Functional anatomy and water transport strategies of rainforest plants

Abstract

Tropical rainforests are key terrestrial ecosystems involved in the maintenance of earth’s biodiversity and carbon budget but are sensitive to climate change. Because rainforests typically occur in environments of high rainfall, climate change induced drought events is likely to result in extensive plant mortality, resulting in shifts of community composition and stand biomass. Lowland tropical rainforests are of particular concern, as their vulnerability to drought is still not well understood. How species in these rainforests will cope with such droughts will dependent, among others factors, on the strategies that these plants use to transport water. Based on that, I adopted both a species- and ecosystem-level approaches in this thesis to study hydraulic-related functional traits of plants. The structure of my thesis is as follows - the first part consists of a general introduction and literature review, and the second part consists of two articles (one published and the other in revision) pertaining to my research. These studies were developed during two years of an internship resulted from a collaboration between Federal University of Lavras, Brazil, and James Cook University, Australia, and were conducted in tropical lowland rainforest in Daintree National Park, northeast Australia. In the first manuscript, I used a multidisciplinary approach involving vegetation ecology, plant physiology and anatomy to conduct a study on water use strategies of eight species of rainforest trees. In the second manuscript, I investigated how wood traits relates to leaf water use efficiency across 90 plant species in six functional groups (Maturephase trees, Understorey trees and –shrubs, Pioneer trees and –shrubs, and vines). Overall, my results suggest that different plant functional groups exhibit various contrasting water use strategies, and also that leaf-level physiological processes and wood anatomy are coordinated. Models for predicting changes in vegetation during climate change scenarios can benefit from a biophysical approach involving the use of wood and leaf anatomical trait data combined with physiological measurements (i.e. sap flow rates, intrinsic water-use-efficiency). Such integrated approaches are becoming increasingly useful for contextualizing plants responses to drought, particularly for species-rich ecosystems such as tropical lowland rainforests.