Fire Damage in Seasonally Flooded and Upland Forests of the Central Amazon

Abstract

Neighboring upland and nutrient‐poor seasonally flooded Amazon forests were penetrated by a fire in 2009, providing a natural comparative experiment of fire damage for these widespread forest types. In upland, only 16 ± 10% (±2 SEM) of stems and 21 ± 8% of basal area were lost to fire, while seasonally flooded forest lost 59 ± 13% of stems and 57 ± 13% of basal area. Drier understory contributes to greater flammability. Much of the area occupied by seasonally flooded woody vegetation (>11.5 percent of the Amazon region) is vulnerable to fire due to high flammability and slow recovery.

Floodplains as an Achilles’ heel of Amazonian forest resilience

“…Second, our results imply that if the climate becomes drier, fire-prone savannas might expand through floodable areas toward the core of the Amazon forest and become sources of fires that may spread to large parts of that region. Indeed, the spread of fires from floodplains to adjacent uplands has been shown in Africa (28) and central Amazon (22) with negative impacts on vegetation structure (22) and biodiversity (29). In conclusion, our results suggest that seasonally inundated forests throughout the Amazon represent an Achilles' heel when it comes to resilience of this massive system.…”

“…Another reason that makes floodplain forests more vulnerable is their naturally higher flammability compared with upland forests. In addition to having a slightly more open structure (22,23), upon the annual retreat of the waters, floodplain forests typically have large masses of exposed root mats (24) that burn easily and may spread fire effectively in drier years (6, 7) (Fig. S6).…”

Contrasting fire damage and fire susceptibility between seasonally flooded forest and upland forest in the Central Amazon using portable profiling LiDAR

“…Seasonally flooded forest is restricted to the upper half of the annual flood range, which conveniently minimized the effect of inundation duration on forest structure and composition across all flood forest plots. More site details are provided by Resende et al (2014).…”

“…As an indicator of susceptibility to fire establishment, Resende et al (2014) compared the microclimate near the litter layer in unburned black water flood forest, at low water stage in the late dry season, to the litter layer microclimate in adjacent unburned upland forest. They found lower extremes of relative humidity and higher temperature extremes in the flood forest.…”

“…Here we expand on the work of Resende et al (2014), using new data for the burned and unburned black water flood and upland forest plots of that Central Amazon study. Aboveground structural attributes were measured with a portable profiling LiDAR (PPL) (Parker, Harding, & Berger, 2004;Stark et al, 2012).…”