[Quantitative Separation of Spatiotemporal Patterns and Driving Factors of Carbon Sequestration Benefits in the Beijing-Tianjin-Hebei Region]

Abstract

Net ecosystem productivity （NEP） is an important indicator for evaluating carbon sources and sinks in regional ecosystems. Clarifying its spatiotemporal differentiation pattern and driving mechanisms is crucial for precise protection and restoration of the Beijing-Tianjin-Hebei ecosystem. We estimated the net ecosystem productivity （NEP） based on MODIS remote sensing data and explored the spatial and temporal patterns of carbon sequestration benefits and succession patterns in the Beijing-Tianjin-Hebei Region from 2002 to 2020 by using Sen's trend + MK test, Hurst index, and center of gravity shift and quantitatively separated the relative contributions of carbon sequestration benefits driven by human activities and climate change by using bias correlation, complex correlation, and residual analysis. The relative contributions of anthropogenic activities and climate change in driving the spatial and temporal changes in carbon sequestration were quantitatively separated using partial correlation and residual analysis. The results showed that： ① NEP in the Beijing-Tianjin-Hebei Region showed an increasing trend year by year over the past 20 years, with a growth rate （in terms of C） of 3.066 4 g·（m²·a）^-1, and the spatial manifestation was high in the northwest and low in the southeast； the areas with strong carbon sink capacity were mainly concentrated in the periphery of Zhangjiakou City and Chengde City, and those with a strong carbon source effect were distributed in the regions of Tianjin and Handan. More than 80% of the regional carbon sink capacity was on the rise, with 47.45% and 8.29% of the regions showing very significant and significant increases, respectively, especially in Zhangjiakou and Chengde； however, the future growth trend was gradually slowing down. The center of gravity of carbon sources was gradually shifting to the southeastern plains, while the center of gravity of carbon sinks was shifting from the northeast to the southwest. ② More than 50% of the regions showed positive correlations between NEP and mean annual temperature and accumulated annual precipitation； however, the significance was not strong, and the results of the composite correlation further demonstrated that there were conditions other than meteorological factors that dominated the changes in NEP. ③ The residual results showed that the proportion of degraded and improved areas in the study area was 12.41% and 87.59%, respectively, with areas of enhanced human-led carbon sequestration accounting for 94.88% of the total improved areas, while the climate-led carbon sequestration benefit reduction area accounted for 62.84% of the degraded area, indicating that anthropogenic activities in the Beijing-Tianjin-Hebei Region mainly contributed positively to ecosystems in terms of carbon sequestration benefit. The results of the study are instructive for accurately identifying the future focus of ecological protection and restoration in the Beijing-Tianjin-Hebei Region.

Keywords: Beijing-Tianjing-Hebei Region; anthropogenic activities; carbon sequestration benefits; net ecosystem productivity （NEP）; spatial and temporal patterns.