From Grasslands to Forblands: Year‐round grazing as a driver of plant diversity

Abstract Grazing by domestic herbivores is applied across Europe to combat the loss of light‐dependent, species‐rich communities due to encroachment by competitive woody and herbaceous plants. However, the billions of euros spent annually by the EU on grazing subsidies have failed to halt the loss of species in open habitats. We hypothesized that typical agri‐environmental, seasonal grazing fails to simulate the ecological effects of now‐extirpated, large, wild herbivores, which coevolved with these species‐rich communities. We conducted a survey of 30 semi‐natural sites, where grazing was either absent, seasonal, or year‐round, across a spectrum of abiotic conditions. We recorded plant species diversity and cover and used plant traits to assess taxonomic and functional responses. Year‐round grazing supported higher plant species richness and forb cover compared to seasonal or no grazing. Specifically, dormant‐season (winter) grazing pressure increased species richness and forb cover, superseding additional effects of growing‐season (summer) grazing pressure. Functional richness was similar across management types, likely due to higher plant trait similarity in year‐round grazed sites. Our results support that dormant‐season grazing plays a key role in weakening interspecific competition among plants and in enabling diverse forb communities to replace species‐poor grass dominance. Synthesis and applications . Our results indicate that typical, seasonal grazing may be counterproductive in terms of promoting plant diversity. We found the most effective management strategy for conserving species‐rich forb communities to be year‐round grazing. Our results urge a greater focus on the ecological and evolutionary mechanisms behind the relationship between large herbivores and plants, not least the balance between grasses and forbs. We advocate a shift in conservation strategies towards natural grazing, to halt the continued loss of species that depend on open and semi‐open, forb‐rich habitats such as grasslands, wetlands, and woodlands.