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OZFACE
 
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OZFACE

OzFACE Experiment

To examine the impacts of carbon dioxide and climate change on tropical savannas, an experimental facility (OZFACE) has been established to:

  • determine the impacts of elevated carbon dioxide and altered climate on tropical savanna ecosystems and the enterprises they support;
  • quantify the potential for vegetation management practices to offset greenhouse gas emissions;
  • incorporate data into improved assessments of the impacts of climate change to support management and policy decisions.

The study will provide a better understanding of the impact that climate change will have on savanna ecosystems. This will allow the industry and government to develop adaptation strategies and policies.

At the core of the study is a Free-Air Carbon dioxide Enrichment (FACE) experiment located in a coastal tropical savanna at Queensland Nickel Pty Ltd's Yabulu refinery site, north-west of Townsville.

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Trends in Climate Change

Human activities have significantly altered the atmosphere over the last 200 years. The increase in 'greenhouse' gas concentrations has already led to a warming of the earth (around 0.6°C since 1900) and, as greenhouse gas concentrations are continuing to increase, the trend of warming will continue (Houghton JT, Meira Filho LG, Callander BA, Harris N, Kattenberg A & Maskell K (eds.) 1996 Climate Change 1995: The Science of Climate Change, University Press, Cambridge).

Almost half of these emissions are buffered by uptake in the oceans and assimilation into land-based ecosystems. But the excess emissions accumulate in the atmosphere contributing to global warming and climate change. Based on current trends, the earth will warm by 1.4 - 5.8°C this century and there will be substantial shifts in weather patterns.

Tropical savanna ecosystems will likely be strongly affected by these changes. There is some understanding of what the likely impacts will be at the scale of individual plants (e.g., effects on plant physiology), but we don't yet know how complex ecosystems, with their many interacting components, will respond. There are likely to be changes in nutrient cycling, soil carbon storage, grass production and its nutritive value as forage, the proportion of woody vs grassy vegetation, and catchment hydrology.

These will have important implications for the pastoral industry (the predominant user of savannas), carbon sequestration (and potential trading of carbon credits) and other aspects of natural resource management (e.g., management of catchments draining into the Great Barrier Reef lagoon).

Such changes will produce both opportunities and challenges for adapting existing land use practices to the altered environments of the future.

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The FACE Facility

To address these issues, a FACE facility was proposed and constructed in 2001 with the aid of an Australian Research Council grant. This system allows us to study the effects of increased carbon dioxide on an unenclosed, intact ecosystem with a minimum of disturbance.

One of the FACE experiment vegetation rings

FACE systems are expensive to operate (particularly in their usage of carbon dioxide) but capture the natural complexity of soils, vegetation, microbes, insects and carbon and nutrient cycles that could not be replicated in glasshouse studies. The operation of the OzFACE facility would not be possible without the support of Queensland Nickel Pty Ltd (QNPL), who provides the carbon dioxide and electricity together with the infrastructure to supply these to the site.

The OZFACE facility is operated jointly by CSIRO, Queensland Nickel and James Cook University with additional funding support provided by the Australian Greenhouse Office, the Australian Research Council and the Tropical Savannas Management Cooperative Research Centre. It has generated collaboration with researchers from other institutions (e.g., University of Melbourne, Bristol University) and is the first of its kind in Australia, the first in any tropical ecosystem, and the first to use an industry.

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The FACE Design

The FACE system consists of six rings, each 15 m in diameter. The vegetation enclosed by two rings is exposed to ambient CO2 (370ppm), two rings are exposed to a CO2 level of 460 ppm and the remaining two rings are exposed to CO2 concentrations of 550ppm.

Vegetation ring being exposed to CO2

Within these plot areas, one third of the area is left intact, one third is clipped to simulate grazing and one third has nutrients added to simulate higher fertility savanna locations. Local eucalypt and acacia seedlings have been planted to study woody-grass dynamics. This is a critical issue in savannas, in terms of current land management practices and the impacts of future climate. Plant and soil carbon is being measured to examine the interaction between rising CO2 and the ability of these systems to store carbon.

Scientist Andrew Ash examines an acacia seedling within a FACE vegetation ring

Target CO2 concentrations are achieved by controlling the amount and location of release of CO2 from different parts of the ring according to the direction and velocity of the wind. Carbon dioxide usage is approximately 1.5 tonnes per day. The experiment is planned to run a minimum of five years - this time frame is necessary to detect changes in plant species composition and carbon dynamics.

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Preliminary Findings

A range of measurements of ecosystem parameters and responses are being made at the site. These include vegetation composition, net primary productivity, forage quality and plant nutrient pools, soil moisture, soil carbon and nutrients, soil microbial activity, litter decomposition and various aspects of plant physiology. Baseline measurements were made at the time of the facility's construction and these have been followed up with regular monitoring since.

One ecosystem response that has been rapid is the response of grass production, with vegetation in the 550 ppm rings (985 kg/ha) showing an 103% increase in above ground net primary production relative to ambient controls (484 kg/ha) in the first full growth season (2001/02) of the study. But this might have been a short-term enhancement of growth and water use efficiency in response to the initial application of the CO2 treatments. In the past growth season (2002/03), which was very dry, we did not observe any enhanced grass production.

An important aspect of the study will be to test for longer-term vegetation responses to CO2 (including possible negative effects) and to examine the interaction of elevated CO2 with natural variation in rainfall. We predict that elevated CO2 may reduce the effects of drought periods / rainfall variability on vegetation.

Most other ecosystem properties that are being measured would be expected to take longer to respond. Our intention is to continue monitoring changes over the next 3-5 years to determine these longer-term responses.

We will use information gathered from the FACE study to predict the likely implications of climate change for the vast tracts of savanna across northern Australia. This will serve to inform policy and management decisions dealing with climate change.

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More Information

Publications

pdf icon Climate Change and Australia's Tropical Savannas
(pdf file 563 Kb)
pdf icon Carbon in Australia's tropical savannas (CSIRO media release)
pdf icon Rising CO2: what's in store for the savannas?
pdf icon Breath-testing the savannas (article in ECOS)
pdf icon Breath-testing the grasslands (CSIRO Media release)
pdf icon OzFACE (International Rangelands Congress 2003)
(pdf file 244 Kb)

Links

Bullet CSE Rangelands and Savannas
Bullet Tropical Savannas CRC
Bullet James Cook University
Bullet Australian Greenhouse Office
Bullet CSIRO Atmospheric Research

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Contacts

Dr Chris Stokes

Project Leader
(CSE Townsville)
Chris.Stokes@csiro.au

Dr Andrew Ash

Rangelands and Savannas Program Leader
(CSE Brisbane)
Andrew.Ash@csiro.au

Mr Mike Whiting

(CSE Townsville)
Mike.Whiting@csiro.au

Joe Holtum

(James Cook University)
Joseph.Holtum@jcu.edu.au



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