Fire in Australian savannas: from leaf to landscape

Abstract

Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.

Rapid response of habitat structure and aboveground carbon storage to altered fire regimes in tropical savanna

“…Our results highlight the impact of late season burning on both carbon storage and on canopy vertical profile heterogeneity. Clear relationships between biodiversity and fire regimes have proven difficult 10 to establish in savannas, despite many attempts at linking floral and faunal diversity directly to fire regime patterns. The range of vertical profile responses that we have illustrated here under different experimental fire treatments could hold the key to unlocking stronger links between fire management and biodiversity responses.…”

“…Fire frequency in Australian savannas is particularly high, with many regions burning twice in every three years on average (Beringer et al, 2014). Many of these fires occur late in the dry season, producing high intensity burns that result in simplified 10 vegetation structure (Bowman et al, 1988;Lehmann et al, 2009;Ondei et al, 2017).…”

“…Many of these fires occur late in the dry season, producing high intensity burns that result in simplified 10 vegetation structure (Bowman et al, 1988;Lehmann et al, 2009;Ondei et al, 2017). There are widespread concerns that such fire regimes are linked to dramatic declines in faunal populations, through the removal of ground layer vegetation (Lawes et al, 2015;Legge et al, 2015;Woinarski et al, 2015).…”

Describing rainfall in northern Australia using multiple climate indices

“…This area has the potential to increase in size due to climate change (Franchito et al, 2011), making the improved knowledge of these landscapes important in understanding future rainfall trends in Australia and around the world. Australian savannas remain fairly undisturbed (Beringer et al, 2014), making them good for temporal change studies. Vegetation productivity, and hence the carbon balance, is vulnerable to changes in rainfall variability (Kanniah et al, 2011) because savanna structure, composition and function shift in response to shortterm (monsoonal) and long-term (ENSO, Interdecadal Pacific Oscillation, Pacific Decadal Oscillation Index (PDO), etc.)…”

“…Moreover, disturbances, such as fire, cyclones and grazing, are also key drivers of savanna structure and productivity which are in turn driven by rainfall patterns Bond et al, 2003;Hutley et al, 2013). Savanna grass productivity is very sensitive to rainfall and the biomass produced creates fodder for cattle and fuel for frequent burning, resulting in greenhouse gas emissions (Beringer et al, 1995(Beringer et al, , 2014Moore et al, 2015Moore et al, , 2016. Therefore, evaluating the relationship between interannual variation in rainfall and climate phenomena is crucial for predicting the responses of the water, energy and carbon cycles of savanna vegetation (Beringer et al, 2011a;Kanniah et al, 2013).…”