中国西南农村人口减少对植物多样性的影响及阈值效应研究OA

Although the global population continues to grow,the coming decades will witness the most rapid expansion of urban population in human history,primarily,driven by large-scale rural-to-urban migration.This migration alleviates human pressure significantly in rural areas,promotes the transformation of land use patterns and ecosystem restoration,and profoundly reshapes regional land spatial configurations.These changes directly or indirectly affect local ecological environments,thereby presenting both new opportunities and challenges for biodiversity.The southwestern region of China serves as a critical ecological security barrier for the country.It is not only a key area for global vegetation greening and plant diversity conservation,but also a typical region experiencing marked rural-urban migration and a pronounced decline in rural population.The ongoing and accelerating outflow of rural population in this region is profoundly reshaping local human-land relationships.Moreover,its distinctive karst landforms and ecological fragility make it highly sensitive to human disturbances.While large-scale rural population decline is reshaping the ecological environment,it also creates opportunities for ecosystem restoration.However,the response mechanisms of plant diversity to rural population decline and its threshold effects remain unclear,which hinders a deeper understanding of the coupling mechanisms in human-earth systems and constrains the scientific rigor and effectiveness of regional ecological conservation strategies. This study focuses on southwestern China as the research area.Based on vascular plant species richness data,the spatial pattern of plant diversity from 2000 to 2020 was reconstructed using a Random Forest model.The K-means algorithm was employed to identify urban-rural boundaries,revealing the spatiotemporal evolution characteristics of the rural population and examining the impact of rural population decline on plant diversity and its threshold effects.Using the human footprint index to characterize human pressure,the relationship between the release of human pressure induced by rural population decrease and the increase in biodiversity was analyzed.Through relative contribution rate decomposition,the driving contributions of climate change and human pressure were quantified.The study addresses the following key questions:(1)Spatiotemporal patterns of population decline in southwestern rural China;(2)Impacts of population decline on the spatial distribution of plant diversity and underlying mechanisms;(3)Threshold responses of plant diversity to changes in population density;(4)Relative contributions of climate change and human pressure to plant diversity changes. The results indicate that between 2000 and 2020,southwestern China experienced a rural population decrease of approximately 137 million,a 5.23％reduction in human pressure,and a significant 44.32％increase in plant diversity.Over 60％of the areas with rural population loss showed significant increases in plant diversity,with an average increase of approximately 0.73 species per 100 km2,across an area of 266,600 km2,Further analysis revealed a nonlinear relationship between rural population density and plant diversity:when population density fell below 336.68 persons·km-2,population decline exerted a suppressive effect on plant diversity;within the range of 336.68 to 956.73 persons·km-2,this suppressive effect gradually weakened;and when density exceeded 956.73 persons·km-2,population decline transitioned to a positive facilitative effect.Decomposition of driving factors showed that changes in rural human pressure contributed 38.64％to plant diversity changes,while climatic factors accounted for 61.36％,indicating that climate change remains the dominant factor influencing regional plant diversity. This study quantifies and reveals for the first time the nonlinear relationship and key thresholds between rural population decline and plant diversity in southwest China.It systematically elucidates the response mechanisms of plant diversity to population decline and human pressure,and clarifies the relative contributions of human activities and climate change.By analyzing the response patterns of plant diversity to rural population outmigration and identifying critical thresholds of population density effects,this research provides a scientific basis for understanding the mechanisms by which rural-urban migration influences biodiversity.The findings offer important insights for biodiversity conservation and regional sustainable development in southwest China.