University of Tasmania, Australia

By clearing vegetation and burning fossil fuels human beings are drastically increasing the concentration of carbon dioxide (CO₂) in the atmosphere. CO₂ is the main greenhouse gas and is associated with the shift in the greenhouse effect that is leading to global warming. While global warming is enough to worry about in its own right, the CO₂ itself has a direct impact on plants and therefore on ecosystems, since plants use CO₂ as the raw material out of which they construct sugars, proteins, oils, leaves, wood, flowers, fruit and all ultimately all food on the surface of the planet. Plants are very sensitive to changes in the concentration of CO₂ in the atmosphere, and therefore all other living things are also affected by changes in the concentration of CO₂

The concentration of CO₂ is increasing rapidly (see figure above). So is the global temperature (see figure below). The impacts of these two factors are likely to be immense for both natural and managed ecosystems. The TasFACE experiment is one of only a handful in the world that is examining the impact of both increasing CO₂ concentration and global warming on an intact ecosystem

Grasslands of southeastern Australia are of immense importance both in conservation terms and as an agricultural resource. Since European settlement, 99% of Australia’s natural temperate grasslands have been destroyed or significantly modified, making them perhaps the vegetation type most altered in southeastern Australia. However, modified grassland or “native pasture” still occupies large areas in southeastern Australia. In Tasmania, for instance, “native pasture” accounts for approximately 40% of the 1.3 million hectares of grazed lands. Furthermore, these grasslands contain a large number of threatened genotypes, species and communities, making the successful management of grassy vegetation a crucial aspect of maintaining biodiversity. Grassy vegetation also has great economic importance, since these vegetation types are used extensively for cattle and sheep production. It has been shown that the health of native pasture is declining, which is a matter of concern to both the grazing industry and the conservation community.

The major problems identified for the southeastern Australian grasslands include:

• Poor persistence of species, particularly native perennial species
• The proliferation of weeds
• The disappearance of species with low nutrient requirements
• The poor persistence of sown species
• Decline in pasture production and vigour

So far, work on the management of native pastures in southeastern Australia has not considered the impact of global climate change. However, the very factors that are seen as the major problems in pasture decline, namely loss of native perennial grasses and the proliferation of weeds, are highly likely to be exacerbated by global climate change. The increase in atmospheric CO₂ is a particularly important determinant of the changes to species composition, as evidenced in much research from other parts of the world.

This project aims to investigate the likely impacts of global climate change on southeastern Australian native pasture by determining the effects of elevated CO₂ and temperature on the physiology, growth, reproduction and recruitment of pasture species, as well as on species composition, overall pasture productivity and nutritional quality. It also aims to investigate the individual and interactive effects of increases in temperature and increases in CO₂, thereby increasing our ability to predict pasture responses to different climatic scenarios.

The TasFACE experiment is located within the Australian Federal Department of Defence Pontville Small Arms Range Complex (PSARC) at Pontville, SE Tasmania at 42° 42’ S 147° 16’ E (map). The site is approximately 30 km north of Hobart and is located on a basalt plain at an altitude of 40 m a.s.l. Soil at the site is black basaltic clay and is best classified as a black vertosol. Climate is Mediterranean with a mean annual temperature of 11.6°C and mean annual rainfall of 560 mm, although the site has experienced severe drought since the experiment commenced. The site has a mean windspeed of 2.7 m s -1 at 2 m above ground height.

The TasFACE experiment is established in a flat, reasonably uniform area of lowland Themeda-Austrodanthonia grassland (photo). The entire study site is 30 ´ 30 m and contains approximately 60 species, but the grasses Themeda triandra, Austrodanthonia setaceae and Austrodanthonia caespitosa dominate.

TasFACE commenced operation in February 2002. The current round of funding covers the period until December 2006.

The TasFACE experiment is a two factor experiment in which vegetation within 1.5 m rings is exposed to either elevated or ambient [CO₂] and either ambient temperature or +2 ° C warming. Experimental treatments are replicated three times. There are six ambient and six FACE treated rings, half of which are treated with IR lamps. Thus, there are three rings designated controls and three each of FACE alone, IR alone and FACE+IR in combination (see photo of rings and lamps). [CO₂] within the FACE treatment rings is set to 550 µmol mol -1.

