Tropical Understory Herbaceous Community Responds More Strongly to Hurricane Disturbance than to Experimental Warming

The Science

Herbaceous plants that were warmed 4°C in the understory of a tropical forest in Puerto Rico for a year to mimic future climate change showed little change in leaf cover or species composition. However, this herbaceous understory increased dramatically in leaf area after the forest overstory was disturbed by two hurricanes.

The Impact

These results show that warming may not be the most consequential short-term effect of climate change for tropical forest understories. Rather, the increase in climate extremes, such as hurricanes, are more likely to cause abrupt changes in tropical forest understories.

Summary

BER supported researchers studied the effects of experimental warming on the abundance and composition of a tropical forest floor herbaceous plant community in the Luquillo Experimental Forest, Puerto Rico. This study was conducted within Tropical Responses to Altered Climate Experiment (TRACE) plots, and used infrared heaters under free-air, open-field conditions, to warm understory vegetation and soils +4 °C above nearby control plots.  Results showed that one year of experimental warming did not affect the cover of individual herbaceous species, fern population dynamics, species richness, or species diversity.  After one year of the warming experiment, Hurricanes Irma and María damaged the heating infrastructure and opened up the forest overstory.  One year after this hurricane disturbance, when plots were not experimentally warmed, herbaceous plant cover increased from 20% to 70%, bare ground decreased from 70% to 6%, and species composition changed. The negligible effects of warming may have been due to the short duration of the warming treatment or an understory that is somewhat resistant to higher temperatures.

Principal Investigator

Deborah Kennard
Colorado Mesa University
[email protected]

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This work was supported by the U.S. Department of Energy Office of Science (DE-SC0012000 and DE-SC-0011806), NSF Award 1754713, the Luquillo Long-Term Ecological Research Program, and by the U.S. Geological Survey Ecosystems Mission Area. D.K. travel was supported by a CMU grant. The USDA Forest Service International Institute of Tropical Forestry (IITF) and University of Puerto Rico-Río Piedras provided additional support.

References