Palms: A Model System for Evaluating Hydraulic Costs of Plant Size

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Award Abstract for Nathan G. Phillips Palms: A Model System for Evaluating Hydraulic Costs of Plant Size What are the limits to tree height? This question is both of fundamental interest to biologists, and to those interested in the management of forestry and carbon sequestration. This research will focus on water transport that is one of several key factors that may constrain tree height. The physics and biology underlying hydraulic costs of tree height are complex, and therefore not well understood, because the branching architecture in most tree species ramifies the water stream into innumerable flow paths. In addition, complex branching distributes foliage in multi-faceted layers adding further complexity. The goal of this research is to simplify the problem of assessing hydraulic costs of tree height by using the columnar palm as a simple model of hydraulic tree structure. The research with palms will take place at the Tiputini Research Station in Ecuador. The structural traits of the columnar palms allow analysis of water use in trees without branches. Palm trees consist of a solitary pipeline that supplies water to a distinct and compact crown of leaves. Measurements will characterize water flow through palms that vary in height, up to their maximum. Modeling of integrated impacts of water limitation on growth during the three-year research project will clarify understanding of the relative strengths of six specific mechanisms that incur costs for water transport and potentially limit vertical height growth in trees. Fundamental biophysical processes of the water transport will be examined in this research, resulting in the project improving understanding of water use by most tree species. The project includes broader impacts that promote international scientific cooperation and exchange between Ecuadorian and U.S. undergraduate students. In addition, the project provides a scientific basis for the economic and social use of the palms throughout Amazonia, which are estimated to be second only to grasses in economic importance. Finally, the project will contribute to continuing NSF support for undergraduate educational activities and research training at the Tiputini Biodiversity Station.