Radial growth dynamics of mature Eucalyptus tereticornis trees in Australia over a 10-year period: impacts of climatic factors and soil water availability

Details

Supervisors

Vincke, Caroline ; Ellsworth, David

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

Eucalyptus forests are essential ecosystems for Australia. Representing 80% of Australia’s native forests, they provide ecosystem services, including carbon sequestration, and bring a massive biodiversity among their 800 species. In the last decade, Australia has been hit by extreme climatic events (droughts, fires, floods). Although certain drought adaptations are known for Eucalyptus trees, such as osmotic regulation and changes to the root system, little is known about how these trees react to long-term environmental stresses, particularly in terms of radial growth. This master thesis aims to understand changes in radial growth of Eucalyptus tereticornis in relation to climate factors and soil moisture over a ten-year period. This work was focused on two objectives: (1) identifying the preferred growing season of E. tereticornis trees and (2) determining which soil zone correlates best to long-term radial growth. For this, radial growth was measured with band dendrometers in the Eucalyptus Free Air CO2 Enrichment Facility (EucFACE), Western Sydney University, Richmond, NSW, Australia. Radial growth data have been collected every month since 2012, while soil moisture was monitored at different depths using TDR and neutron probes, and its relationship with growth was assessed using climatic and edaphic drought indicators. After running statistical analyses, its was showed that dominant trees grew more in autumn, with significant differences compared to other seasons. Codominant trees, however, showed more variable seasonal growth, peaking in either autumn or spring. Results indicated that dominant trees had greater annual growth than codominant trees, and their radial growth was more sensitive to climatic drought. Additionally, we found that growth was strongly correlated with soil moisture in the upper layers (30-75 cm), particularly under dry conditions, suggesting that these layers are critical for water supply during growth periods. This work concluded that both seasonal growth patterns and soil moisture dynamics are important to improve the knowledge of E. tereticornis’s adaptation to drought.