COS 21-5
Erosion of beta diversity under interacting global change impacts in a semiarid grassland
Human impacts are often thought of as homogenizing natural communities, but it is unclear how interacting impacts alter the beta diversity (spatial variability) of plant communities. In a grassland with high beta diversity along a soil fertility gradient, we asked which combinations of nutrient enrichment, precipitation enhancement, and disturbance would allow species to expand their distributions across the gradient; what plant traits would mediate species responses; and how beta diversity would change as a result. To alleviate dispersal limitation as a constraint on treatment responses, we added seeds of 15 species originating from different parts of the soil fertility gradient to our 132 plots.
Results/Conclusions
Fertilization and water addition permitted species from fertile soils to invade infertile soils, an effect that strengthened with time. Disturbance allowed species from infertile soils to transiently invade fertile soils. Plant height and exotic/native status best predicted the abilities of species to invade harsh habitats under ameliorated conditions. Among-habitat beta diversity of seeded species was reduced by fertilization and the joint treatment of fertilization and watering, although not by watering alone. Our findings are a novel demonstration of how interacting global change factors affect the biotic and abiotic resistances that control species’ invasions along a soil fertility gradient and thereby maintain beta diversity.