Skip to main content
ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #296740
Title: Invaded grassland communities have altered stability-maintenance mechanisms but equal stability compared to native communities

Author
item WILSEY, BRIAN - Iowa State University
item DANESHGAR, PEDRAM - Monmouth University
item HOFMOCKEL, KIRSTEN - Iowa State University
item Polley, Herbert

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2013
Publication Date: 1/2/2014
Publication URL: http://handle.nal.usda.gov/10113/59494
Citation: Wilsey, B.J., Daneshgar, P.P., Hofmockel, K., Polley, H.W. 2014. Invaded grassland communities have altered stability-maintenance mechanisms but equal stability compared to native communities. Ecology Letters. 17:92-100.

Interpretive Summary: Plant communities are considered to be stable when biomass production varies little among years. Stability often is greater in communities with many than few plant species, but community stability is disproportionately influenced by the properties and growth patterns of dominant species. We compared stability of species-rich native plant communities with that of species-poor communities of non-native or exotic plants. We tested whether stability is being reduced by the decline in species richness that is occurring as native species are replaced by exotics. Native combinations of species exhibited many of the characteristics typically associated with stable communities – species grew at different times of years and were more productive when growing with other native species than with individuals of the same species. However, native and exotic communities did not differ in biomass stability over five years because the species that strongly dominated exotic assemblages were more stable than other exotic species. Native and exotic communities exhibited similar stability but were stabilized by different mechanisms. Exotic communities may be particularly vulnerable to herbivores, pests, or other agents that severely damage dominant species.

Technical Abstract: Theory predicts that stability should increase with diversity via several mechanisms. We tested predictions in a five-year experiment with exotic and native plant mixtures under two irrigation treatments. Diversity declined faster after planting in exotic than native mixtures. Variation in biomass across years (CV) was 50% lower in mixtures than monocultures of both native and exotic species. Growth among species was more asynchronous and overyielding values were greater during and after an unprecedented drought in 2011 in native than exotic mixtures. Mean-variance slopes indicated strong portfolio effects in both community types, but the intercept was higher for exotics than for natives, suggesting that exotics were inherently more variable than native species. However, this failed to result in higher CV’s in exotic communities because species that heavily dominated plots tended to have lower than expected variance. Results indicate that diversity-stability mechanisms are altered in invaded systems compared to native ones they replaced.