Abstract:

To investigate the impact of hydrothermal conditions on vegetation net primary productivity (NPP) in the “Three Water Lines” (Heihe-Tengchong Line, Yangguan Line, and Qitai-Cele Line) region of Northwest China, we employed an enhanced version of the CASA (Carnegie-Ames-Stanford Approach) model to estimate NPP in the study area from 2001 to 2020 based on remote sensing and meteorological datasets. Regression and correlation analyses were also conducted to scrutinize the temporal and spatial NPP variations and their responses to hydrothermal factors. Our findings revealed a fluctuating upward trend in vegetation NPP from 2001 to 2020, with an average annual increase of 1.54 gC/(m²·a). Notably, region III, located west of the Qitai-Cele line, exhibited the most rapid growth rate at 2.39 gC/(m²·a). Spatially, the majority of the study area demonstrated an increasing NPP trend, with 47.27% showing significant increases, predominantly in the central and southern parts of region I (east of the Yangguan Line) and the southwestern portion of region III. Conversely, only 0.79% of the area experienced a significant decrease in NPP. Regarding the influence of hydrothermal conditions, precipitation emerged as the dominant factor, contributing to 31.53% of NPP variation, surpassing the contribution of air temperature at 9.58%. This suggests that both temperature and precipitation positively influence NPP changes in the region, with precipitation playing a more pivotal role.

Key words: net primary productivity, climatic factor, CASA model, Three Water Lines, Northwest China