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Understanding the mechanisms behind tree responses to drought-induced stress with increasing tree size

Project description

The role of height in a tree’s response to drought

Trees adjust to drought conditions by reducing leaf transpiration and, in turn, sap flow, preventing extensive water loss and embolism. Tall trees are more sensitive to drought stress; however, the mechanisms behind this higher vulnerability are not yet fully understood. The DISTRESS project aims at looking at Darcy’s law of fluid flow to determine tree height’s influence on short- and long-term responses to drought. Through the analysis of different traits in tropical trees and sap flow data from 159 species from different biomes, DISTRESS will lead to a better understanding of tree vulnerability to drought and contribute to better simulations of the effect of climate change on forest ecosystems.

Objective

Plants adjust leaf water potential and hydraulic conductance under drought through stomatal behaviour, reducing sap flow and protecting plants from extensive water loss and embolism. Due to the negative effect that vapour pressure deficit (VPD) and tree height have on canopy-scale water conductance (G), Darcy’s law predicts a decline in G due to the expected increase in VPD following climate warming, to which tall trees would be presumably more sensitive. Further work is thus needed to understand the effect that tree size has on tree response to increased VPD and drought. This project aims at (1) testing whether, at a given VPD, trees adjust different functional traits to compensate for the negative effect of height on G in (a) tropical forests and (b) at a global scale, and (2) describing the mechanisms behind these adjustments and the potential interactions with other functional processes that may impair tree response to drought stress with increasing size. We will first measure multiple functional traits (including sap flux, gas exchange and leaf and xylem water potential) on trees of different heights to test Darcy’s law predictions and evaluate the role that the trade-offs among traits play on enhanced vulnerability to drought with increasing tree size in tropical forests. In order to assess whether the studied mechanisms prevail across species and ecosystems, we will perform a global-scale analysis of sap-flow and, thus, G responses to VPD as a function of tree height using the sap-flux data from 159 species and nine different biomes gathered within SAPFLUXNET. This integrated analysis will provide a better understanding of the role that tree size plays in tree vulnerability to drought in the short (temporary physiological response) and long term (legacy effects), allowing the improvement of mechanistic models of tree response to climatic variability. Such information is essential to better simulate the impact that climate change may have on forest ecosystems.

Coordinator

CENTRO DE INVESTIGACION ECOLOGICA Y APLICACIONES FORESTALES
Net EU contribution
€ 245 732,16
Address
UNIVERSITAT AUTONOMA DE BARCELONA EDIFICI C
08193 Bellaterra
Spain

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Region
Este Cataluña Barcelona
Activity type
Research Organisations
Links
Total cost
€ 245 732,16

Partners (1)