Above and below ground biomass was studied in six years old mangrove plantations of Avicenia marina (Am), Avicenia officinalis (Ao) and Sonneratia apetala (Sa) and a naturally regenerated stand under regeneration improving felling operation (NR: consists of Ceriops decandra, Bruguiera sexangula, and Aegicerus corniculatum) protected for seven years since 2000. Common allometric equations were developed for biomass estimation by performing regressions between dry weights of trees as dependent variables and biometric parameters such as stem diameter, height and wood density as independent variables. The above and below ground biomass in NR (70 Mg ha^-1 and 104 Mg ha^-1) was the greatest (P < 0.001), and followed by Sa (69 Mg ha^-1 and 32 Mg ha^-1), Am (25 Mg ha^-1 and 27 Mg ha^-1) and Ao (21 Mg ha^-1 and 26 Mg ha^-1). The total carbon stock in biomass was 73 Mg C ha^-1 in NR, 43 Mg C ha^-1 in Sa, 21 Mg C ha^-1 in Am and 18 Mg C ha^-1 in Ao respectively. The averaged total soil carbon stock up to 1 m soil depth in plantation site was estimated to be 167 ± 58 Mg C ha^-1 which was nearly two times higher than that of current paddy fields 85 ± 17 Mg C ha^-1. These facts suggest the feasibility of mangrove plantations and natural regeneration as a carbon sequestration tool. The induced natural regeneration method showed high feasibility as a low cost management to enhance the rapid restoration of the mangrove ecosystem.

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Long-term observations were conducted over the last 16 years to assess the degradation processes within a secondary forest in an equatorial region in Sumatra Island. Two belt transects representing 5.6 km × 10 m in total and two permanent plots of 1.8 ha were used. A secondary forest located below 300 m in altitude was largely lost over the last 8 years, and this deforestation, which was largely caused by clearing for fields and logging for timber by the local people, expanded to a forest at 500 m in altitude, 3 km from the nearest village. Based on the mortality of the trees with the examined parameters (density and basal area) and distance from the village, we concluded that a secondary forest below 500 m in altitude will be greatly retrogressed within the next 16 years, and the original floristic features of a hill forest below 1050 m in altitude will disapper within next 32 years.

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Masting — the synchronous production of large fruit crops of conspecific trees among years — is a life history strategy in SE Asian tree species. While the reproductive biology of masting is relatively well described, the demographic consequences of masting are poorly understood. Theoretically, irregular production of seeds (masting) is less advantageous than annual fruiting for population growth, even if seed production is proportional to fruiting interval. This is related to the mortality risk between fruiting events, which needs to be compensated by a disproportional increase in seed production in order to maintain the same population growth. To assess the demographic costs of masting for Scaphium macropodum displaying masting behavior, population dynamics of this species in a tropical rain forest in West Kalimantan, Indonesia was studied using a stochastic matrix model. Our stochastic matrix model analyses of different fruiting frequencies revealed a long-term population growth rate of 1.002 for a situation in which fruiting occurs every 16 years. The average masting frequency in the region is higher than this frequency, and we therefore expect populations of our study species to be sustained. Stochastic elasticity analysis suggested that population growth rate was rather insensitive to the level and/or frequency of seed production while it was highly sensitive to adult survival. Stochastic population growth rates were barely reduced when fruiting intervals were prolonged and a proportional increase in seed output was simulated. Hence, if irregular reproduction is combined with increased seed output during fruiting events, the demographic costs of masting may be fully compensated.

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