Biodiversity promotes resistance but dominant species shape recovery of grasslands under extreme drought

Manuele Bazzichetto, Marta Gaia Sperandii, Caterina Penone, Petr Keil, Eric Allan, Jan Lepš, Daniel Prati, Markus Fischer, Ralph Bolliger, Martin Gossner, Francesco de Bello

1. How biodiversity underpins ecosystem resistance (i.e., ability to withstand environmental perturbations) and recovery (i.e., ability to return to a pre-perturbation state) and thus stability under extreme climatic events is a timely question in ecology. To date, most studies have focused on the role of taxonomic diversity, neglecting how community functional composition and diversity beget stability under exceptional climatic conditions. In addition, land use potentially modulates how biodiversity and ecosystem functions respond to extreme climatic conditions.

2. Using an 11-year time-series of plant biomass from 150 permanent grassland plots spanning a gradient of land-use intensity, we examined how taxonomic and functional components of biodiversity affected resistance and recovery of biomass under extreme drought.

3. The association between biodiversity, land use, and biomass varied across years, especially in the driest years. Species rich or functionally diverse communities (associated with low land-use intensity) buffered extreme droughts better, while species poor communities or those dominated by fast-growing species (associated with high land-use intensity) had higher recovery capabilities after a moderate-to-extreme drought.

Synthesis. Our results show that plant community functional and taxonomic components determine grasslands resistance and recovery under moderate-to-extreme drought. In turn, this points to the importance of designing landscapes with both extensively and intensively managed grasslands. Functionally or taxonomically rich communities (favoured under low land-use intensity) would preserve biomass under extreme droughts, whereas species-poor or fast-growing communities (favoured by high land-use intensity) would restore biomass after extreme droughts.