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Published on: June 20, 2019
Xylem as the main origin of stem radius changes in Eucalyptus
Roman Zweifel1, David M Drew2, Fritz Schweingruber1
1Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, CH-8903 Birmensdorf, Switzerland.
Fast-growing Eucalyptus trees exhibit unique stem radius changes, with xylem fluctuations driving total changes, unlike slow-growing species. This suggests the xylem, not bark, is the primary water storage tissue in these trees.
Area of Science:
- Plant physiology
- Forest science
- Ecology
Background:
- Tree water relations are typically interpreted using data from slow-growing species.
- The ratio of xylem to bark radial changes (DRXylem/DRBark) is usually low (<0.4), indicating bark's role in water storage.
- Understanding stem hydraulics is crucial for tree water relations.
Purpose of the Study:
- To investigate tree water relations in fast-growing Eucalyptus globulus using point dendrometers.
- To determine the drivers of stem radius changes (DRTotal) in Eucalyptus.
- To compare Eucalyptus stem hydraulics with established models based on slow-growing species.
Main Methods:
- Field study using point dendrometers on Eucalyptus globulus in Tasmania.
- Measurement of diurnal stem radius fluctuations (DRTotal).
- Analysis of xylem (DRXylem) and bark (DRBark) contributions to DRTotal.
- Hydraulic plant modeling to simulate and explain observed responses.
Main Results:
- Eucalyptus xylem fluctuations (DRXylem) were the main driver of total stem radius changes (DRTotal).
- The DRXylem/DRBark ratio was significantly higher (0.6-1.6) than previously reported for other species.
- Simulations indicated high tissue-specific elasticity of Eucalyptus xylem explains this atypical response.
- The wide zone of secondary thickening xylem contributes to wood elasticity and water storage.
Conclusions:
- Eucalyptus xylem acts as a significant water storage tissue, challenging previous interpretations.
- The high elasticity of Eucalyptus xylem influences water transport efficiency.
- Fast-growing species may have distinct hydraulic strategies compared to slow-growing trees.
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