Exploring plant distribution shifts in a non-stationary climate with an ecohydrological model

Hydro-climatic conditions control the spatial distribution of many plant species, and with a changing climate, shifts in distribution patterns are foreseen. Beyond affecting species distribution, climate change at high elevation is altering land cover with processes such as glacier retreats providing new terrains for plant colonization and succession. Predicting plant distribution shifts under climate change has led to the development of various models in different communities, including species distribution models (SDMs) and dynamic global vegetation models (DGVMs). SDMs are predominantly data-driven and DGVMs often simplify processes representation of energy and water budget or look at very large scales. At finer scales, ecohydrological models comprehensively reproduce key components of hydrological cycle and vegetation dynamics but typically cannot explicitly simulate plant distribution dynamics. To address these limitations, we incorporate a seed dispersal and establishment kernel into the T&C mechanistic ecohydrological model. The model features the migration and interaction of plant species while maintaining accurate representations of water and energy budgets alongside plant physiological properties. Two catchments that have experienced substantial vegetation shifts over the past decades are chosen as evaluation sites. This model exhibits good quantitative agreement with historical vegetation records and provides insights through sensitivity analysis into the environmental factors driving rapid shifts in plant distribution. We show that ecohydrological models, enhanced with seed dispersal and establishment mechanisms, could be potentially used to investigate plant distribution dynamics at the catchment scale and can deepen our understanding of how climate change influences plant encroachment and disappearance.