Global change effects on plant communities are magnified by time and the number of global change factors imposed

Authors: KOMATSU, KIMBERLY - Smithsonian Environmental Research Center; AVOLIO, MEGHAN - Johns Hopkins University; LEMOINE, NATHAN - Marquette University; ISBELL, FOREST - University Of Minnesota; GRMAN, EMILY - Eastern Michigan University; HOUSEMAN, GREGORY - Wichita State University; KOERNER, SALLY - University Of North Carolina Greensboro; JOHNSON, DAVID - Virginia Institute Of Marine Science; WILCOX, KEVIN - University Of Wyoming; ALATALO, JUHA - Qatar University; ANDERSON, JOHN - New Mexico State University; AERTS, RIEN - Vrije University; BAER, SARA - Southern Illinois University; Bates, Jonathan - Jon

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2019
Publication Date: 8/19/2019
Citation: Komatsu, K.J., Avolio, M.L., Lemoine, N.P., Isbell, F., Grman, E., Houseman, G.R., Koerner, S.E., Johnson, D.S., Wilcox, K.R., Alatalo, J.M., Anderson, J.P., Aerts, R., Baer, S.G., Bates, J.D., et al. 2019. Global change effects on plant communities are magnified by time and the number of global change factors imposed. Proceedings of the National Academy of Sciences. 116(36):17867-17873. https://doi.org/10.1073/pnas.1819027116.
DOI: https://doi.org/10.1073/pnas.1819027116

Interpretive Summary: Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (=10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

Technical Abstract: Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. In a global synthesis of over 100 experiments we found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y), but in long-term (=10 y) experiments show increasing community divergence of treatments from control conditions. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.