Estimating carbon storage and sequestration of Philippine forest ecosystems

Climate change or global warming is one of the most urgent environmental issues of the present generation. Land-use change and forestry (LUCF) activities are important contributors to the problem as well as its solution. Vital information necessary in assessing the role of LUCF in climate change is an accurate estimate of carbon (C) stocks and rate of C sequestration of forest land-uses. The paper reviews the various method available in obtaining an accurate estimate of C stocks and sequestration based on the experiences of the Environmental Forestry Programme (ENFOR) of the University of the Philippines Los Banos [College, Laguna, Philippines]. There are two general methods in estimating C stocks, namely indirectly (based on existing information) and directly (based on field data gathering). The indirect estimation of C stocks in the forest is premised on the fact that about 50% of biomass is C. There are already existing "default" values for all the major ecosystems in the tropics. This paper provides an example of how these can be used to estimate national C storage and sequestration in LUCF. Field measurement of C involve destructive sampling or combining destructive sampling with the use of allometric equations for large trees developed by Brown in 1997, Y = exp (-2.134 + 2.530* In (D)) where Y = biomass per tree (kg), and D = dbh(cm). ENFOR has adopted methods for natural tropical forests, tree plantations, agroforestry, brushlands, and grasslands using a combination of small plots with measurements of 10 x 100 m, 10 x 10 m, 10 x 20 m (multistorey agroforestry), 10 x 10 m and 1 x 1 m, respectively. Carbon pools monitored include aboveground biomass (trees, understorey vegetation, herbaceous plants), litter/necromoss, belowground biomass (roots) and soil organic C. The paper also discusses the role of models and remote sensing as useful tools in estimating C stocks and sequestration of various C pools. Finally, important issues and concerns that need to be addressed are identified