Projected spatiotemporal shifts in forest community suitability in the northeastern Qinghai-Tibet Plateau under climate change.

The northeastern Qinghai-Tibet Plateau (QTP) constitutes a critical ecological security barrier and an important terrestrial carbon sink in China. Forest community in this region plays an indispensable role in water conservation, soil retention, and carbon sequestration. However, it remains unclear how ongoing climate change is expected to alter the distribution patterns of forest community. Here, using 2,892 forest community occurrence records, we developed random forest (RF) models to project changes in climatically suitable habitats for different forest community types under two climate scenarios: a sustainability pathway (SSP1-2.6) and a regional rivalry pathway (SSP3-7.0). Our results indicate that the total area of climatically suitable forest habitats is projected to expand substantially under both scenarios, with the overall suitable area expanding by approximately twofold compared with the current period. Responses, however, vary among community types, with evergreen coniferous forest (ECF) showing the most pronounced increase in suitable habitats, whereas the expansion of deciduous broadleaf forest (DBF) is relatively limited. Spatially, forest suitable habitats are projected to expand primarily in the eastern Qilian Mountains and northern Gannan Plateau, which represent potential hotspots for forest expansion. In contrast, areas currently suitable for ECF on the northern slope of the Qilian Mountains and for DBF in the southern mountainous regions of the Gannan Plateau are projected to become unsuitable under climate conditions, suggesting a redistribution of forest community along regional climatic gradients. These findings highlight contrasting climatic sensitivities among forest formations and underscore the urgency of incorporating climatic suitability into forest conservation and management strategies.