The Variability of Net Primary Productivity and Its Response to Climatic Changes Based on the Methods of Spatiotemporal Decomposition in the Yellow River Basin, China

The fragile ecosystem in the Yellow River Basin (YRB) is sensitive to climatic changes, and previous studies have mainly focused on exploring the spatiotemporal relationship between vegetation growth and climatic change based on their spatially or temporally averaged values. However, few studies unraveled the effect of climatic changes on vegetation growth from both spatial and temporal variations separately. In the study, empirical orthogonal function (EOF), singular value decomposition (SVD), and trend analysis were used to detect the spatiotemporal variation of net primary productivity (NPP) over 2000-2019 and to analyze its response to climatic factors from spatial and temporal aspects, respectively, in the YRB. The results showed that the distribution of NPP decreased from southeast to northwest. The areas of NPP with significantly improved and degraded accounted for 80.41% and 1.3%, respectively. The NPP had greatly increased after 2012, particularly in the central region, but decreased in the eastern region. Precipitation was the dominant factor influencing NPP growth, especially in the arid and semi-arid regions. Additionally, the characterization of variability in farmland and forest land by EOF was better than SVD. This study provides insights into the relationship between vegetation growth and climatic changes at a watershed scale.