Forest wildfire emissions and carbon uptake in central Andean-Patagonia, Argentina

DEFOSSÉ G.E.; BERTOLÍN, M.L.; URRETAVIZCAYA M. F.

Punta Arenas

Congreso; VIII Southern Connection Congress; 2016

Wildfires are recognized as one of the main sources of CO2 and other greenhouse gas emissions that influence Global Climate Change. In the eastern slopes of central Andean-Patagonia in Argentina, forests grow under a typical Mediterranean climate, and are yearly affected by wildfires of different magnitude. In recent decades, an increase in forest wildfire´s activity in Patagonia has been associated with rises in global warming trends, increased human activity, and the effects of El Niño Southern Oscillation (ENSO). As any other forest ecosystem, Patagonian forests not only emit greenhouse gases during wildfires, but also remove carbon from the atmosphere as post-fire succession proceeds, acting thereafter as carbon sinks. In this presentation, I will show the results of a study about fire emissions and C uptake in three lenga beech forests stands severely burned 40, 32 and 8 yr ago. Forest structure and aboveground biomass and litter compartments in burned and adjacent unburned stands were quantified for each fire. C stocks and GHG released by the fires (CO2, CO, CH4, NO2, NOx and Ce), CO2 removals and mean annual C uptake, were determined by following IPCC guidelines. Total (aboveground plus root) C stock before fires were 301.8, 270.7 and 258.13 Mg C ha-1 for each site, while C losses due to the fires represented about 35% of the total for each of the three sites, respectively. Differences in pre-fire forest structures and biomass explained the values observed on CO2 and other GHG emissions after the fires. At present, the C balance is negative for the three sites. Without any active restoration and considering actual growth rates for each site, the estimated C recovery time is 105.5 yr for the site burned 8 yr ago, 94.2 yr for the burned 32 yr ago, and 150.2 yr for that burned 40 yr ago. By using variable rates of C uptake (which decreased as early succession proceeds), this recovery time will take 182 yr for the site burned 8 yr ago, 154 for that burned 32 yr ago, and 162 yr for the burned 40 yr ago, respectively. Post-fire environmental and site conditions appeared to have a greater influence in lenga beech forest recovery than primary fire effects. Active restoration activities may be necessary to increase C recovery rates and help to re-establish former lenga beech forest landscapes. However, other studies should be conducted to determine the same parameters, and time to recover, for other Patagonian forest types affected by wildfires.