Analysis of the Characteristics and Mechanism of Spatial and Temporal Changes in Net Primary Productivity (NPP) in Northwest Liaoning Province

Abstract

This study used Theil–Sen median trend analysis and Mann–Kendall test, which are more suitable for long-term series research, to analyze high-precision NPP data and investigate the spatiotemporal characteristics of NPP (net primary productivity) in northwest Liaoning from 2001 to 2021. We further analyzed the impact of the natural environment and land use types on NPP in the region using correlation and a one-way linear regression analysis. The results show that (1) the interannual NPP values exhibited a generally increasing yet fluctuating trend, with the gradient of NPP decrease moving from northwest to southeast. (2) NPP in northwest Liaoning was predominantly influenced by climatic variations, with significant impacts from the combined precipitation–temperature effects seen in 74% of the region, 65% influenced by precipitation alone, and 26% by non-climatic factors. (3) The interaction of soil and vegetation also impacted NPP, which displayed variable rising trends across different soil types in northwest Liaoning. (4) Alterations in land use led to a hierarchical arrangement of the multi-year average NPP values, listed from highest to lowest as forest land, grassland, cultivated land, built-up areas, unused land, and watersheds.