Hawkesbury Institute for the Environment

Expansion of the Hawkesbury Forest Experiment (HFE)

The Institute received a grant from the Department of Agriculture, Fisheries and Forestry via the Forest Industries Climate Change Research Fund for the project ‘The Hawkesbury Forest Experiment: providing the missing information for decision support systems to manage forests under rising CO₂ and global warming’.

Project Brief

Australia’s forest industry must develop strategies to capitalise on opportunities and minimise risks arising from higher CO₂ concentrations and global warming. The proposed project will use the unique tree chamber facilities of the Hawkesbury Forest Experiment and a commercial plantation to generate critical new information that is currently unavailable about the interactive effects of elevated CO₂ and increasing temperatures on processes underpinning growth and water use of eucalypts. The data will then be used to develop and refine process-based models that can be used by the forestry industry for management of plantations under future climates.

Outcomes from the Project

• Generation of critical new information about the interactive effect of high temperatures and rising CO₂ on whole tree carbon and water flux of plantation-eucalypt species. This was recognised as a key unknown in a recent analysis of the vulnerability to climate change of Australia’s forest plantations.
• Use the new experimental data generated from our field experiments to refine processbased models that can be used by forest managers and integrated into decision support systems to enable the forestry industry to take advantage of opportunities and reduce risks arising from climate change.
• Ensure that the results of the project are communicated to the target groups of the project including key members of the forestry industry in Australia.

Project description

The proposed project will assess the impacts of higher temperatures and elevated CO₂ on the trade-off between forest growth and water use in a Eucalyptus plantation. We will focus on tree canopy carbon capture and water use, both of which are rarely measured in the field. The project will take advantage of a substantial upgrade of the Hawkesbury Forest Experiment (HFE) – the only field-based CO₂ enrichment experiment on trees in Australia – which utilises twelve, whole-tree chambers that house trees up to 10 m tall and can accurately measure whole tree CO₂ uptake and water loss. The HFE upgrade, which was funded as part of a grant package for climate change and energy infrastructure at UWS through the Education Investment Fund (EIF), provides the ability to control both air temperature and vapour pressure deficit (VPD). This is a tremendous technological advance that avoids the complications of most warming experiments, which confound temperature and VPD effects on evapo-transpiration, thereby making data interpretation much more complex.

Currently, there is no Australian field experiment evaluating the potential interactions between CO₂ enrichment and warming on trees; importantly, this is also an international research priority for forest growth studies (Ledford 2009, Nature). In addition to our chamber experiment, a parallel plantation will be established by our forest industry partner (Forest Enterprises Australia Ltd. Group of Companies, a forest industry Managed Investment Scheme) on a managed plantation site near Casino in northern NSW. The two sites differ in average temperature by 2.7^oC, which is approximately the target climate offset (+ 3^oC) of the whole-tree chambers in Richmond, NSW. This will provide a first-ever evaluation of tree adaptation to climate by both experimental manipulation at one site, as well as latitudinal plantings between sites. These experiments will generate much needed data about adaptation of eucalypts to different temperature environments – knowledge that is crucial for expanding plantations of eucalypts with desirable characteristics from one temperature zone to another.

Insect predation of leaves is also a critical issue for eucalypt plantations which lose three times more carbon through insect feeding than any northern hemisphere tree species. We know that elevated CO₂ alters the nutritional composition of leaves and is likely to alter insect feeding, but little is known about the interactive effects of elevated CO₂ and warming. In addition, this experiment allows us to assess insect genetic variability and adaptation of insect pest populations to these climate variables, which to date has not been explored.

It is important to ensure that the information generated by the project can be readily adopted by industry. To achieve this outcome, we have a carefully designed modelling strategy in place utilising process-based models that operate at different scales. This project will use a detailed ecophysiological model of tree carbon uptake and water use as a framework for integrating and analysing experimental outcomes. This model will then be used to generate response surfaces for CO₂ and warming impacts that can be incorporated into forest stand scale models and decision support systems.