Estimates of Carbon Stock Loss and Annual Carbon Emissions

Biomass values were obtained based on the forest type indicated at each location by the vegetation map of the IBGE (Brazil, IBGE 1992) and the dry mass value above ground and below ground for each forest type calculated by Nogueira et al. (2008a). For areas of forest with a predominance of bamboo, which is abundant in Boca do Acre (Nelson et al. 2006), we used the methodology presented by Vasconcelos et al. (2013). This methodology uses the values for biomass of trees and palms with diameter at breast height (measured 1.3 m above the ground or above any buttresses) greater than 5 cm (Nogueira et al. 2008b), and adds the values obtained from the biomass equations developed by Nelson et al. (1999) for bamboos and by Gehring et al. (2004) for lianas, applied to the inventory carried out in Acre by de Oliveira (2000). Finally, necromass values are added (Nogueira et al. 2008a), obtaining the total biomass for the forest type with predominance of bamboo.

To determine the loss of carbon stocks, biomass values above ground and below ground were multiplied by the average proportion of carbon in dry biomass as determined by da Silva (2007). This proportion is 0.485.

The calculation of annual emissions included the secondary vegetation biomass based on the mean biomass growth rate of secondary vegetation found in abandoned cattle pastures in the municipalities of Paragominas and Altamira, Pará (Fearnside and Guimarães 1996). The average age of secondary vegetation was considered to be 5 years (Almeida 2009). Carbon was considered to represent 45% of the dry biomass of secondary forest (da Silva 2007).