Monitoring carbon and COsub2 sequestration potential of large leaf mahogany (Swietenia macrophylla King) and Dipterocarp plantations in Mt. Makiling Forest Reserve [College, Laguna, Philippines]

The two-year study on Monitoring Carbon and CO2 Sequestration Potential of Large Leaf Mahogany (Swietenia macrophylla King.) and Dipterocarp Plantations in Mt. Makiling Forest Reserve was conducted through the support of UPLB Basic Research Program. The study was an offshoot of an earlier study conducted in 2000 on carbon estimation of the same plantations. It was continued to look into the sequestration rate of the plantations which was not considered in the earlier study due to time limitation. This study aimed to: 1) measure the aboveground, necromass and underground biomass accumulation of the two plantations; 2) determine the amount of carbon and CO2 stored in the biomass and soils in both plantations; and 3) determine the rate of carbon sequestration in both plantations by comparing the 2000 data versus 2010 data gathered from the same study sites. This study followed the same methodology on sampling and data collection procedures applied in the 2000 study. Complete inventory of trees with diameter at breast height (DBH) greater than or equal to 5 cm including measurement of total height and merchantable height were done within a 10 m x 50 m transect. Similarly measurement of coarse woody debris (CWD) both felled/thrown and standing dead trees were done in the same 10 m x50 m transect. Purposive sampling was applied for understorey/herbaceous vegetation by harvesting all vegetation within a 2mx2m sampling plot. Necromass or littercrop were collected in a 1mx1m plot. While soils were sampled in a pit with a dimension of 20 cm x 20 cm x 30 cm depth. Fresh weight and oven-dry weight were measured in the understorey and necromass samples while bulk density was measured for the soil samples to determine its biomass and carbon storage. Except for the computation of tree biomass, carbon and CO2 content, the study used the new formula for estimating the carbon and CO2 content of trees and roots. Hence, the authors recomputed the 2000 data using the new formula particularly for roots proposed by Pearson, T. S. Walker and S. Brown, (2005) and for CO2 storage to maintain uniformity of results and make them comparable to the recent data gathered. Results showed that Large Leaf Mahogany stand has a total biomass production of 1,120 mg/ha which is equivalent to 542 mg/ha of C and 1,989 mg/ha of CO2 stored in its biomass. Meanwhile, Dipterocarp stand has a biomass accumulation of 1,047 mg/ha, C amounted to 556 mg/ha and CO2 at 2,039 mg/ha. Both stands showed a comparable rate of C and CO2 sequestration per year. Over a 10-year period, Mahogany plantations registered a biomass build up of 43 mg/ha/yr and sequestered carbon at 22 mg/ha/yr and 81 mg/ha/yr of CO2 while Dipterocarp plantation accumulated biomass at the rate of 39 mg/ha/yr and sequestered carbon at 21 mg/ha C and 77 mg/ha of CO2. Based on the results, the storing capacity and sequestration potential of both plantations to assimilate carbon and CO2 from the atmosphere are more than the capacity of old growth forest, natural stand and other types of vegetations. It was further deduced that the potential forest plantation to sequester carbon can be maximized given a good-site condition, appropriate silvicultural practices applied, less human disturbances or impacts and allowing the stand to attain its optimum growth.