How the evaporation of dry dune grasslands evolves during the concerted succession of soil and vegetation

Sustainable water and vegetation management of coastal dunes requires fundamental knowledge of how interactions between soil, water, and vegetation evolve during succession. Therefore, we quantified the effect of succession on evaporation in dry dune grasslands of the Netherlands. On the basis of vegetation and soil records, we simulated the evaporation rate of vegetation plots that differed in successional stage, slope angle and slope orientation. Starting from bare sand, average yearly evaporation increased with 94 mm in a period of 52 to 76 years of soil and vegetation succession. The increase in evaporation was for the greater part caused by soil development (an increase of the water holding capacity) and the lesser part by an increase in vascular plant cover. In an early successional stage, ground layer evaporation could be both higher and lower compared to bare soil evaporation, depending on the moss species. At a later successional stage, moss species primarily decreased ground layer evaporation and facilitated vascular plants. Despite clear differences in slope angle and slope orientation, the simulated actual evaporation rate was not significantly correlated to the incoming solar radiation because the vascular plant cover and soil water holding capacity decreased with incoming solar radiation. These results show that biotic processes can eliminate the effects of micrometeorological differences on evaporation. On the basis of our findings, we hypothesize that vegetation shifts towards more moss- and lichen-dominated vegetation could mitigate the adverse effects of climate change (e.g., drier summers) on water resources