Abstract
To improve projections of consequences of increasing intensity and frequency of drought events for grasslands, we need a thorough understanding of species performance responses to drought, of performance trade-offs and how drought resistance is related to species distributions. However, comparative and quantitative assessments of whole-plant drought resistance that allow to rigorously address these aspects are lacking for temperate grassland species. We conducted a common garden experiment with 40 common temperate grassland species to compare species survival and growth under intense drought and well-irrigated conditions. Overall, survival and growth were significantly reduced under drought, with the effect varying across species. Species ranking of drought damage and survival remained consistent with progressing drought. No performance trade-offs emerged between optimal growth and drought resistance of survival (‘growth–stress tolerance’ trade-off hypothesis), or between growth under well-watered and dry conditions (‘growth rates’ trade-off hypothesis). Species local- and large-scale association with moisture (Ellenberg F value and rainfall niche) was not related to their drought resistance. Overall, our results imply that trade-offs and differences of species fundamental drought resistance are not the main drivers of hydrological niche differentiation, species coexistence and their distribution across moisture gradients. The comparative experimental assessment of species whole-plant drought responses we present provides a basis to increase our understanding of current grassland responses to variation of moisture regimes and for projecting consequences of future changes.
Highlights
Drought is an important driver of community composition, diversity, and ecosystem function in a variety of ecosystems worldwide
We focused the analyses on relative growth rates (RGR) of surviving individuals, i.e., the individuals that will contribute to future population dynamics
High survival and positive growth under the drought in most species indicate that many species in temperate grasslands are well adapted to even intense drought conditions
Summary
Drought is an important driver of community composition, diversity, and ecosystem function in a variety of ecosystems worldwide. In a wide range of temperate grasslands, drought decreases productivity and influences species abundance and distribution, as well as community composition and diversity patterns (Tilman and El Haddi 1992; Buckland et al 1997; Knapp et al 2002). The response and resilience of grasslands to drought are influenced by community composition and diversity (Tilman and Downing 1994; Isbell et al 2015). I.e., their ability to withstand periods of low water availability, varies widely, and species segregate across moisture gradients even within grassland communities (Buckland et al 1997; Silvertown et al 2015). The intensity and frequency of drought events are expected to increase
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