Assessing the impact of land conversion and management measures on the net primary productivity in the Bailong River Basin, in China

Abstract

To cope with and reduce environmental degradation, the Chinese government initiated a series of new, national-scale policies and ecological projects in the late 1990s and early 2000s. However, under different political systems, the impact of such restoration measures on vegetation productivity in the Bailong River Basin (BRB) in China is unclear. Here, based on the analysis of the LUCC from 2000 to 2019, we quantitatively distinguished the contribution of climate change and human activities (including land conversion and management measures) to the change of vegetation net primary productivity (NPP). The results showed that from 2000 to 2019, the area of cultivated land decreased by 405.1 km2, which was mainly attributed to the conversion to forestland and grassland. The average NPP of BRB increased at a rate of 0.0063 kg C m−2 a-1. We found that there were two distinct growth periods, and the growth rate of NPP after 2012 (Period 2) was higher than that before 2012 (Period 1). Compared with the total amount of NPP in Period 1, that in Period 2 increased by 1,323.001 Gg C a-1, of which human activities and climate change accounted for 70.16% and 29.84%, respectively. The land conversion increased the NPP by 219.115 Gg C·a-1, whereas management measures increased the NPP by 709.09 Gg C·a-1 in the otherwise unmodified land. In Period 1, climate change had a major positive impact on the increase in NPP. In Period 2, after the implementation of the ecological projects, human activities played a major positive role in the increase in NPP. Therefore, actively implemented ecologically reasonable management measures in the study area is the main driving force for increasing NPP.