Habitat fragmentation weakens the positive relationship between grassland plant richness and above-ground biomass

Abstract

Anthropogenic habitat fragmentation has been shown to be a major threat to global biodiversity and ecosystem function. However, little is known about how habitat fragmentation alters the relationship between biodiversity and ecosystem function (BEF relationship). Based on 130 landscapes identified using a stratified random sampling in the agro-pastoral ecotone of northern China, we investigated using a structural equation model the effects of habitat fragmentation (including habitat loss and fragmentation per se) on plant richness, above-ground biomass, and the relationship between them in grassland communities. We found that habitat loss decreased plant richness, while fragmentation per se increased plant richness. Fragmentation per se decreased above-ground biomass, while habitat loss had no significant effect on above-ground biomass. Neither habitat loss nor fragmentation per se affected the direction of the positive relationship between plant richness and above-ground biomass. However, habitat loss decreased the magnitude of the positive relationship by reducing the percentage of grassland specialists in the community. These results demonstrate that habitat loss and fragmentation per se have inconsistent effects on biodiversity and ecosystem function, with the BEF relationship being moderated by landscape context. Our findings emphasize that habitat loss rather than fragmentation per se can weaken the positive BEF relationship by decreasing the degree of habitat specialization of the community. BEF relationship is moderated by landscape context in fragmented landscapes. Habitat loss and fragmentation per se have inconsistent effects. Habitat loss can weaken the positive BEF relationship.