VEGETATION CARBON STOCKS OF 2–12 YEAR RESTORED MANGROVES IN NORTHERN SUMATRA COASTBAMBANG SUPRAYOGI, SOEMARNO, E. YULI, D. ARFIATI, J. PURBOPUSPITO, G.Y. PANJAITAN, MEILINDA S HAREFA AND ZULKIFLI NASUTION
Restored mangroves at 2, 4, 6, 8, 10 and 12 year old were studied through non-destructive method by measuring stem diameter and tree height of each tree. The objective of this study was to estimate vegetation carbon stocks and its sequestration estimated by three different allometries. The carbon values of restored mangroves were significantly different when it was estimated by different allometries. Average carbon stocks (2 - 12 years) in pondand riverine estimated by D30 2H had a higher value than its estimated by D30 and Destructive Allometry (DA). The carbon stock range in riverine(34.4 â 51.1 MgC ha-1) was higher than the stocks in pond (33.6 - 42.4 MgC ha-1). Carbon sequestration in riverine estimated by D30 increased 34.7% from 18.4 to 50.3 MgCO2e ha-1 yr-1 as the trees growing older. Restored mangroves in this site were able to succeed naturally and grow perfectly in ideal space (1,325 ind ha-1). In contrast, carbon sequestration in pond showed a decreasing trend (-4.4%) from 21.9 to 17.1 MgCO2e ha-1 yr-1. Decreasing trend may relateto competitive factors among individual trees for phosysnthetic process when they grow in dense population (2,596 ind ha-1). The decrease of carbon sequestration of high density restored mangroves is related to the factor of competition between each tree for photosynthesis. The dried twigs leading to dead trees mostly occured at the middle of dense mangroves in pond started at 8-10 years. Combined factors of less nutrient, unstable soil pH, very low salinity and high tree density may influence why the carbon sequestration in pond going to decrease when trees growing older. It is concluded that the carbon sequestration are more influenced by individual tree phenology, species, ideal space (400 - 500 ind ha-1) between trees and their adaptation to different environment rather than by high density (>2,500ind ha-1).