Climate response patterns and prediction of potential suitable distributions of four typical spruce species in China

Spruce is an important ecological and timber tree widely distributed in high-latitude and high-altitude regions. Early human deforestation and climate change have severely disrupted the natural distribution of spruce. Understanding the historical changes in the potential suitable habitats of spruce and its climatic response patterns is of great significance for its resource conservation and utilization. This study analyzed the response patterns of four geographically distributed spruce species in China (Picea asperata, P. crassifolia, P. koraiensis, and P. schrenkiana) to 19 climatic factors, 8 soil factors, and 3 topographic factors. Using the Maximum entropy (MaxEnt) model, the potential suitable habitat changes for these four spruce species were simulated for historical periods (Last Glacial Maximum, LGM, and Mid-Holocene, MH), the present, and future scenarios under different emission pathways (SSP1-2.6 and SSP5-8.5). The results show that the Area Under the Curve (AUC) values for the distribution models of the four spruce species are all exceed 0.92, indicating high predictive accuracy. The main factors influencing the distribution of P. asperata are temperature-related factors (Mean temperature of the wettest quarter, Mean temperature of the coldest quarter, Temperature seasonality). Both temperature (Isothermality) and precipitation (Precipitation of the driest month) significantly contribute to the distribution of P. crassifolia. The distribution of P. koraiensis responds to soil factors (Sand and Silty) and precipitation factors (Precipitation seasonality and Precipitation of the wettest month). From historical periods to the present, the suitable habitat areas for all four spruce species have significantly decreased. In the future, the suitable habitat ranges for P. koraiensis and P. schrenkiana may increase, but the distribution areas of P. asperata and P. crassifolia may further decline. Enhancing the establishment of plantations within the suitable habitats of spruce (especially P. asperata and P. crassifolia) and strengthening the protection of populations in marginal areas are currently key priorities for consideration.