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The Monitor - Issue 5 - Getting to grips with the competition

Eucalypt plantation where paired-plot trials are being established

Plant competition may be particularly important in the first few years of forest growth. Tony O’Grady, in combination with industry partners in Tasmania and the Green Triangle, has been establishing a series of trials consisting of paired growth plots with and without competition in eucalypt and pine plantations to better understand the effects of competition on forest health.

These paired-plots trials will provide the opportunity to measure and monitor impacts of weed competition on the early growth of plantation species, and to develop a valuable database of growth with and without competing vegetation that can be used to test and validate models.

To understand the mechanisms of competition we need to better understand the spatial and temporal patterns of overstorey and understorey leaf area index (LAI).  Maria Ottenschlaeger (CSIRO) has been measuring the seasonal and spatial patterns of leaf area index in Eucalyptus nitens chronosequence in the Florentine Valley in Tasmania. In many Tasmanian sites, woody vegetation contributes significantly to understorey LAI and Maria has put considerable effort into developing methods for quantifying LAI in common understorey woody species. This work is providing information for estimating changes in understorey leaf area and biomass with plant growth. Both leaf area and biomass are critical inputs for models predicting understorey water use and carbon sequestration.

Digital photograph used to assess canopy cover

Furthermore, optical methods (Li Cor LAI2000, digital photography) are being trialled to discriminate seasonal patterns in LAI. These provide important methodological background to our work, and also make a significant contribution to the water balance studies being led by Sandra Roberts (Forestry Tasmania) in Program Four.

A major focus of this research will be to understand, in detail, the mechanisms controlling the exchanges of carbon and water in competing vegetation. This will help us better predict not only the competition in these communities but also the role these communities play in the water and carbon balance of planted forests. The implications of this research extend beyond traditional plantation forestry and can significantly contribute to the debates around biodiversity and plantings for carbon sequestration.

Dr Tony O’Grady

Leader of Project 1.3
Tel: 03 6226 7963