The design and control of the FACE treatment are a modification of the POPFACE pure-CO₂ injection design. The 1.5 m diameter rings are made of 4.5 m long 20 mm internal diameter PVC pipes with 0.3 mm laser-drilled holes every 50 mm along the outside edge (see photo of a ring).

[CO₂] is controlled using a dedicated programmable microprocessor-based control system. Gas is sampled from the centre of each FACE ring using a high velocity air pump and monitored by one of two infrared gas analysers (IRGAs). Pure CO₂ is supplied from a 6 t bulk store and CO₂ release in each ring is controlled by electropneumatic flow-control valves, dependent upon [CO₂] as measured by the IRGA and wind velocity as estimated by a cup anemometer. Fumigation commences at sunrise and ceases at sunset each day. Valves are not closed at high wind velocities, as occurs in some other FACE experiments (see photo of control system)

Warming is provided by a single 240 V 250 W Solid Ceramic Infrared Emitter suspended 1.2 m above the soil surface above the centre of each ring. The IR emitters operate continuously.

Climate change experiments are classified as having good control if the [CO₂] is within 20% of the set-point for 80% of the time. The temporal [CO₂] control of the TasFACE experiment far exceeds this criterion since the central [CO₂] is within 20% of the set-point for 97% of the time. Indeed, all FACE rings are within 10% of the set-point more than 85% of the time.

The infrared heaters produce an average elevation in abaxial leaf temperature of 1.98°C, in adaxial leaf temperature of 2.20°C and of shielded air temperature at canopy level of 2.16°C during the growing season. Soil temperature at 1 cm depth is elevated by an average of 0.82°C. Warming varies over the day and is greater during the night. The elevation of air temperature is accompanied by an average decline in relative humidity of 5.1%, which is most pronounced during the night.

TasFACE is established in a high quality lowland grassland on a basalt plain. The study site contains approximately 60 vascular plant species. We are making measurements from all scales from the ecophysiology and anatomy of individual plants, through plant population dynamics and community interactions to ecosystem processes. Our main ecological aim is to achieve an understanding of the processes whereby elevated CO₂ and global warming impact upon natural ecosystems.

While we aim to maximise the amount of information we obtain from the TasFACE experiment, we cannot do so alone. We would welcome requests for collaboration, particularly from people interested in plant-animal interactions, fungal biology, microbiology and soil processes. Contact Mark Hovenden (Mark.Hovenden@utas.edu.au) with any proposals.

Dr Mark Hovenden: Mark is the chief investigator and was responsible for the establishment of the TasFACE experiment. He is also responsible for all repairs, so if it isn't working it is entirely his fault. Mark is also in charge of all ecophysiological measurements and the integration of the efforts of staff.

Dr Karen Wills: Karen is in charge of the population and community level investigations and also does a lot of other ecological bits and pieces. 

Jackie VanderSchoor: Jackie is the backbone of the TasFACE project and is responsible for day to day running and maintenance as well as for working closely with Karen on the community and population level measurements. At the moment Jackie is spending a lot of time monitoring seedling fate.

Dr Paul Newton: Paul is the director of the Grazed FACE experiment in New Zealand and is the main partner investigator on the TasFACE experiment. Paul provides advice on pasture population dynamics and pasture quality assessment. Paul also provides advice on all aspects of climate change science.

Dr Franco Miglietta: TasFACE was established through a collaboration between the University of Tasmania and Dr Franco Miglietta of Ibimet, the Italian Institute for Biometeorology in Florence. Dr Miglietta and Alessandro Zaldei designed the TasFACE CO₂ control system. TasFACE would not exist without their generous assistance and ingenuity in design. 

Past involvement

Jasmine Janes: Jasmine spent a year getting to grips with seedling fate in the grassland and discovered startling results. Jasmine took many of the outstanding photos on this web site (Mark took the poor ones). Jasmine is now working on population dynamics of orchids, her true love.

Becky Chaplain: Becky spent two summers measuring flowering and seed production in TasFACE. Becky is now at Princeton University (a little place in the USA).