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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Ecological Role of Hydraulic Traits of Amazon Rainforest Trees

Thomas L. Powell
Lawrence Berkeley National Laboratory

Highlight

18 May 2017

Differences in xylem and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees

The Science 
This study demonstrated that tropical tree species that were tolerant of an experimental drought had hydraulic traits that differed from those that were intolerant.  The hydraulic traits of the measured species were not aligned with their early- versus late-successional life histories, thus revealing an important drought-tolerance control over tropical forest dynamics.

The Impact
The observed differences in plant hydraulic traits enhances our understanding of important controls over tropical forest dynamics, which is critical for informing the parameterization of hydrodynamic formulations used in Earth System Models.

Summary
This study found a characteristic pattern in the measured leaf and xylem traits of several tropical tree species that was consistent with their demographic responses to an experimentally-imposed drought.  This study provides valuable insight into the traits controlling drought tolerance of tropical rainforest trees and provides much needed information for parameterizing more realistic water-stress functions in Earth System Models. Finally, understanding the variability in plant hydraulic traits that exists among tropical tree species is critical for determining the fate of the Amazon rainforest if precipitation patterns change substantially.

Contacts (BER PM)
Daniel Stover and Dorothy Koch
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289); dorothy.koch@science.doe.gov (301-903-0105)

(PI Contact)
Thomas L. Powell
Lawrence Berkeley National Laboratory
tlpowell@lbl.gov

Funding
This research was funded by a National Science Foundation Doctoral Dissertation Improvement Grant (NSF award # DEB-1110540), the National Science Foundation Partnership for International Research and Education in Amazon Climate Interactions grant (NSF award #OISE-0730305), a grant from the Andes-Amazon Initiative of The Gordon and Betty Moore Foundation, graduate research funding from the Department of Organismic and Evolutionary Biology, Harvard University, and the Office of Biological and Environmental Research, US Department of Energy, NGEE-Tropics grant.  Patrick Meir was supported by NERC NE/J011002/1 and ARC FT110100457.

Publications
Powell T.L., Wheeler J.K., de Oliveira  A.A.R., da Costa A.C.L., Saleska S.R., Meir P., Moorcroft P.R. Differences in xylem cavitation resistance and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees. Global Change Biology (2017). DOI: 10.1111/gcb.13731

Powell T., Moorcroft P. Leaf Pressure Volume Data in Caxiuanã and Tapajós National Forest, Para, Brazil (2011). NGEE Tropics Data Collection. Accessed at http://dx.doi.org/10.15486/NGT/1347606

Powell T., Moorcroft P. Xylem vulnerability curves of canopy branches of mature trees from Caxiuanã and Tapajós National Forests, Para, Brazil. NGEE Tropics Data Collection. Accessed at http://dx.doi.org/10.15486/NGT/1347607


Example of how one of the measured hydraulic traits, turgor loss point (TLP), differs substantially between the drought-tolerant and drought-intolerant plant functional types. Once drought-tolerance is accounted for, TLP does not differ spatially between different Amazon sites (Tapajós (TNF) versus Caxiuanã (CAX) National Forests, Brazil), or between successional types (early versus late). The plant species are defined as follows, IS: Inga species, early-successional drought-intolerant, EC: Eschweilera coriacea, late-successional drought-intolerant. PS: Protium species, early-successional drought-tolerant. LS: Licania species, late-successional drought-tolerant.

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