HR: 1340h
AN: B23C-1498    [Abstracts]
TI: Where Does The Carbon Go? Carbon Dynamics And Fire of a North Australian Tropical Savanna
AU: * Hutley, L B
EM: lindsay.hutley@cdu.edu.au
AF: School of Science and Primary Industries, Charles Darwin University, Darwin, NT 0909, Australia
AU: Beringer, J
EM: jason.beringer@arts.monash.edu.au
AF: School of Geography and Environmental Science, Monash University, Melbourne, Vic 3800, Australia
AU: Tapper, N J
EM: nigel.tapper@arts.monash.edu.au
AF: School of Geography and Environmental Science, Monash University, Melbourne, Vic 3800, Australia
AU: Cernusak, L
EM: CernusakL@si.edu
AF: School of Science and Primary Industries, Charles Darwin University, Darwin, NT 0909, Australia
AB: The role of fire as one of the primary natural carbon cycling mechanisms is a key issue in considering global change feedbacks. In north Australia, the dominant ecosystem is tropical savanna and for mesic savannas within 100 km of the northern coastline, fire, storms and cyclones all impact carbon stocks. Fire is the most frequent disturbance agent as fires burn with a near annual frequency in these systems. We aimed to determine the annual net ecosystem productivity (NEP) from these savannas and the impact of fire on productivity. We established a long-term eddy covariance flux tower at Howard Springs, Australia and present here 5 years of data from 2001 to 2005. Fire has direct impacts through emissions but also has indirect effects through the loss of productivity due to reduced functional leaf area index and the carbon costs of rebuilding the canopy. The impact of fire on the canopy latent energy exchange was evident for 40 days while the canopy was rebuilt; however, the carbon balance took approximately 70 days to recover. The annual fire free NEP at Howard Springs was estimated at -4.3 t C ha-1 y-1 with a range of -3.5 to -5.1 t C ha-1 y-1 across years. We calculated the average annual indirect fire effect as 0.7 t C ha-1 y-1 using a neural network model approach and estimated average emissions of fine and coarse fuels as 1.6 t C ha-1 y-1. This allowed us to calculate a net biome production of 2.0 t C ha-1 y-1. We then partitioned this remaining sink and suggest that most of this can be accounted for by woody increment (1.2 t C ha-1 y-1) and shrub encroachment (0.5 t C ha-1 y-1). Given the consistent sink at this site, even under an almost annual fire regime, there may be management options to increase carbon sequestration by reducing fire frequency.
UR: http://www.arts.monash.edu.au/ges/research/climate/fire/index.php
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0428 Carbon cycling (4806)
DE: 0476 Plant ecology (1851)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting