The Science

Forest mortality has overriding control on the forest carbon cycle. However, the drivers of mortality in forests are not well understood, and are consequently not well represented in Earth system models. This study develops a method for assessing how trees die and how mortality rates differ among species, size classes, and functional groups. The new method will capture rare mortality events and detect mortality events that may be linked to environmental change.

The Impact

The scientists use four censuses of a 25.6-ha ForestGEO forest dynamics plot to assess mortality patterns. With such a large sample size it is possible to characterize mortality rates by size, species, plant functional type, and microhabitat, allowing for detailed understanding of the drivers of mortality. The method developed forms the basis of a protocol now being applied at 10 large-scale tropical ForestGEO plots under the Next-Generation Ecosystem Experiments (NGEE)–Tropics project.

Summary

Since understanding fine-scale mortality processes is essential for modeling forest responses to changing climatic and environmental conditions, this work makes important progress in providing empirical observations that will inform future modeling activities in the NGEE-Tropics project. Furthermore, widespread application of annual tree mortality surveys on large forest dynamics plots will provide greater insights into the annual variability of forest structural and compositional changes that result from tree death associated with anthropogenic, ecological, or climatic disturbances.

Principal Investigator

Stuart Davies
Smithsonian Tropical Research Institute
daviess@si.edu

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

Funds for the full tree censuses were provided by the Smithsonian Institution Center for Tropical Forest Science–Forest Global Earth Observatory (CTFS-ForestGEO). Annual mortality censuses and the analyses presented here were funded by a Smithsonian Competitive Grants Program in Science award to KAT. CYE received support from the Mary Jean Hale Fund. SJD received support from the Next-Generation Ecosystem Experiments (NGEE)–Tropics project.

References