Climate-driven habitat shifts of <i>Abies fargesii var. faxoniana</i> using the MaxEnt model

ABSTRACT Abies fargesii var. faxoniana, an endemic evergreen conifer of ecological and economic importance in China's montane regions, faces escalating threats from anthropogenic climate change. This study integrates paleoecological reconstruction and future climate scenarios to (1) decipher the species’ climate-distribution relationships, (2) identify critical bioclimatic thresholds, and (3) predict range shifts under warming scenarios. Using 60 georeferenced occurrence records and 19 bioclimatic variables, we developed a Maximum Entropy (MaxEnt) model with exceptional predictive accuracy (AUC = 0.997). The species’ potential distribution was reconstructed for four key periods: last glacial maximum (LGM, 22 kyr BP), mid-holocene (6 kyr BP), current era, and future scenarios (RCP 2.6 and 8.5 for 2050s/2070s) through ArcGIS-based spatial analysis. Key findings revealed that contrary to expected post-glacial migration patterns, the Sichuan Basin served as a Pleistocene microrefugium, with stable, suitable habitats (≥0.6 probability) maintaining 83.7% continuity since the LGM. Current optimal habitats concentrate in Sichuan (48.2%), Gansu (31.5%), and Shaanxi (17.3%), exhibiting &amp;lt;5% fluctuation since Mid-Holocene. Projected range reductions of 12.4% (RCP2.6) and 18.7% (RCP8.5) by the 2070s, primarily through elevational compression rather than latitudinal shifts. Thermal thresholds (Bio1, Bio7) explained 64.3% of distribution variance, interacting with precipitation extremes (Bio18-19) to define ecological amplitude.