Evaluation of spatiotemporal variation and impact factors for vegetation net primary productivity in a typical open-pit mining ecosystem in northwestern China

Abstract

The vegetation net primary productivity (NPP) is a key indicator for evaluating vegetation carbon sequestration. Exploring its spatiotemporal changes and impact factors is essential for coal mining and ecological restoration in open-pit mining areas. This study utilized the Carnegie-Ames-Stanford-Approach (CASA) model to calculate monthly vegetation NPP in the Xiwan mine area, a typical open-pit mine in northwestern China. The trend, stability, and persistence analysis were conducted, along with the development of a grading method to examine the vegetation NPP spatiotemporal variation across different land cover types. Statistical grading and correlation analysis were used to explore the relationships between the topographical factors, meteorological factors, human activities, and vegetation NPP. The following results were obtained: (1) The vegetation NPP in the study area exhibited a high stability and anti-persistent decrease in trend. NPP reached a peak of 143.49 g C/(m² year) in 2017, but declined to a low of 118.38 g C/(m² year) in 2021. (2) The vegetation NPP decreases with increasing elevation and slope, and a relatively strong correlation with temperature and precipitation was also observed. (3) The impact intensity of human activities on vegetation NPP exhibited a rising and fluctuating volatile trend. In 2021, the inhibition of vegetation NPP by human activities reached its peak at 166.42 g C/(m² year), with an impact effect share of 36.9%. This research provides a comprehensive framework for vegetation NPP analysis in open-pit mining, offering valuable insights for ecological conservation in mining ecosystems.