U.S. Department of Energy Office of Biological and Environmental Research

PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Will Seasonally Dry Tropical Forests Be Sensitive or Resistant to Future Changes in Rainfall Regime?

Jennifer Powers
University of Minnesota

Highlight

Lysiloma divaricatum trees in Palo Verde National Park, Costa Rica, which died following the El Niño Southern Oscillation of 2015 that resulted in extremely low rainfall.  Photo by Jennifer Powers.

12 October 2017

A review of scientific literature on responses of seasonally dry tropical forests to changing rainfall.

The Science 
Seasonally dry tropical forests experience periodic droughts that occur each year but it is unknown how their organisms and ecosystem processes will respond to increasing climatic variability including extreme droughts and/or changes in the timing, duration or magnitude of rainfall regimes. This uncertainty has led to two very different predictions: some people argue that seasonally dry tropical forests will be very sensitive to changes in rainfall because they are already at hydrologic thresholds, while others claim that they will be resistant because these species are already adapted to strong seasonal drought. This paper reviewed existing studies with the goals of searching for general patterns that could discriminate between these two hypotheses and also to identify gaps in the literature to guide future research.

The Impact
This review found that there are many potential ways for “drought” to be manifested in seasonally dry tropical forests. Importantly, most of the studies are consistent with the prediction that changing rainfall regimes will have large effect on species composition and ecological function of these forests.

Summary
By the end of the 21st century, climate models predict substantial changes in rainfall regimes across the seasonally dry tropical forest biome, but little is known about how dry forests will cope with the hotter, drier conditions predicted by climate models. We explored two alternative hypotheses: 1) dry forests will be sensitive to drought because they are already limited by water and close to hydrologic thresholds, or 2) they will be resistant/resilient to intra- and inter-annual changes in rainfall because they are adapted to predictable, seasonal drought. In our review of literature spanning microbial to ecosystem scales, most studies suggests that increasing frequency and intensity of droughts in dry forests will likely alter species distributions and ecosystem processes. Though we conclude that dry forests will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast dry forest responses to future climate change at coarser spatial and temporal scales.

Contacts (BER PM)
Jennifer Powers
University of Minnesota, Departments of Ecology, Evolution, and Behavior and Plant and Microbial Biology, 1479 Gortner Ave, St. Paul, MN 55108
powers@umn.edu

(PI Contact)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

Funding
We thank the US Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program under award number DE-SC0014363 for funding. JSP also thanks the US National Science Foundation CAREER Award DEB-1053237.

Publications
Allen, K. et al. Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes? Environmental Research Letters 12, 023001 (2017). doi:doi.org/10.1088/1748-9326/aa5968.

University of Minnesota and Notre Dame University.

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