Ambient changes exceed treatment effects on plant species abundance in global change experiments

TitleAmbient changes exceed treatment effects on plant species abundance in global change experiments
Publication TypeJournal Article
Year of Publication2018
AuthorsJ. Langley, Adam, Chapman Samantha K., La Pierre Kimberly J., Avolio Meghan, Bowman William D., Johnson David S., Isbell Forest, Wilcox Kevin R., Foster Bryan L., Hovenden Mark J., Knapp Alan K., Koerner Sally E., Lortie Christopher J., Megonigal James P., Newton Paul C. D., Reich Peter B., Smith Melinda D., Suttle Kenwyn B., and Tilman David
JournalGlobal Change Biology
Date PublishedJun-10-2018
KeywordsELEVATED CO2, nitrogen, phosphorus, plant community, warming; water
Abstract

The responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long-term global change studies manipulating CO2 , nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species-level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species-level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long-term global change experiments yielding 2,116 experiment-species-treatment combinations. Surprisingly, for most species (57%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.

URLhttp://doi.wiley.com/10.1111/gcb.14442
DOI10.1111/gcb.14442
Short TitleGlob Change Biol