2018 ESA Annual Meeting (August 5 -- 10)

SYMP 4-2 - Ecological responses to extreme climatic events: Linking theory, observations, and experiments

Tuesday, August 7, 2018: 8:30 AM
350-351, New Orleans Ernest N. Morial Convention Center
David L. Hoover1, Melinda Smith2, Alan Knapp2, Kevin Wilcox1, Kristina E. Young3, Meghan L. Avolio4, Sally E. Koerner5 and Kimberly J. La Pierre6, (1)Rangeland Resources and Systems Research Unit, USDA-ARS, Fort Collins, CO, (2)Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, (3)Biological Sciences, University of Texas at El Paso, El Paso, TX, (4)Department of Earth & Planetary Sciences, Johns Hopkins University, MD, (5)Department of Biology, University of North Carolina Greensboro, Greensboro, NC, (6)Smithsonian Environmental Research Center, Edgewater, MD
Background/Question/Methods

Extreme climatic events are one of the most salient manifestations of climate change. Recent advances in event attribution has enabled quantitative statements about the extent climate change has influenced the magnitude or likelihood of extreme climatic events. However, as the relationship between anthropogenic climate change and extreme events gains clarity, the linkage between these events and ecological responses remains uncertain, as not all extreme events elicit extreme ecological responses. Theory predicts that extreme ecological responses will occur if an event pushes key organisms beyond critical thresholds, leading to changes in community composition and potentially prolonged recovery in ecosystem function. In this symposia, we will link theory to observed and experimentally imposed climate extremes using three studies. First, in a field experiment imposing heat waves and drought in a native grassland, we will use long-term climate and ecological data to place the extremity of climate drivers and ecological responses in historical context. Second, we will examine the resistance and resilience of productivity to the 2012 Central US drought across several ecosystem types with a focus on how community dynamics influenced ecosystem responses. Finally, using 89 published drought experiments, we will assess potential methodological issues in experimentation that may obfuscate patterns of drought sensitivities across ecosystems.

Results/Conclusions

In the field experiment, while drought and heat waves treatments were both climatically extreme, the ecosystem was resistant to heat waves but not extreme drought, as productivity dropped below the 5th percentile under extreme drought. The large drop in productivity was largely due to mortality of the dominant forb, yet contrary to theory, the productivity completely recovered one year following drought, despite a large shift in community composition. Similarly, across several ecosystems in the Central US, recovery from the 2012 drought was often rapid, despite some changes in community composition. Both observed and experimental responses to drought suggest that ecosystems can have low resistance but high resilience to short-term, extreme drought and that community reordering may not portend loss in ecological function. Finally, based on the literature, some of the variance in responses across drought experiments may be methodological, due to the co-varying nature of the control and treatments interacting with precipitation variability. Thus understanding ecological responses to extreme drought may be further complicated by the design of experiments. Overall, these results highlight some of the approaches and challenges in linking ecological responses to extreme climatic events.