Increasing plant species richness by seeding has marginal effects on
ecosystem functioning in agricultural grasslands
Abstract
Experimental evidence shows that grassland plant diversity enhances
ecosystem functioning. Yet, the transfer of results from controlled
biodiversity experiments to naturally assembled ‘real world’ ecosystems
remains challenging. Here, we address this issue by experimentally
sowing locally absent plant species in 73 agricultural grasslands along
a land-use intensity gradient, to test how ecosystem functions related
to productivity and nutrient cycling respond to species enrichment. We
found that only one of 12 ecosystem functions responded to changes in
species richness. In fact, ecosystem functioning was rather driven by
environmental conditions and land-use intensity. This suggests that the
functionally-relevant niche space is saturated in naturally assembled
grasslands, and that competitive, high-functioning species are already
present. While nature conservation and cultural ecosystem services
certainly benefit from species enrichment, our study indicates that
plant species enrichment may deliver only weak increases in ecosystem
functioning in both moderately intensive and traditionally managed
agricultural grasslands.