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Fire in Australian Savannas

Australian savanna

Australian savanna

eMASTer Bradley Evans was part of an international collaboration that investigated how savanna fires in Australia are coupled to the global climate through the carbon cycle and fire regimes. In the study Beringer and co-workers, currently in press in Global Change Biology and available online, review the understanding of the impact fire has upon biophysical and biogeochemical properties in Australian savannas at multiple scales, from leaf level physiology to regional climate. They focus on biophysics and biogeochemistry rather than ecological drivers since these have already been documented in other articles.

Beringer and co-workers are presenting new indications that climate change likely alters the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide (CO2), and in turn alters fire regimes with further feedbacks to climate. They also explored and present different opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.

 

To read the entire article click here or search for:

J. Beringer, L. B. Hutley, D. Abramson, S. K. Arndt, P. Briggs, M. Bristow, J. G. Canadell, L. A. Cernusak, D. Eamus, B. J. Evans, B. Fest, K. Goergen, S. P. Grover, J. Hacker, V. Haverd, K. Kanniah, S. J. Livesley, A. Lynch, S. Maier, C. Moore, M. Raupach, J. Russell-Smith, S. Scheiter, N. J. Tapper, P. Uotila; 2014. Fire in Australian Savannas: from leaf to landscape. Global Change Biology, in press. DOI:10.1111/gcb.12686

 

 

 

 

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Extreme cyclone events

Tree isodamage map showing the spatial extent of damage across the impact area of TC Monica as determined from wind field analysis plus areal and on-ground tree damage surveys as described by Cook and Goyens (2008). Contour lines are tree damage polygons ranging from 1–5% tree damage to >85% in 5% increments, giving 17 damage categories of known area. Picture insets show post-cyclone vegetation from contrasting damage polygons 1–5% (top left), >85% (top right) and 40–45% (mid-right). Pictures from Cook.

Tree isodamage map showing the spatial extent of damage across the impact area of TC Monica as determined from wind field analysis plus areal and on-ground tree damage surveys as described by Cook and Goyens (2008). Contour lines are tree damage polygons ranging from 1–5% tree damage to >85% in 5% increments, giving 17 damage categories of known area. Picture insets show post-cyclone vegetation from contrasting damage polygons 1–5% (top left), >85% (top right) and 40–45% (mid-right). Pictures from Cook.

Through eMAST's engagement in a number of landmark carbon and water cycle projects it is supporting research in northern Australia. Only recently eMAST's Bradley Evans was part of a research initiative intending to improve the understanding of processes that govern carbon, water and energy exchange in tropical savanna's in North Australia by investigating "Impacts of an extreme cyclone event on landscape-scale savanna fire, productivity and greenhouse gas emissions". The choice of tropical savanna ecosystems of the coastal and sub-coastal North Australia was mainly based on their experience of a unique combination of climatic extremes, which drive the regional ecosystem dynamics. They are in a state of near constant disturbance from fire events (1 in 3 years), storms resulting in wind-throw (1 in 5–10 years) and mega-cyclones (1 in 500–1000 years). To manage these unique ecosystem worldwide in a sustainable manner it is crucial to understand tropical savannas as ecosystems maintained by disturbances such as fire and grazing, or stable systems that persist despite these disturbances. Using the moderate resolution imaging spectroradiometer (MODIS) GPP (MOD17A2) Huntley and co-workers suggest that fire and termite consumption had a larger impact on Net Biome Productivity than infrequent mega-cyclones. They also demonstrate the importance of understanding how climate variability and disturbance impacts savanna dynamics in the context of the increasing interest in using savanna landscapes for enhanced carbon sinks in emission offset schemes.

For more information see:

Hutley, L.B., Evans, B.J., Beringer, J., Cook, G.D., Maier, S.M. and Razon, E., 2013, Impacts of an extreme cyclone event on landscape-scale savanna fire, productivity and greenhouse gas emissions, Environmental Research Letters,  8 (4), 045023. Available here.

 

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Bioclimatic extremes and forest mortality

Study area of Evans and Lyons (2013)

Study area of Evans and Lyons (2013)

The article "Bioclimatic extremes drive forest mortality in southwest, Western Australia" published by Bradley Evans and Tom Lyons in 2013, Climate 1, 28-52, show that extreme and persistent reductions in annual precipitation and an increase in the mean diurnal temperature range have resulted in patch scale forest mortality following the summer of 2010–2011 within the Forest study area near Perth, Western Australia. The authors found that spatially aggregated seasonal climatologies across the study area are 2011, with an annual mean of 17.7°C (± 5.3°C), 1.1°C warmer than the mean over recent decades (1981–2011,- 16.6°C ± 4.6°C) and also that the mean has been increasing over the last decade. In comparison to the same period, 2010–2011 summer maximum temperatures were 1.4°C (31.6°C ± 2.0°C) higher and the annual mean diurnal temperature range (Tmax−Tmin) was 1.6°C higher (14.7°C ± 0.5°C). In 2009, the year before the forest mortality began, annual precipitation across the study area was 69% less (301 mm ± 38 mm) than the mean of 1981–2010 (907 mm ± 69 mm). Using Système Pour l'Observation de la Terre mission 5 (SPOT-5) satellite imagery captured after the summer of 2010–2011 Evans and Lyons (2013) mapped a broad scale forest mortality event across the Forested study area. This satellite-climatology based methodology provides a means of monitoring and mapping similar forest mortality events- a critical contribution to our understanding the dynamical bioclimatic drivers of forest mortality events.

find the complete article here

 

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