The Susceptibility of Southeastern Amazon Forests to Fire: Insights from a Large-Scale Burn Experiment

Balch, Jennifer K.; Brando, Paulo M.; Nepstad, Daniel C.; Coe, Michael T.; Silvério, Divino; Massad, Tara Joy; Davidson, Eric A.; Lefebvre, Paul; Oliveira‐Santos, Claudinei; Rocha, Wellington Willian; Cury, Roberta T. S.; Parsons, Amoreena L.; Carvalho, Karine S.

doi:10.1093/biosci/biv106

Cited by 110 publications

(117 citation statements)

References 59 publications

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“…Indeed, if burning mostly occurs along forest edges and is also associated with increased access to the forest, all tropical forest edges in all countries are becoming increasingly more exposed to further disturbances. As such there might be different levels of impacts and different causes but there are common ecological consequences such as an increased desiccation affecting forest structure and composition, degradation of these forests, a decrease in living biomass and finally a reduction of their capacity to act as a carbon sink (Balch et al, 2015;Harper et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

et al. 2017

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Abstract. Tropical forests in NW Amazonia are highly threatened by the expansion of the agricultural frontier and subsequent deforestation. Fire is used, both directly and indirectly, in Brazilian Amazonia to propagate deforestation and increase forest accessibility. Forest fragmentation, a measure of forest degradation, is also attributed to fire occurrence in the tropics. However, outside the Brazilian Legal Amazonia the role of fire in increasing accessibility and forest fragmentation is less explored. In this study, we compared fire regimes in five countries that share this tropical biome in the most north-westerly part of the Amazon Basin (Venezuela, Colombia, Ecuador, Peru and Brazil). We analysed spatial differences in the timing of peak fire activity and in relation to proximity to roads and rivers using 12 years of MODIS active fire detections. We also distinguished patterns of fire in relation to forest fragmentation by analysing fire distance to the forest edge as a measure of fragmentation for each country. We found significant hemispheric differences in peak fire occurrence with the highest number of fires in the south in 2005 vs. 2007 in the north. Despite this, both hemispheres are equally affected by fire. We also found difference in peak fire occurrence by country. Fire peaked in February in Colombia and Venezuela, whereas it peaked in September in Brazil and Peru, and finally Ecuador presented two fire peaks in January and October. We confirmed the relationship between fires and forest fragmentation for all countries and also found significant differences in the distance between the fire and the forest edge for each country. Fires were associated with roads and rivers in most countries. These results can inform land use planning at the regional, national and subnational scales to minimize the contribution of road expansion and subsequent access to the Amazonian natural resources to fire occurrence and the associated deforestation and carbon emissions.

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Section: Discussionmentioning

confidence: 99%

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

et al. 2017

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“…Synergies between direct human activities and climate change may accelerate the transformation of tropical forests based on positive feedbacks among ecosystem productivity, regional climate, species composition, and forest disturbances (Brienen et al, 2015;Davidson et al, 2012;Malhi et al, 2009). Forest fires are one potential mechanism for a disturbance-driven dieback of Amazon forests (Balch et al, 2015;Barlow et al, 2016;Cochrane et al, 1999;Longo et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Because the expansion of the fire perimeter over multiple days generates quadratic growth in burned area, these long-duration fires are an essential aspect of fire ecology in the Amazon. Most plant species are poorly adapted to survive even low-intensity fires (Balch et al, 2015;Barlow and Peres, 2008;Malhi et al, 2008). The resulting tree mortality and canopy openings alter the forest microclimate and favor invasion by grass species; combined, changing fuels and microclimate in burned forests can create a positive fire feedback (Balch et al, 2008;Barlow and Peres, 2008;Cochrane et al, 1999;Silvério et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Synergy between land use and climate change increases future fire risk in Amazon forests

et al. 2017

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Abstract. Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, which are common under the current climate in frontier forests, may accelerate Amazon forest losses from climatedriven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactions between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change -Representative Concentration Pathway (RCP) 8.5 -projected understory fires increase in frequency and duration, burning 4-28 times more forest in 2080-2100 than during 1990-2010. In contrast, active climate mitigation and land use contraction in RCP4.5 constrain the projected increase in fire activity to 0.9-5.4 times contemporary burned area. Importantly, if climate mitigation is not successful, land use contraction alone is very effective under low to moderate climate change, but does little to reduce fire activity under the most severe climate projections. These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change.

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“…Based on our experience of tropical savannas and Tasmanian and New Zealand vegetation we suspect that where climate is favourable for forest most forest -savanna mosaics are the result of underlying edaphic factors, with human ignitions sharpening forest boundaries. One key exception is where human fires have destroyed forests and created savannas or grasslands (Cochrane et al 1999;McGlone 2001;McWethy et al 2010McWethy et al , 2014Balch et al 2015). In such 'derived savannas' (Backéus 1992), we suspect that firevegetation-soil feedbacks that cause hysteresis in the loss (fast) and recovery (slow) of forest, potentially exacerbated by seed dispersal limitation, are most likely to be of importance on infertile substrates where nutrient capital is build up in the organic soil horizons.…”

Section: Resultsmentioning

confidence: 99%

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

Bowman

Perry

2017

Plant Soil

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Background Ecologists fiercely debate the role of soil conditions and fire regimes in controlling forest -savanna boundaries. A prominent component of this debate centres on the plausibility and existence of fire-mediated alternative stable state dynamics (FMASS), a model first proposed by the Tasmanian ecologist WD Jackson in 1968. The FMASS model asserts that increased or decreased landscape fire activity, often due to human intervention, can overwhelm physical environmental (e.g. topography and edaphic factors) controls of forest and savanna mosaics, thereby creating landscape dynamism. Many FMASS models include fire-vegetation-soil interactions (FVS), in which changes in fire frequency can change soil fertility and hence tree growth. This interaction, in turn, affects the capacity offorests to recover from disturbance and long unburnt savanna to convert to forest. Scope We evaluate support for the FMASS-FVS model in the context of the dynamics of the Tasmanian forests that have recently been drawn into wider, global debates surrounding the cooccurrence of tree and treeless vegetation states. We develop a simple spatial simulation model to illuminate the difficulties in analysing landscape pattern to draw inferences about the existence of FMASS-FVS. Conclusions Our review of the Tasmanian evidence shows that FMASS-FVS cannot unambiguously explain all tracts of sedgelands in Tasmanian wet forests, and hence Tasmania should not be used as an exemplar of these theories globally. Our simulations highlight that soil sampling that targets forest boundaries risks erroneously concluding that the distribution of forest and savanna boundaries is decoupled from edaphic factors. We describe a structured methodological pathway that can identify the role of FMASS-FVS in Tasmanian forest dynamics, and elsewhere in the world. This approach use cross-scale temporal and spatial analyses, and targeted experimental tests, to illuminate the interplay of fire, vegetation and edaphic factors in controlling tree establishment and growth and forest boundary dynamics.

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The Susceptibility of Southeastern Amazon Forests to Fire: Insights from a Large-Scale Burn Experiment

Cited by 110 publications

References 59 publications

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

Synergy between land use and climate change increases future fire risk in Amazon forests

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

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