of vegetation CUE are the result of a combination of factors, whose interactions and feedback mechanisms jointly determine the carbon use efficiency of vegetation. The study’s findings are crucial for understanding the dynamic characteristics of vegetation CUE in the study area, and its response information to drought.