Distribution of Podocarpus latifolius/milanjianus from the Last Glacial Maximum to 2100 in Africa with the dynamic vegetation model CARAIB.

Podocarpus latifolius/milanjianus (same species according to genetics) is an endemic African species with populations in the western, eastern and southern parts of the continent. The current global warming threatens the conservation of the relict patches of this mountain evergreen species. During the Last Glacial Maximum (LGM), the species was certainly more largely distributed and present at lower elevations than today according to pollen data. At the beginning of the Holocene, Podocarpus moved upwards due to warmer conditions. The size of the populations might have collapsed abruptly at the end of the ”African Humid Period” at ca. 3,000 BP. Besides this general evolution, the palaeo-distribution of Podocarpus remains relatively unknown. The origin and connections between the eastern, southern and western Podocarpus forests are still not understood.

In the framework of two related projects, AFRIFORD and VULPES, we use the CARAIB dynamic vegetation model, in parallel to genetic and palynologic analyses, to simulate the past and future dynamics of Podocarpus and to understand its current distribution. Projections of the HadCM3 climate model are used to reproduce climatic conditions in Africa from LGM (21,000 BP) to present time with a temporal resolution of 1 kyr. For the future (until 2100), several IPCC CMIP5 climate scenarios have been selected according to the quality of their reconstructed climate (temperature and precipitation) over sub-Saharan Africa for historical period. After interpolation to a 0.5° regular grid, we kept only past/future anomalies that we added to the GSWP3 (20 CR) climate data chosen as the reference for the historical period. Sub-continental simulations are performed with CARAIB forced by these climatic projections to simulate the net primary productivity of Podocarpus over time and space. In addition, CARAIB simulations are performed at higher resolution over a restricted region in southwestern Cameroon to identify potential microrefugia.