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

BER Research Highlights


Climate Sensitive Size-Dependent Survival in Tropical Trees
Published: August 14, 2018
Posted: December 28, 2018

The Science
Tropical forests have very high species diversity that poses a significant challenge to our predictive understanding of tropical forest dynamics. Scientists from the NGEE-Tropics study found that tropical species were able to be classified into four survival modes, which explain life-history variation of survival that shapes carbon cycling under different climate conditions as measured by annual temperature and cumulative water deficit.

The Impact
The consistent survival modes identified across different tropical forests allow us to simulate the forest survival in a relatively small number of trackable functional types for hyper-diverse tropical forests within Earth System Models (ESMs). Frequently collected functional traits, such as wood density, leaf mass per area and seed mass, were not generally predictive of the survival modes of species. Mean annual temperature and cumulative water deficit predicted the proportion of biomass of survival modes, indicating important links between evolutionary strategies, climate, and carbon cycling.  As tree survival plays a key role in regulating vegetation dynamics, researchers expect that this analysis can provide insights to better simulate vegetation dynamics in ESMs.

Summary
Survival rates of large trees determine forest biomass dynamics. Survival rates of small trees have been linked to mechanisms that maintain biodiversity across tropical forests. How species survival rates change with size offers insight into the links between biodiversity and ecosystem function across tropical forests. Scientists from the NGEE-Tropics study tested patterns of size-dependent tree survival across the tropics using data from 1,781 species and over 2 million individuals to assess whether tropical forests can be characterized by size-dependent life-history survival strategies. They found that species were classifiable into four survival modes that explain life-history variation that shapes carbon cycling and the relative abundance within forests. Frequently collected functional traits, such as wood density, leaf mass per area and seed mass, were not generally predictive of the survival modes of species. Mean annual temperature and cumulative water deficit predicted the proportion of biomass of survival modes, indicating important links between evolutionary strategies, climate and carbon cycling. Their results reveal globally identifiable size-dependent survival strategies that differ across diverse systems in a consistent way.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov

Dorothy Koch
SC-23.1
Dorothy.Koch@science.doe.gov

(PI Contact)
Chonggang Xu, Los Alamos National Laboratory, cxu@lanl.gov and Nate McDowell, Pacific Northwest National Laboratory, nate.mcdowell@pnnl.gov

Funding
The first author Daniel Johnson was supported by Los Alamos National Laboratory (Director’s Post-doctoral Fellowship).  Contributions by Chonggang Xu, Jeff Chambers, Stuart David, and Nate McDowell were supported by the Next-Generation  Ecosystem Experiments (NGEE-Tropics) project, funded by the US Department of  Energy, Office of Biological and Environmental Research. Sean McMahon was partially funded by NSF - EF1137366. 

Publications
Johnson, D. J. et al. “Climate sensitive size-dependent survival in tropical trees.” Nature Ecology & Evolution 2, 1436-1442 (2018). [DOI:10.1038/s41559-018-0626-z]

Related Links
Tropical tree survival: the large and the small of it

Topic Areas:

  • Research Area: Earth and Environmental Systems Modeling
  • Research Area: Terrestrial Ecosystem Science

Division: SC-23 BER

 

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