Carbon stocks of second growth forest and reforestation stands in Southern Philippines: baseline for carbon sequestration monitoring.

The purpose of this study is to generate baseline quantitative estimates of carbon stocks of natural and common tree plantation species necessary for future carbon sequestration monitoring using permanent monitoring sample plots. Standard sampling techniques and forest/species-specific allometric equations were used to estimate the biomass and carbon stocks of tree plantations and natural stand. The study showed that even without appropriate management interventions, the five stands can store carbon ranging from 112.72 to 226.80 Mg C ha -1 or a total of 914.61 Mg C ha -1 in its biomass and soil comparable to managed tree plantations and natural forest in the country. As observed, frequency distribution for aboveground carbon followed a trend: Second growth forest > Mahogany > Mangium > Teak > Yemane. Of the carbon pools, aboveground biomass obtained the bulk of carbon stored except in Teak stand where most of the carbon was stored in the soil which totally influenced the total storage potential of the site. Teak registered highest in soil organic carbon (SOC) with 134.58 Mg C ha -1 or about three times higher as compared to the SOC of second growth forest and the other tree plantations. It is very interesting therefore to know how appropriate ecosystem management would affect the potential of these stands/forests for carbon sequestration. Introduction. The increasing intensity of weather events and its devastating impacts such as that of the recent super typhoon Haiyan in the Philippines, with reported death toll close of more than 6,000 and total damage of around PhP36.0 billion to agriculture and infrastructure (Cahinhinan 2013), only prove that the threat of climate change remains a serious concern especially among developing countries whose economic means are too limited. This scenario is expected to worsen since the Philippines ranked third in the world and first in Asia in the list of most vulnerable countries to climate change (UNU- EHS 2011). Based on the downscaling made by PAGASA using the Hadley Center's global climate model PRECIS, the country's annual mean temperature is projected to increase by 0.9 o C-1.2 o C by 2020 and 1.7 o C-3 o C by 2050 (PCCC 2009). The impact of this change in temperature is expected to be worst in Mindanao, the country's food basket. Such trend definitely has economic, ecological, and health risks that must be recognized and addressed. While there are viable options for climate change mitigation, mitigation through forestry remains a feasible alternative for the country in reducing net concentrations of atmospheric greenhouse gases (GHGs), especially carbon dioxide, which account at least half of the effect that causes global warming. The wide interest for forests particularly as carbon sink is due to its cost effectiveness, high potential rates of carbon uptake, and associated environmental and social benefits (Moura-Costa 1996). According to Schroeder (1992), about 70% of the entire exchange of carbon that passes through the earth's terrestrial vegetation occurs through the forest ecosystem. However, maintaining the carbon stocks through forest protection is a huge challenge in the country because of the population's overwhelming dependence on forests in terms of goods and services. An estimated 100,000 ha year