Spatio-Temporal Variation Characteristics of NPP in Weihe Watershed and Its Response to Environmental Factors Based on the CASA and CA–Markov Model

In this study, in order to simulate and predict NPP in the Weihe Watershed and examine its spatiotemporal coverage and dynamic variations, CASA and CA-Markov models are linked. To statistically assess the NPP response to environmental conditions, correlation analysis was used. Results revealed: (1) Seasonal fluctuations were noticeable on the time scale within a year, with the NPP in July being the highest and the NPP in January being the lowest. The forecast indicates that the vegetation of the watershed will continue to increase over the coming ten years based on the rising trend in the interannual change. (2) The NPP coverage is noticeably varied on a regional scale, with a generally high coverage in the south and east and a low coverage in the north and west. (3) The response of NPP to environmental conditions is notable but diverse. There was a weakly positive correlation between the response and climate parameters. With increasing slope and altitude, the NPP exhibits a bimodal tendency that continues to rise. The northern and western aspects’ NPP levels, meanwhile, were higher. (4) The high coupling degrees of the CASA and CA-Markov models are appropriate for the prediction of NPP in the Watershed.