Effects of land use patterns on the interannual variations of carbon sinks of terrestrial ecosystems in China

Land use changes are thought to deeply impact the changes of terrestrial carbon sink, however, how the changes of land use pattern affect the carbon sink remains unclear. To investigate the response of Net Ecosystem Pro-ductivity (NEP) to the pattern of land use dynamics in China, a landscape pattern approach (with the 30 km moving window) was used to analyze the pattern dynamics with continuous Land Use and Land Cover Change (LUCC) data from 1981 to 2019 and the nonlinear trends of the NEP and the patterns of land use were explored from 1981 to 2019 using Ensemble empirical modal decomposition (EEMD) methods, and their interannual relationship was further explored using Pearson correlation. The results are as follows: (1) For NEP, nearly half of the regions did not experience significant changes. <6 % of the regions were monotonically decreasing and increasing to decreasing. The monotonical increasing only accounted for 15.49 % of the study area, while the trend shift from decreasing to increasing accounted for 23.96 %, most predominantly located in the southern part of the Southern Region (SR); (2) For land use patterns, the vast majority of areas (>90 %) have experienced significant changes in land use patterns, the fragmentation and shape complexity, diversity and evenness of land use types has increased, while the connection decreased, meanwhile, most of these changes are not monotonical, but experiencing trend shifts; (3) In most of the total area (>80 %), land use patterns showed insignificant relationship with NEP, especially in Qinghai-Tibetan Plateau. However, in Greater Khingan Range, Loess Plateau and southern Hilly area, it showed significant relationship with NEP. Our studies highlight the importance of nonlinear analysis for fully understanding the spatial-temporal changes of NEP and land use patterns, and deepened the understanding the impacts of land use changes on NEP.

Automated summary

This study used landscape pattern and data analysis methods to explore the impact of land use dynamics on Net Ecosystem Productivity (NEP) in China. The results showed that most regions did not experience significant changes in NEP, while land use patterns exhibited increased fragmentation and shape complexity, decreased connectivity, and trend shifts. The relationship between land use patterns and NEP was insignificant in most areas, but significant in some regions. These findings emphasize the importance of nonlinear analysis in understanding the spatial-temporal changes of NEP and land use patterns, and deepen our understanding of the impacts of land use changes on NEP.