Incêndios rasteiros em florestas sazonalmente alagáveis por água preta na Amazônia: carga de combustível e recuperação lenta

Abstract

One of the most important instruments of deforestation in the Amazon is fire. However, despite not having much human pressure, igapó and campinarana, both seasonally waterlogged forests in the Rio Negro basin, are highly flammable during the dry season. Based on satellite images and field observations, these forests present higher fire propagation and tree mortality then the adjacent lowland forests. We measured the differences in fuel load between these three forest types in order to compare their flammabilities. We tested the influence of sand content and average length of inundation in fuel accumulation in igapó forests. In addition, we address the regeneration of burned igapós with basal area field inventories and Enhanced Vegetation Index (EVI) as a tool for inferring the re-growth of vegetation in these blackwater floodplains. Our results confirmed that campinarana and igapó forests have higher flammability as a consequence of having superior amounts of fuel load, in the form of a peat-like root mat layer above the mineral soil. Only in igapó, fine fuels (< 8cm) were found in large quantities. These forests spend most of year under water or heavy rainfall, thus the presence of fine fuels may be important for their flammability. Moreover, EVI has confirmed to be an adequate tool for accessing seasonally flooded forests regeneration. The burned igapós we studied showed an extremely low resilience, with a slow re-growth 11 years after the fire.