For over a half century, ecologists have debated the effects of plant diversity on the stability of ecosystems. Recent studies have found that plant diversity increases stability of biomass for the entire plant community, even as it slightly reduces the stability of biomass of individual plants species. Working with a diverse arthropod community of over 700 species and over 100,000 individuals in a large, decade long experiment with simple to diverse plots, we asked: Does the stabilizing effect of plant diversity on plant communities propagate up consumer foodwebs to herbivore and predator trophic levels? We considered temporal stability, or the temporal fluctuation in diversity or abundance measured as the inverse coefficient of variance.
Results/Conclusions
We found that plant diversity stabilizes the diversity and total abundance of arthropods at the herbivore and predator trophic levels. Similar to what has been found for plant biomass, plant diversity stabilizes the arthropod community as a whole, while reducing the stability of individual populations of insect herbivores. Specifically, higher plant diversity reduced stability of most specialist, but not of generalist, insect herbivores. Our results can be explained by plant diversity and factors affected by it, namely the biomass and stability of plant populations and communities. Conversely, arthropod stability cannot be explained by top-down factors. Taken together, our results show that plant diversity stabilizes entire food webs. This stability, combined with reduced herbivore abundances in more plant diverse plots, suggests that higher plant diversity in habitats adjacent to agricultural crops or in fields dedicated to biofuels may serve to increase biological control and reduce outbreaks of insect pests.