October 09, 2018

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Crown Damage and the Mortality of Tropical Trees

A study on crown damage, growth, and survival in a tropical forest in Borneo.

The Science

Tree death is the result of interactions between factors, including direct and indirect effects. Crown damage and previous growth mediated most of the effect of tree size, wood density, soil fertility, and habitat suitability on mortality.

The Impact

Crown damage and individual growth (growing more or less than typical for the species) are very important. Habitat is important because fertility and moisture influence individual growth, more than influencing mortality of trees inside or outside their preferred habitat.

Summary

What causes individual tree death in tropical forests remains a major gap in the understanding of the biology of tropical trees and leads to significant uncertainty in predicting global carbon cycle dynamics. Scientists from the Next-Generation Ecosystem Experiments (NGEE)–Tropics study and the Smithsonian Tropical Research Institute measured individual characteristics (diameter at breast height, wood density, growth rate, crown illumination, and crown form) and environmental conditions (soil fertility and habitat suitability) for 26,425 trees = 10 cm diameter at breast height belonging to 416 species in a 52-hectare (ha) plot in Lambir Hills National Park, Malaysia. They used structural equation models to investigate the relationships among the different factors and tree mortality. Crown form (a proxy for mechanical damage and other stresses) and prior growth were the two most important factors related to mortality. The effect of all variables on mortality (except habitat suitability) was substantially greater than expected by chance. Tree death is the result of interactions between factors, including direct and indirect effects. Crown form or damage and prior growth mediated most of the effects of tree size, wood density, fertility, and habitat suitability on mortality. Large-scale assessment of crown form or status may result in improved prediction of individual tree death at the landscape scale.

Principal Investigator

Stuart Davies
Smithsonian Environmental Research Center
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

The Lambir 52-ha plot was established as a collaboration between the Forest Department of Sarawak, Malaysia, Harvard University [National Science Foundation (NSF) awards DEB-9107247 and DEB-9629601), and Osaka City University (grants 06041094, 08NP0901, and 09NP0901). The research has been supported by the Asia program of the Arnold Arboretum (Harvard University), the Center for Tropical Forest Science–Forest Global Earth Observatory of the Smithsonian Tropical Research Institute, and NSF award DEB-1545761 to S.J.D.  G.A. and S.J.D. were supported as part of the Next-Generation Ecosystem Experiments (NGEE)–Tropics, funded by the Office of Biological and Environmental Research (BER) within the U.S. Department of Energy Office of Science.

References

Arellano, G., N.G. Medina, S. Tan, and M. Mohamad, et al. "Crown damage and the mortality of tropical trees". New Phytologist 221 (1), 169–179  (2018). https://doi.org/10.1111/nph.15381.