Assessing long-term land-use legacies in subalpine grasslands using a plant-trait based generic modelling framework

Background: In European mountains, where semi-natural grasslands have high cultural and nature conservation value, land-use legacies from past ploughing are associated with distinct floristic compositions and ecosystem properties. It remains unknown if these differences are stable or if post-arable grasslands are only transient states that eventually follow a predictable successional pathway. Aims: We use a generic vegetation dynamics model based on plant traits to test these alternative hypotheses in subalpine grasslands of the central French Alps. Methods: We classified dominant graminoids into trait-based Plant Functional Types (PFTs) and simulated their long-term response to fertility, annual mowing and past ploughing. Results: Simulations demonstrated that a temporary dispersal limitation of long-lived tussock grasses could have allowed species-rich hay meadows to develop as alternative communities. We also show that when they are regularly mown, meadows are resistant to colonisation by long-lived tussock grasses. Conclusions: Our results thus support traditional management based on regular mowing, but also highlight the key role of landscape history through its effects on dispersal. Our study also demonstrates the usefulness of easy-to-measure plant traits and a widely applicable generic modelling framework for testing hypotheses on the long-term interactions of multiple drivers of vegetation dynamics.