Spatiotemporal changes and driving forces of vegetation NPP in transition zone between the Loess Plateau and Qinghai Tibet Plateau: a case study of Datong County, Qinghai Province of northwestern China

Objective This paper explores the spatiotemporal variation characteristics and their driving factors of net primary productivity (NPP) of vegetation in Datong County, Qinghai Province of northwestern China, so as to provide data support for evaluating the sustainability and productivity of regional ecosystem.

Method Using MOD17A3, terrain, meteorological, and human activity data, vegetation NPP in Datong County was analyzed through methods such as trend analysis, partial correlation analysis, land use transfer matrix, and optimal geographic detector.

Result (1) From 2000 to 2019, the multi-year average NPP value in Datong County was 331.77 g/m² （calculated by C, the same applies below）, increasing at a rate of 2.29 g/(m²·year), with a distribution pattern characterized by higher values in the southeast and lower values in the northwest. The contribution rate of grassland vegetation to NPP was the highest. Significant increases were observed in 70.10% of the area, while only 0.51% significantly decreased. (2) The increase in vegetation NPP was driven by both climate change and human activities, with spatial heterogeneity from various driving factors. Precipitation, sunshine duration and temperature showed positive correlations with vegetation NPP in the southeastern, northwestern, and entire region of Datong County, respectively. Population density and GDP respectively had a promoting effect on vegetation NPP in high-altitude grasslands and low-altitude afforestable areas. (3) Temperature, precipitation and elevation were the dominant factors affecting spatial variations of vegetation NPP, and the interaction among driving factors were dual-factor enhancement and nonlinear enhancement. When the elevation, slope, annual precipitation, annual temperature, and population density were 2 840−3 150 m, 4.18°−10.80°, 441−677 mm, 1.18−3.56 ℃, and 126−413 person/km², respectively, the growth of vegetation NPP can be promoted effectively.

Conclusion In most areas of Datong County, vegetation NPP has shown a significant increasing trend, with both climate change and human activities contributing favorably to vegetation growth. The results are helpful to further understand the potential driving mechanism of NPP changes in the Loess Plateau and Qinghai Tibet Plateau transition zone, which holds significant implications for regional ecological conservation and sustainable development.