Written by: Sarah E. Perkins, Malcon J. Hauser & Sarah R. Sutcliffe
Our journey along the North Australian Tropical Transect continues as we now find ourselves in the old mining town, now gateway to Litchfield National Park, Batchelor.
Figure 1. Magnetic Termite Mounds, Litchfield National Park
First stop, the Batchelor airstrip and an informative discussion about Gamba grass by Professor Lindsay Hutley. Gamba grass represents a major land management concern in the Northern Territory. The actual and potential impacts of Gamba grass paint a bleak picture for the future of high rainfall savannas in the North. A key takeaway point for the group was its effect on reorientating fire architecture of savanna landscapes from relatively low to high intensity fire regime. Specifically, increasing highly flammable fuel loads and pushing flame height into the canopy layer which can lead to increased mortality of native woody vegetation.
Figure 2. Students listening to Professor Hutley's every word on the impacts of Gamba Grass. Note the distinct lack of native grasses and mid-storey plant species.
A formidable competitor, due partly to efficient uptake and utilisation of nutrients (nitrogen), Gamba acts to suppress not only native ground cover in grasses and shrubs but also the recruitment of canopy species. Comparatively, Gamba affected areas have been shown to achieve 8-10 t/ha-1 in biomass production as opposed to 1-3 t/ha1 in unaffected areas. This has considerable implications for carbon budgets in savanna ecosystems as whilst under fire, represents a significant input to atmospheric gas emissions of CO2, methane and nitrous oxide.
However, if well managed, Gamba provides a valuable improvement to production in pastoral activities. So while there are programmes in place to manage Gamba and control of spread is legislated, effective control of this Weed of National Significance may require further efforts.
After the airport, we settled in to our new home for the next few days at the Parks and Wildlife Ranger station new visitor’s quarters. We spent the afternoon relaxing and studying in the shade, escaping the heat of the day.
Early starts keep us out of the hottest part of the day on Transect 5 and we were rewarded for our efforts with some leisure time, soaking our muscles in the crystal clear waters of Bulley Rockhole.
Figure 3. Students enjoying a well-deserved break at Litchfield's Buley Rock Hole
The afternoon highlight was a special visit from CDU Research Associate Rohan Fisher who introduced the group to an interactive fire and rate of spread modelling system. Mapping data was first vertically projected onto a 3D model of Nitmuluk National Park, then onto sand giving some the opportunity to get creative with landscape topography of Gunbalunya (Oenpelli).
Figure 4. Students track the progress of mock aerial incendiary ignitions across the Nitmuluk National Park escarpment
Figure 5. Students creating a 3D landscape model of Gunbalunya (Oenpelli) using sand and projected topographic map of the area
After the excitement of hypothetically laying waste to some of the most pristine escarpment country in the Territory (!), all settled in for another exceptional dish by our Delta Team and engaged in interesting discussions about Nepalese caste systems. Topping off another great day in the field, we took in the chaos of confused fruit bats as they tried to escape the local Territory Day fireworks display at Batchelor Sports Oval.
The combination of broken sleep due to the intermittent explosions of the previous night’s fireworks and eight days in the field was definitely telling at the breakie bar this morning. Thankfully, the dependable Huon Clark had the black bitumen goodness at the ready and tired eyes soon turned to beaming dishes of enthusiasm for the final field day, and Transect number six.
The groups’ final transect was located within the Litchfield Tropical Savanna Super Site, one of 11 Supersites across Australia world. Super sites in Australia are areas that have been supported by the Terrestrial Ecosystem Research Network (TERN) as representative sites of different ecosystems across the nation.
Figure 6. Professor Hutley giving students an overview of the Flux Tower Network at the Litchfield Supersite
Highly sensitive monitoring equipment provides data in real-time and is collected to describe and compare different ecosystems as part of a global initiative, looking to improve climate models. We gathered near the flux tower at the Litchfield site to discuss the fully automated system and the benefits the data can have for various land users. Measurements are taken to calculate productivity, water use and carbon exchange with the atmosphere. Also being monitored is fauna and flora biodiversity, contributing to a database which is accessed by ecologists worldwide. It was exciting for students to see the site and hardware that is contributing to global research and realising the potential reach of research done right here in the Northern Territory.
Inspired by global perspectives on climate change and ecosystem studies, we are now all looking forward to analysing the data we have collected over this trip and discovering the hidden secrets of the North Australian Tropical Transect.
Figure 7. Staff and students pose at the Litchfield’s savanna supersite.