think climate. think change.
Department of Climate Change
Australian Greenhouse Office, Department of the Environment and Water Resources, 2007
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Future atmospheric and associated climatic changes are likely to have marked effects on Australian forest ecology impacting both wood production and the environmental services derived from forests. Increasing concentrations of CO2 in the atmosphere have the potential to significantly affect forest growth rates, the amount of carbon stored in forest ecosystems, forest biodiversity and the quantity and quality of water derived from forested catchments. Increasing CO2 concentration interacts in complicated ways with climate, land use and land management, and major disturbances such as bushfire to determine landscape and national impacts. Improved understanding of how elevated CO2 affects wooded land systems and surface-atmosphere interactions, will also improve climate models and potentially the reliability of regional climate predictions.
This report examines a broad range of issues that would underpin a decision to establish forest FACE (Free Air CO2 Enrichment) research facilities in Australia. In preparing this report, the authors invited and considered inputs from a wide range of scientific experts, representatives of the forest production and conservation sectors, and the leaders of forest FACE studies in North America and Europe.
Forest FACE studies, coupled with process-based models are the best approach to gaining evidence-based insights into the long-term effects of elevated CO2 on forest ecosystem processes and properties. FACE enables study of stand-level processes over extended periods, especially feedbacks that affect soil nutrient and water availability and plant competition, and thus the long-term effects of elevated CO2. Long-term FACE studies also enable the interactions between climatic variability or change, elevated CO2 and stand functioning to be explored.
There is a strong justification for establishing forest FACE studies in Australia, to build upon laboratory and whole-tree chamber studies on native species, and to complement on-going FACE experiments in temperate plantation forests growing on more fertile sites in the northern hemisphere. Australian forests have mostly evolved under water and nutrient limited conditions and regular disturbance, especially from fire. Thus Australian forest environments differ from those where existing FACE studies are being undertaken, and our sclerophyllous (hard leaved) vegetation may exhibit differing responses to elevated CO2.
For practical reasons, forest FACE experiments would be restricted to very few locations and experimental manipulations. It is clearly not possible to study the range of Australian forest ecosystems. Any selected site is not necessarily a good sample of even the broader range of that forest type, let alone the Australian forest estate. However, sites that have the broadly common characteristics (e.g. water and nutrient limitation) of a large portion of the forest estate can be studied. A viable approach is to use a comprehensive forest FACE study to test and improve existing process-based models that integrate the key processes describing the effects of elevated CO2 on forest carbon, water and nutrient cycles. The modelling framework is used to define the key gaps in current understanding, and research at the FACE site is then undertaken to address these gaps. The refined model becomes the tool for analyzing the potential effects of elevated CO2 on the broader Australian forest estate.
Native eucalypt forests, plantations and rainforests are very different ecosystems, with contrasting importance assigned to various forest values (e.g. wood production, biodiversity, water yield). Thus the significance of any impacts of elevated CO2 differs markedly in these forest types. Whilst there are valid reasons for conducting FACE studies in each of these forest systems, we recommend that an initial forest FACE study be established in either open dry sclerophyll forest or woodland that typically has a N-fixing woody understorey. Such forests dominate (>80%) Australian forested landscapes. Given the widespread and recurrent disturbance by fire of dry eucalypt forests, we recommend that fire be explored as a key variable in the FACE study.
However, we recognise that the providers of primary funding for a forest FACE study might have specific objectives (e.g. timber production, biodiversity conservation, water production) that could influence the preferred choice of site. Options for establishing a FACE study in a plantation or a rainforest should be further explored at a later time with appropriate stakeholders. We emphasise that FACE studies are easiest to conduct in young plantations, and logistically very difficult in tall, multi-species and heterogeneous rainforest.
There is now more than a decade of experience with forest FACE studies overseas that can be drawn upon to guide the establishment of a successful facility and associated research program in Australia. Of the techniques available, we recommend the use of a pure CO2 injection method that requires less infrastructure and introduces less potential artefacts. Critical issues relating to the practical design and application of FACE technologies, such as the minimum size of FACE ‘rings’, control of CO2 concentration within the stand, temporal increase in global CO2 levels, and variable carbon dioxide quality, are discussed in detail in the report.
The costs of establishing and maintaining forest FACE depends largely on the size and number of ‘rings’ established and the “deal” that can be established for discounted CO2 gas supply. The infrastructure costs may be ~ $50-100 k per ring (30 m diameter) but depend on many factors. These are small in comparison to the annual cost of CO2 (~ $0.4M to $1M per 30 m ring for a forest of 20 m height, based on discount commercial rates for CO2), and technical support (~$350k pa). Indicative total annual running costs for a forest FACE employing 4 ‘rings’ in 20 m high forest are approximately $2M to $4.5M. Commitment to running the FACE study for a decade or longer is required to enable long-term feedbacks to important forest processes to be expressed and understood. Given the high costs of CO2, partnering with industry to ‘sponsor’ some of this cost should be vigorously explored.
The high cost of establishing and maintaining a forest FACE facility, demands an efficient experimental design, and an integrated program of explanatory research that leads to interpretable findings and systematic refinement of models. The site must be readily accessible and attractive to a critical mass of multi-disciplinary scientists and students.
An Australian forest FACE facility would represent a long-term investment of national and international importance, and thus needs to be carefully designed and managed. A strong alignment between scientists, the full spectrum of relevant funding bodies and experimental infrastructure is needed. To facilitate this, we strongly recommend that a broadly-based Steering Committee that represents the key groups (governments, private sector interested in carbon, water and biodiversity, R&D corporations, research providers, and active researchers) investing in the facility and in the associated research be established. A Scientific Committee with adequate multi-disciplinary expertise (including elevated CO2 research) is also needed to co-ordinate research at the site, ensure that key observations are undertaken and made readily available, and work closely with the Steering Committee. A strong collaborative model involving all participants is essential.
