Sustaining ecosystem services in ancient limestone grassland: importance of major component plants and community composition

Summary1 Limestone grasslands are among the most floristically rich ecosystems in northern Europe and have recently been shown to sustain ecosystem functioning under conditions of heavy nitrogen (N) deposition. Here we report a long‐term mesocosm experiment, designed to measure the importance of major component plants and community composition in providing ecosystem services (in particular preventing leaching of inorganic N). 2 A number of important steps were taken in the experimental design to increase conformity of the experimental communities to real limestone pasture, including using natural soils, plant cuttings of limestone grassland provenance and simulated management. Furthermore, communities were allowed to establish for 8 years before measurements were made. 3 Leaching of and were found to differ by up to a considerable two orders of magnitude according to functional group composition, with sedges and forbs leaching the most. Grass communities and communities containing all three functional groups (grasses, sedges and forbs) leached similarly low amounts of and . 4 Levels of soil and followed a similar pattern of inter‐community differences to leaching, while vegetation biomass and vegetation N stocks were very similar between communities consisting of only grasses, only sedges and the most species rich community (4 grasses + 4 sedges + 4 forbs). 5 Perennial grasses appeared to play the key role in inorganic N retention, with communities consisting of these plants having equally low leaching as more species rich communities. Indeed, most ecosystem services were performed comparatively well by grass communities as by the most species rich community. 6 No overall effects on provision of services resulted from mixing functional groups or increasing the number of species representing each functional group. 7 Synthesis . This work shows that more than order‐of‐magnitude differences in provision of ecosystem services can occur between species that coexist naturally in ancient limestone pasture. However, despite these large differences, because of the key role played by grasses, expected shifts in community composition anticipated as a result of N pollution may not impair the capacity of these systems to provide ecosystems services.