Dinâmica de carbono em floresta explorada e em floresta nativa não explorada na Amazônia

Abstract

The Amazon forest has been increasingly in evidence in global discussions about their role in control of global climate change, both by the ability to emit greenhouse gases into the atmosphere via burning or thinning, how to absorb carbon from the atmosphere by through the growth of the stand. This study analyzed data from three forest inventories conducted in two distinct areas: an unlogged forest belonging to Embrapa Western Amazon in Rio Preto da Eva/AM and the second area is a forest managed experimentally in 1987, belonging to the INPA in Manaus/AM. This work aimed to study the dynamics of forest - increase rates, recruitment and mortality - besides the stock and carbon dynamics in both areas and respond if the intact forest and the managed forest has been acting as source or sink of carbon to the atmosphere. The forest inventories were conducted in the years 2005, 2007 and 2010, in 27 permanent plots of 1 hectare installed in both areas evaluated, which were measured all trees with DBH equal to or greater than 10 cm. Were calculated the rates of recruitment and mortality, DBH, basal area, volume, total carbon stock of vegetation and their periodic annual increments (PAIs). Considering all the trees measured, the average rates of recruitment were 4.9%, 4.8%, 3.7% and 5% for treatments without exploitation and exploitation of 1/3, 1/2 and 2/3, respectively, and the average mortality rates were 3.1%, 6%, 4.8% and 6.7%, for treatments without exploitation and with exploitation of 1/3, 1/2 and 2/3, respectively. The basal area (23.1 m2.ha-1 in 2005, 23.6 m2.ha-1 in 2007 and 23.7 m2.ha-1 in 2010), the volume (345 m3.ha-1 in 2005, 351.3 m3.ha-1 in 2007 and 353.7 m3.ha-1 in 2010) and the carbon content (149.2 t.ha-1 in 2005, 151.8 t.ha-1 in 2007 and 152.6 t.ha-1 in 2010) increased in each every measurement made. However, the statistical difference between these values was not significant, so it was concluded that forests assessed, managed and unmanaged experimentally, were in equilibrium with the atmosphere during the period evaluated. A comparison of the carbon stock of the years measured with the stock pre-exploratory, in 1986, showed that in 2010 the carbon stock equaled the content before logging, meaning the forest recovery. When the analyzes were made without considering the effects of mortality and recruitment, the results were different. The basal area increased from 21 m2.ha-1 in 2005 to 21.9 m2.ha-1 in 2007 and 23.1 m2.ha-1 in 2010, the volume increased from 313.7 m3.ha-1 in 2005 m3.ha-1 to 327 m3.ha-1 in 2007 and 344.3 m3.ha-1 in 2010, the carbon content increased of 136.3 t.ha-1 in 2005 to 141.8 t.ha-1 in 2007 and 148,9 t.ha-1 in 2010. The difference between these values indicate that by disregarding the effects of mortality on the stand, the forest has not been studied in equilibrium, but growing and acting as a sink of atmospheric carbon.