Past and future climatic indicators for distribution patterns and conservation planning of temperate coniferous forests in southwestern China

The distribution of forests can be hindcast or forecast when robust data and validation proofs are available. Distribution consequences for temperate coniferous forests during the Quaternary and future climatic fluctuations are little understood in China. Temperate coniferous forests are subdivided into two types where Pinus, Keteleeria, Tsuga and Cupressus species characterize the warm forests while Abies, Picea, Larix and Juniperus species characterize the cold forests. Both forest types were investigated using 12,675 unique records in the MaxEnt model to infer distribution patterns during six time periods: the present time, mid-Holocene, Last Glacial Maximum, Last Interglacial and the near- and far-future (2050, 2070). The results showed that the mean temperature of the driest quarter, followed by the temperature annual range and the precipitation of the warmest quarter were the most important variables controlling forests distribution. Suitable areas capable of supporting the presence of warm coniferous forests were highly contracted during the Quaternary; meanwhile, the cold coniferous forests expanded westwards from the last glacial maximum through the mid-Holocene to the present. The predicted future distributions showed a significant range-shift of warm forests northeastwards in response to climate change while cold coniferous forests are expected to migrate towards the Tibetan Plateau. Under increased global warming, the bioclimatic variables of the past and future periods were used as ecological indicators for the identification of areas showing climatic stability, and predicted to be refugia for coniferous forests and as good tools for conservation planning in Sichuan and the Hengduan-Tibetan migration corridor.