B52C-06
Ecosystem response to multiple drought events: the role of legacy effects
Friday, 18 December 2015: 11:35
2006 (Moscone West)
Melinda Smith1,2, David L Hoover3, Kevin R. Wilcox4, Andrew Jennings Felton5 and Alan Knapp1, (1)Colorado State University, Fort Collins, CO, United States, (2)Colorado State University, Graduate Degree Program in Ecology, Fort Collins, CO, United States, (3)USGS, Baltimore, MD, United States, (4)University of Oklahoma, Department of Microbiology and Plant Biology, Norman, OK, United States, (5)Colorado State University, Biology, Fort Collins, CO, United States
Abstract:
Climate extremes, such as drought and heat waves, are forecast to be more frequent and severe with climate change. As a consequence, such events will become increasingly important drivers of future ecosystem dynamics and function. We experimentally imposed two extreme growing season drought events in a central US grassland to assess the impacts of multiple droughts on ecosystem response and recovery dynamics. The first extreme drought (with growing season precipitation totals lower than the driest two year period of the 1930s US Dust Bowl)reduced aboveground net primary productivity (ANPP) below the lowest level measured in this grassland for almost thirty years. The extreme reduction in ecosystem function with the first two-year drought was a consequence of reduced productivity of the two dominant functional groups in this grassland - C4 grasses and C3 forbs. However, the most abundant (dominant) C3 forb was negatively impacted by the drought more than the dominant C4 grass. This differential sensitivity led to a reordering of species abundances within the plant community. Yet, despite this large shift in plant community composition, which persisted post-drought, ANPP recovered completely the year after drought. This rapid recovery in function was due to a rapid demographic response by the dominant C4 grass, which compensated for loss of the dominant C3 forb. Because of this shift in composition to greater C4 grass dominance, we expected that the second drought would have a greater impact on ecosystem function of plots that had not experienced drought. However, contrary to these expectations, previously droughted plots were more sensitive to drought than those plots that had not experienced drought. Thus, the legacy of drought (shift in community composition) made this grassland more sensitive to subsequent drought. Overall, our results suggest that low resistance of ecosystem function to an extreme climatic event does not preclude rapid ecosystem recovery. However, despite rapid recovery from drought, legacies of drought may increase sensitivity to future extreme events.
