Global Warming Drives Adaptive Distribution Dynamics and Habitat Fragmentation of Castanea seguinii in China

Castanea seguinii Dode is ecologically and economically significant in China, and its potential as a carbon sink and ability to adapt to varying climates have garnered considerable interest. In light of global warming, the geographical distribution of Castanea seguinii is experiencing notable changes. This study employs the Maximum Entropy (MaxEnt) model to forecast both present and future potential habitats conducive to the survival of Castanea seguinii across four emission scenarios (SSP126, SSP245, SSP370, and SSP585) and utilizes Fragstats 4.2 to analyze fragmentation in its most suitable regions. Findings reveal that current habitats that support adaptation are chiefly located in southern China, covering around 12.7% of the total land area of the country. Key factors affecting this distribution are precipitation levels during the driest month, average temperatures recorded in the driest quarter, precipitation rates in the wettest quarter, isothermality, and elevation, with climate-related variables exerting the greatest influence. As carbon emissions vary, a general trend of habitat contraction is observed for Castanea seguinii, especially in regions that are highly adaptive. The populations of Castanea seguinii are shifting northwestward into areas at higher latitudes and altitudes. This upward movement reflects pronounced nonlinear traits as the intensity of carbon emissions changes. An increase in carbon emissions leads to greater fragmentation in regions that are most adaptable, with the lowest and low fragmentation levels falling to a minimum by 2090 under the SSP585 scenario. The reduction in highly adaptive habitats will contribute to increasing fragmentation. These results offer vital scientific insights for the conservation and management of Castanea seguinii forest resources amid climate change and the pursuit of carbon neutrality.