MAPPING AND QUANTIFYING POST-FIRE CARBON BUDGET IN AMAZONIA

Global climate change and the large-scale loss of the tropical forests are probably the most urgent of contemporary environmental problems. Some global circulation models suggest that Amazonia may be vulnerable to extreme drying. In the event of increased drought frequency in the Amazon region, the leakage of fires into forests is likely to be the major agent of forest transformation. This process has an important influence on the global carbon cycling by affecting vegetation structure, changing carbon pools and fluxes, and causing feedbacks to the atmosphere, but it is thus far poorly quantified. The lack of systematic information (spatial and temporal) on these processes is a critical limitation when estimating the magnitude of this carbon source and consequent maintenance of the Amazon forest biome and its ecosystem function. Hence, my main research aim in this fellowship is to combine information from multi-temporal satellite images with extensive field data on the component processes of the net ecosystem productivity (NEP) to: (1) Generate the first map of the fire-affected forests in the Brazilian Amazon; (2) quantify the amount of carbon being emitted, absorbed and moved from and among forest compartments at different time-scales and at different fire frequency and intensity; (3) calculate the carbon budget of Amazonian forests taking into account the effect of forest fires, and understand how this variation is controlled by climate and deforestation rates; and (4) understand how the carbon balance varies temporally and spatially because of forest fires. To achieve the aims of this proposal, the first step will be to analyze multi-temporal satellite images to map the scars of forests affected by fire and quantify the frequency and intensity of fire in this areas. A biomass map will be used to identify different forest classes in the Amazon. Finally, the maps will be merged in one single stratified map. This will characterize the spatial variability of fire damage in the region. This map will be the basis for defining the areas that will be investigate in detail in the field and will be also used in a later stage to extrapolate field data to the whole Amazon. The second step will tackle the effect of different fire frequency and intensity on carbon budget. This will involve a compilation of existing field data and in key field sites, direct measurements of the component processes of the carbon balance or NEP, which is the difference between the CO2 assimilated by the vegetation through photosynthesis and the CO2 released by the ecosystem through the respiration process. These measurements will provide detailed information on the amount of carbon being emitted, absorbed and moved from and between forest compartments at different time-scales. Once the data from the different sources have been analysed, the logical next step is to integrate the datasets in order to understand the annual Amazon-wide variation of the component processes of NEP in the fire-affected areas. Two main approaches will be tested initially: (1) a zonal average method, where, an average value of NEP can be associated to each fire class; and (2) a decision tree method, that can be implemented by combining information about the fire classes and empirically-calibrated relationships between NEP and its component processes with rainfall, biomass and forest type. At this stage all the information will be available for calculating the carbon budget of Amazonian forests, taking into account the effect of forest fires. The ultimate goal of this work is to arrive at annual spatially explicit values of uptake, release and the net balance of carbon in fire-affected forest sites in recent years, to quantify the relative influences of the component processes that determine this net carbon balance and to understand how climate variation and human activities through deforestation, affects its spatial and temporal patterns.