Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2009
Publication Date: 4/9/2009
Citation: Isbell, F.I., Polley, H.W., Wilsey, B.J. 2009. Biodiversity, productivity and the temporal stability of productivity: Patterns and processes. Ecology Letters. 12:443-451.
Interpretive Summary: Plants are the foundation of all life on Earth, providing food that is consumed either directly or indirectly by humans and animals. We must better understand how to maximize plant growth or production while reducing year-to-year variability in plant production if we are to support an ever-expanding human population. It has been suggested that we may both increase the amount of plant material that is produced and reduce the variability of that production among years by increasing the number of plant types (plant species) that are present in grasslands and other plant communities. We established grassland plants in various combinations in field plots in central Texas to determine whether the amount of plant production and its variability among years depended on the number of plant species in each plot. The amount of plant material produced each year varied less among years in plots planted with more species. Production in plots with more species was more stable from year to year partly because species responded differently to year-to-year changes in weather. Years during which some species grew poorly were years during which other species grew well. Increasing the number of plant species in each 1 meter by 1 meter plot from 1 to 4 species also increased overall plant production. Our results indicate that we may both increase the amount of plant material produced and reduce variability in plant production among years by increasing the number of plant species present in grasslands that currently contain few species.
Technical Abstract: Theory predicts that the temporal stability of productivity, measured as the ratio of the mean to the standard deviation of community biomass, increases with species richness and evenness. We used experimental species mixtures of grassland plants to test this hypothesis and identify the mechanisms involved. Additionally, we tested whether biodiversity, productivity, and temporal stability were similarly influenced by particular types of species interactions. We found that productivity was less variable among years in plots planted with more species. Temporal stability did not depend on whether the species were planted equally abundant (high evenness) or not (realistically low evenness). Greater richness increased temporal stability by increasing overyielding, the asynchrony of species fluctuations, and statistical averaging. Species interactions that favored unproductive species increased both biodiversity and temporal stability. Species interactions that resulted in niche partitioning or facilitation increased both productivity and temporal stability. Thus, species interactions can promote biodiversity and ecosystem services.