Recently we sent Mr Dave Boadle down to the University of Western Sydney (Hawkesbury Campus) to assist with the installation of their new eddy covariance station. While the installation went off smoothly, a brief tour showed the extent of their use of our equipment. The Whole Tree Chambers and Rain Out Shelters use our CS616 and CR1000 loggers, while their greenhouses even have a trace gas analyser(TGA). With the eddy covariance system now added to their inventory they really are valued customers of Campbell Scientific Australia. Following is a case study of some of the valuable and exciting projects happening at this campus.
The Hawkesbury Forest Experiment - University of Western Sydney
In 2009, the University of Western Sydney received $40 million from the Australian government’s Education Investment Fund (EIF) to establish a national facility for climate change and energy research (CCER) on the Hawkesbury Campus in Richmond, NSW. This new facility will house one of Australia’s most comprehensive climate change programs by providing scientific infrastructure to conduct cell-to-ecosystem research, thereby generating information about the impact of climate change on biological function at numerous levels.
Whole-Tree Chambers
In 2006, UWS received 12 whole-tree chambers (WTCs) from Sweden (courtesy of Prof Sune Linder, Swedish University of Agricultural Sciences) for use at the Hawkesbury Forest Experiment (HFE). In 2007, a 2-year experiment was initiated to study the impact of elevated CO2 and summer drought on fast-growing Eucalyptus saligna. The WTCs comprise a field-based experimental tree chamber system designed to grow single trees up to 9 m tall in elevated atmospheric CO2, with the capacity to control air temperature and soil moisture. The unique attribute of the field-based WTCs is the capacity to simultaneously measure whole-tree fluxes of CO2 and water vapour. Whole system gas exchange may be measured continuously once the tree reaches about 2 m height. At that time, a plastic partition is installed around the tree stem that separates the above ground tree shoot from the below ground rhizosphere, thereby establishing separate measurements of carbon and water gas exchange for the two locations.
Investment from EIF has provided funding to improve the WTC system in the following ways:
(i) while controlling temperature very well to track ambient conditions (to within ± 0.5 oC across the range from 0-40oC, the ability to simulate climate warming during day and night was added by including 6kW heaters in each chamber;
(ii) cooling capacity of the chambers was improved to help reject heat under harsh conditions in summer (e.g., > 40oC); and
(iii) there is independent control of temperature and relative humidity (RH) so that vapour pressure deficit (D) may be controlled within each WTC; RH and D control is crucial in warming experiments to avoid confounding temperature and D effects on plant processes. In its current configuration, the WTCs are used to investigate the responses of plantation Eucalyptus trees to atmospheric CO2 for current CO2 +240ppm and +3oC warming to understand how reforestation and tree plantation efforts can cope with plantation forests under future climate change scenarios. Rising atmospheric CO2 has important ecological implications because the CO2 fertilisation effect has the potential to increase carbon assimilation and reduce water loss on a leaf- and whole-tree basis, thereby increasing water use efficiency. Alterations in the carbon and water balance in whole trees, and associated changes in nutrient cycling, microbial function and plant/insect interactions, may have profound effects on carbon and water cycles across forested landscapes.
Subsequently, this facility represents an opportunity to increase the scale of field-based elevated CO2 experiments in Australia using woody species, which previously encompassed trees reaching only a few metres tall.
Rain-Out Shelters
UWS built six large, rain-sensing, automatic retractable roof rainout shelters (12m long x 8m wide x 7m tall) in the field; associated with each shelter is a control plot of equal size. Control and rainout shelter plots are exposed to the same natural environmental conditions except when rain events are excluded from the rainout shelter plots. The shelters are constructed of welded aluminium with mounted moisture (rain) sensors that can be set to different rainfall event size sensitivities. When rain is detected, transparent plastic curtains are automatically deployed and unrolled from the top of the peaked roof of the shelter; concertina curtains of the same material are expanded in three sections on each side of the shelter. A 1 m gap at the bottom of the rainout shelter is designed to maintain air flow from the outside environment into the shelter to minimize the impact of the curtain on the site microclimate. After the rainfall exclusion event, the curtains will be raised to their original fully retracted (i.e. rolled) position.
Rainwater will be collected on-site using a roof collection system, stored in a 220,000 L water reservoir and available for re-application to the shelter trees at the appropriate time. Partitions have been inserted into the soil (at the drip line of each shelter) to a depth of 1m to exclude lateral water flow from unsheltered locations. Tree seedlings will be planted into sheltered and unsheltered plots at equal planting densities and border trees will be planted to reduce wind-blown rainfall from reaching the experimental trees within each shelter. All plots have been extensively equipped with environmental sensors linked to data loggers to measure wind speed, relative humidity, air temperature, light, soil temperature, soil moisture, and soil water potential at different depths and locations. Environmental conditions will be continuously monitored throughout the duration of the experiment. Using this facility, UWS will conduct the first field-based precipitation manipulation experiment on trees in Australia in which we have the capacity to maintain natural variability in the amount of annual precipitation, but alter the timing and magnitude of seasonal precipitation (i.e. summer or winter) using rainout shelters to redistribute rainfall seasonally. In addition, they will use rain-out shelters to impose long drought periods on tree seedlings & saplings to assess the proximate physiological cause of mortality through hydraulic failure and/or carbon starvation.
Eddy Flux
In the Cumberland Plain woodland, UWS will establish an eddy covariance (flux) site to measure the exchange of CO2 and water between the woodland vegetation and the atmosphere under natural environmental conditions. The vegetation at the site is dominated by Eucalyptus trees (ca. 20-25m tall) and an understorey comprising a wide range of species, but dominated by Bursaria, Melaleuca and C3 and C4 grasses. A 30m tower will be airlifted into the site, to avoid disturbance of the native vegetation, and then fitted with standard eddy covariance gear. They will measure canopy energy balance, as well as the turbulent fluxes of momentum, heat, water vapour and CO2, which will require measurement of net radiation flux, soil heat flux, and heat storage in the soil and canopy. Protocols for flux measurements, data storage and processing will follow guidelines developed by the national Terrestrial Ecosystem Research Network (TERN) and OzFlux. Flux measurements will be complemented by standard plant growth, sap flux, soil respiration, and leaflevel gas exchange measurements to provide insight into the individual processes controlling ecosystem exchange of carbon and water.
Conclusions
We are very fortunate that the Australian government and the University of Western Sydney have contributed significant financial resources to build this cell-to-ecosystem climate change facility. When it is completed, it will represent one of the largest facilities developed for climate change research in the Southern Hemisphere. They hope that scientists in Australia and around the world will join them in our research efforts to address one of the most significant issues of the Anthropocene era.
Case Study Courtesy of Professor David Tissue
Theme Leader Climate Change -Centre for Plants and the Environment University of Western Sydney
Photos Courtesy of Markus Riegler
For more Information about Eddy Flux Systems contact our office on +61 (0)7 4401 7700