Abstract ID: 200

Modeling changes in forest structure from repeated exposure to anthropogenic fires

Understory forest fires in Amazonia are an unintended consequence of deforestation and other land-use fires along the agricultural frontier. Although some forest burns every year, recent satellite-based mapping shows that damages from understory fires are more extensive in years when high winds or low rainfall change the amount and moisture content of fine fuels on the forest floor. Changes in canopy cover and tree heights from previous disturbances also influence fire risk in Amazon forests, yet these aspects of forest structure have not previously been incorporated into ecosystem models. We developed a new fire sub-model in Ecosystem Demography, a height-structured ecosystem model, to evaluate the importance of climate, forest structure, and land-use fires on the extent and frequency of understory forest fires in the upper Xingu River basin. We ran four model scenarios under current climate conditions: forest control (1), forest with fire (2), forest with logging (3), and forest with logging and fire (4). Alone, logging or fire did not lead to long-term changes in forest structure, but the combination of logging and frequent land use fires was sufficient to trap forests in a low-biomass state under current climate conditions. Our results suggest that climate controls on fuel moisture appear less important than climate and disturbance-related controls on fuel amount for initiating a positive fire feedback in standing forest in southern Amazonia.

Session:  Fire - Fire, drought, and changes in vegetation structure and composition

Presentation Type:  Oral