Comparison of carbon benefits between natural and plantation forests in Aurora Province, Philippines

The study was conducted to detrmine and compare the biomass density and amount of Carbon (C) sequestered in the Diap-diapnan sub-watershed for natural forest and in Gmelina arborea plantation forests in the province of Aurora. Data gathering for biomass measurement was done by establishing sample plots to determine the current biomass density and the amount of C sequestered. Stem biomass was determined by allometric equation and from inventoried volume method. Projected biomass density and amount of C sequestered in both forest types for one production period were determined using prediction equations. Benefits transfer method was used to estimate the value of the current and projected C sequestration services for both natural and plantation forest. Results showed that the total biomass densities were 131.3 t/ha and 72.2 t/ha while total C stored were 149.4 t/ha and 125.8 t/ha for natural and plantation forests, respectively. In the studied nat ural forest, the estimate of biomass density and C storage was lower than those found in other studies in natural forests because the study sites were recently logged. Projected biomass densities in one production period were 381.4 t/ha and 369.9 t/ha with C content of 280.4 t/ha and 239.5 t/ha for natural and plantation forests, respectively. The high biomass content in plantation forest was due to the fast growing species planted. However, in terms of C content, there was a very slight difference between the two forest types due to the lower density of trees in plantation resulting in lower C content. The current estimated monetary values of C in the area were US$ 746/ha and US$ 629/ha for natural forest and eight-year-old Gmelina arborea plantation, respectively. The discounted values of C for one population period for both forest types were estimated at US$ 212/ha, US$ 145/ha, and US$ 115/ha for natural forest and US$ 1021/ha, US$776/ha and US$666/ha for plantation fores ts using 8%,12%, and 15% discount rates, respectively. For C crediting, the equivalent CERs [certified emission reductions] for current and projected C stock in natural forest were 548 CERs and 1,029 CERs without intention to trade while there were 462 CERs and 877 CERs for plantation forests. Both forest types contain a huge amount of C in the tree biomass and in the soil and there are monetary benefits for C sequestration services for natural and plantation forests. However, these benefits should be compared to the costs incurred for the management of both forest types.