Effects of biodiversity loss and disturbance on the survival and performance of two Ranunculus species with differing clonal architectures

Seedlings of Ranunculus repens and R. acris were transplanted into an array of experimental grasslands with differing plant species richness and number of functional groups. Half of the plots were also subjected to simulated horse trampling, to examine how the interrelationship between diversity and disturbance affected the survivorship, growth and biomass of the Ranunculus transplants. Survivorship increased with increasing initial size of individuals or decreasing species richness of the plots. Vegetative growth, reproduction and aboveground biomass were strongly enhanced in response to a log-linear loss of species richness and secondarily by a decline in the number of functional groups. Disturbance had no effect on performance of transplants with one exception, ramet formation of R. acris, which was enhanced under the trampling regime. Despite differences in clonal architecture, both Ranunculus species behaved similarly. Our results demonstrate the importance of species richness in controlling invasibility of grassland communities.