Modeling tree water deficit from microclimate: an approach to quantifying drought stress
R Zweifel1, L Zimmermann, D M Newbery
1Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland. roman.zweifel@ips.unibe.ch
Tree Physiology
|December 3, 2004
Summary
Tree water deficit (DeltaW) closely matches model estimates (DeltaWE) driven by soil water potential and atmospheric vapor pressure deficit. This indicates trees cannot maintain a specific water deficit, with environmental factors being the primary drivers.
Area of Science:
- Plant physiology
- Forest ecology
- Environmental science
Background:
- Tree water deficit is a critical factor influencing forest health and productivity.
- Accurate estimation of tree water deficit is essential for understanding drought stress and ecosystem responses.
- Previous methods for estimating tree water deficit have limitations in capturing dynamic environmental influences.
Purpose of the Study:
- To compare tree water deficit estimated from stem radius changes (DeltaW) with model-driven estimates (DeltaWE).
- To investigate the influence of soil water potential (Psisoil) and atmospheric vapor pressure deficit (VPD) on tree water deficit.
- To assess the applicability of a physiological model for estimating tree water deficit across different species and sites.
Main Methods:
- Measured stem radius changes using dendrometers to estimate DeltaW, detrending for growth.
- Developed and applied a model (DeltaWE) using Psisoil and VPD as inputs.
- Monitored DeltaW and DeltaWE in *Pinus sylvestris*, *Quercus pubescens*, and *Picea abies* at dry and wet sites in the Swiss Alps.
Main Results:
- Seasonal courses of DeltaW were similar across species and sites, largely explained by DeltaWE.
- A model incorporating both Psisoil and VPD provided better estimates of DeltaW than either factor alone.
- Species-specific differences in DeltaW were partially explained by varying weighting of Psisoil against VPD.
Conclusions:
- Tree water deficit is primarily driven by a combination of soil and atmospheric conditions, not maintained at a specific level by the tree.
- The developed model (DeltaWE) shows promise for estimating tree water deficit in various tree species.
- Understanding the interplay between soil moisture and atmospheric demand is crucial for predicting tree responses to water stress.
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