Land use conversion weakens the cascading effects of plant diversity on temporal stability of high trophic levels at multiple spatial scales in grasslands

Land use intensification is known to imperil biodiversity and ecosystem stability, while the effects of land use conversion on the stability of multiple trophic levels at multiple spatial scales, particularly the linkages between plant diversity and the temporal stability of biomass at high trophic levels, remain to be elucidated. We conducted a 4year field investigation to quantify the temporal stability of biomass for plants and herbivory, predatory, and omnivorous beetles at the species (population stability), community (alpha stability), and among communities (gamma stability) levels as natural grasslands convert to managed grasslands. We found local communities in natural grasslands exhibited greater asynchronous dynamics among species due to high plant diversity, but exhibited more stable population dynamics in managed grasslands, resulting in similar alpha stability and then gamma stability along the land use intensification gradients. Land use conversion decreased the alpha and gamma stability of predators by decreasing asynchronous dynamics among species and communities, respectively, and then decreased beetle alpha and gamma stability. Importantly, our results revealed that plant diversity enhanced the temporal stability of biomass at higher trophic level through the biodiversity cascading effects among trophic levels, but these effects were weakened as natural grasslands convert to managed grasslands. Our findings demonstrate that the negative effects of land use change on temporal stability relies on trophic levels but not spatial scales, and highlight that land use intensification decouples the links between plant diversity and the stability of biomass at higher trophic levels.