Quantitative estimation of the factors impacting spatiotemporal variation in NPP in the Dongting Lake wetlands using Landsat time series data for the last two decades

Abstract

Wetlands are important ecosystems and constitute one of the major carbon reservoirs on Earth. Therefore, accurate estimation of wetland carbon stocks, quantitative analysis of spatial and temporal changes in wetland carbon stocks, and maintenance and enhancement of wetland carbon sink functions play a pivotal role in achieving China’s “carbon neutral” strategy. Vegetation net primary productivity (NPP) is one of the core components of wetland ecosystem carbon budgets. In this study, an improved CASA model and the spatiotemporal fusion algorithm were employed to obtain NPP data with good accuracy and high spatiotemporal resolution for the Dongting Lake wetland area for the last two decades. Quantitative methods based on partial derivatives were used to assess the contribution of climate and anthropogenic factors to NPP changes. The results demonstrate that the NPP of wetland vegetation in Dongting Lake showed a significant increasing trend from 2000 to 2019 (0.86 g C/m2-yr, P < 0.05). Temperature, precipitation and solar radiation contributed positively to the NPP changes in wetland vegetation, with solar radiation making the greatest contribution (10.31 g C/m2·year), followed by precipitation (1.61 g C/m2·year) and then temperature (0.03 g C/m2·year). The contributions of climate change and human activities to changes in wetland vegetation NPP were 1.08 and 0.58 g C/m2·year, respectively. Human activities dominate in terms of vegetation degradation, while climate dominates in terms of vegetation restoration.