Spatiotemporal Dynamics of Pinus fenzeliana Suitable Habitat from the Last Glacial Maximum to 2070: An Ensemble Modeling Approach

Climate change poses an increasing threat to tropical montane conifer species, many of which persist in narrow elevational ranges with limited adaptive capacity. Pinus fenzeliana is an endangered pine endemic to montane forests of southern China and northern Vietnam, yet its historical and future climatic niche dynamics remain poorly understood. In this study, we employed an ensemble species distribution modeling (SDM) approach using the biomod2 platform to reconstruct the suitable habitat of P. fenzeliana from the Last Glacial Maximum (~21,000 years BP) to 2070 under two CMIP6 climate scenarios (SSP126 and SSP370). Seven modeling algorithms were calibrated with occurrence records and eight selected bioclimatic variables. The ensemble model demonstrated high predictive performance across spatial block cross-validation (mean AUC-ROC = 0.876, TSS = 0.730, BCI = 0.641). Variable importance analysis identified the minimum temperature of the coldest month (BIO6, 37.9%), precipitation of the driest month (BIO14, 17.0%), precipitation seasonality (BIO15, 13.6%), and mean temperature of the wettest quarter (BIO8, 11.1%) as primary determinants. Climatically suitable habitat expanded by 8.3% from 1,100,947 km2 at the LGM to 1,192,711 km2 at present, accompanied by an upward median elevation shift from 933 m to 1304 m and a ~200 km northward shift in the habitat centroid. Under 2070 climate scenarios, suitable habitat is projected to contract to 1,066,938 km2 (−10.5%, SSP126) and 882,705 km2 (−26.0%, SSP370), with median suitable elevations rising to 1490 m and 1528 m, respectively. Geographic centroids are projected to shift a further ~82 km (SSP126) and ~121 km (SSP370) north-northeastward. Furthermore, only 3.57% of current suitable habitat falls within protected areas, declining to 2.43% (SSP126) and 2.82% (SSP370) under future climates. These findings indicate that while the climatically suitable habitat of P. fenzeliana expanded from the LGM to the present, future climate warming is projected to cause substantial habitat contraction, elevational compression, and protected-area decoupling. Our results underscore the urgency of integrating climate refugia protection, transboundary ecological corridors, and assisted gene flow into conservation planning for threatened Asian montane conifers.