Feedbacks of soil properties on vegetation during the Green Sahara period

During the early to middle Holocene, the Sahara received enhanced precipitation and was covered by steppe-like vegetation. However, most coupled land-atmosphere models underestimate the precipitation and vegetation cover, suggesting that critical atmospheric or land surface processes are lacking in models. Here, we examine in a land surface model five plausible soil-vegetation processes that may modify soil hydraulic properties. We show that these processes have strong positive impacts on vegetation and soil moisture, especially the increase of soil evaporative resistance. After considering all soil feedbacks on vegetation, the model requires precipitation of ~400 mm/yr to reproduce the pollen-inferred vegetation extension in the mid-Holocene Sahara. From the mid-Holocene to pre-industrial period, we infer that terrestrial carbon stocks decrease by ~58 PgC due to the removal of carbon in vegetation, soil and litter pools. We propose it is essential for future model studies to have a better representation of soil processes. These files contain output of our sensitivity simulations with ORCHIDEE-MICT land surface model.