Measuring GHG fluxes in converting a tropical savanna to a managed ecosystem

Measuring GHG fluxes in converting a tropical savanna to a managed ecosystem

Fri, 02/05/2014 - 10:00 to 11:00


About the Presenter

Mila Bristow is a post-doc at CDU’s Research Institute for the Environment and Livelihoods investigating the impact of land use change by measuring greenhouse gas (GHG) emissions, soil carbon and nitrogen, water resources and dry season environmental flows in tropical savannas. Mila has worked in forest ecosystem science in northern Australia for over 18 years. She has researched growing rainforest trees and optimum plantation designs for tropical plantation species in north Queensland. She did her PhD with Southern Cross University studying competition in polycultures and the functional consequences of diversity in plantations. Any time of night or day she enjoys hanging out of cherry-pickers or in soil pits to measure carbon and water capture, storage and flux in plantations and native forests. Mila is interested in increasing productivity in managed forests, reducing simplicity in forested landscapes and measuring the trade-offs between conservation and development at the landscape scale.


Venue

Charles Darwin University
Ellengowan Drive
Building Red 1.3.01
Casuarina NT 0810
Australia

Clearing and burning of tropical savanna leads to globally significant emissions of greenhouse gases (GHG) although how much, for how long, and what drives these processes remains unknown. Australia’s tropical savannas occupy over 25% of the continental land mass, they significantly influence the national greenhouse gas budget, and they are currently the focus of government interest in agricultural expansion in Australia.

In a unique experiment, we measured GHG exchange for almost two years from two savanna woodland sites in the Northern Territory, one that was cleared and a second that remained uncleared. The cleared site consisted of continuous CO2 exchange using eddy covariance flux towers before, during and after clearing, plus fire-derived emissions from the burning of cleared debris. This record combined flux dynamics driven by the highly seasonal climate as well as that determined by the land use change. The uncleared site was a control site to compare relative impacts on fluxes.

Also at the cleared site we partitioned soil emissions of methane (CH4) and nitrous oxide (N2O) using periodic measurement from static manual chambers, before during and after the clearing event. Plus we measured the vegetation biomass pre-clearing to quantify the loss of standing carbon, and we measured soil physical characteristics to measure the impacts of converting savanna to cultivated farmland.

In this talk I will explain why and how we measured these GHGs, what the results show and why this sort of experiment is critical to understanding the impacts of land use change in northern Australia.

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