Author : Aah Ahmad Almulqu

Summary : Utilization of forests can be well managed if the information about the forest condition are available. The existence of the Kupang Regency, East Nusa Tenggara Province with high biodiversity information still limited. Hence, we need a study to the Kupang Regency of the dry forest, analyze species composition, and structure. And dynamically, it is not well known how this process affects the carbon pools in tree, litterfall, and soil. For a better understanding of the ecosystem services provided by dry forests in semi-arid region, it is necessary to quantify the carbon stock with its behavior associated with the dynamics of these forest resources. Using of system dynamic analysis in this research is an effort to understand complexity of carbon stock behavior of dry forest in semi-arid East Nusa Tenggara.

This study aimed to study the forest structure, composition, litterfall production, and its decomposition in dry forest of East Nusa Tenggara, select the most suitable compatible tree volume equations from several model tested and developed table tree volume for all species in Mutis Timau Protected Forest Management Unit (Mutis Timau PFMU (Binafun, Bonmuti, Letkole, and Oelbanu). This is to develop allometric equations for quantifying biomass storage in tree component (leaf, branch, stem, and root) and quantitatively describe and predict dynamics of carbon stock based on the conservation scenario, different logging systems, and reforestation level.

The results showed that a total of 94 species belonging to 72 genera and 45 families were recorded. Species richness and forest structure were different between sites. Moraceae was the dominant tree family in most sites, particularly for Eucalyptus urophylla. The results suggest controlling the number of species, level on species distribution pattern, silvicultural interventions to pioneer species through thinning liberation, seeding, and planting (pioneer species) could accelerate the tree regeneration of Mutis Timau PFMU in Kupang District, East Nusa Tenggara province, Indonesia.

Litterfall production and decomposition in four different sites of tropical dryforest in East Nusa Tenggara, Indonesia were studied for 12 months. Total litterfall, leaf litter, and branch litter production in all sites was significantly different (p<0.05). The production of total litterfall, leaf litter, and branch litter production was greater in Binafun (2778.125 g m-2 year-1 and 2453.125 g m-2 year-1), Bonmuti (300.437 g m-2 year-1). The annual mean decomposition rate of litterfall increased followed the order of Binafun < Letkole < Bonmuti < Oelbanu (P<0.05), which was positively correlated with the monthly mean precipitation, monthly mean humidity and monthly mean temperature. The turnover rate calculation indicated that forest floor is replaced each year with a turnover time of 1.083 years.

Tree biomass analysis showed that leaf, branch, stem, and root of tree accounted for 7%, 16%, 66%, and 11% of total tree biomass. The average of leaf, branch, stem, root, and total tree biomass (ton/ha) was 0.033±0.016, 0.067±0.034, 0.289±0.082, 0.049±0.023, and 0.441±0.156, respectively. It was also found that the tree biomass with DBH<20cm was 0.039±0.014. All allometric equation models of tree biomass have a high goodness-of-fit as indicated by high of determination value (R2), it indicated a significant linear relationship between biomass and the predictors (DBH and tree height). These models provide accurate estimates of tree components biomass, because they have the low values of RMSE and AIC from almost of tree species.

Based on the results of system analysis with including climate parameters, the highest carbon stock from the conservation scenario was 781.277 ton C/ha (age 100 year), while the lowest only 80.839 ton C/ha under conventional logging (age 100 year). The averages of tree carbon stock from 0 to 100 years ranged between 47.543 ton C/ha (conventional logging) and 256.429 ton C/ha (conservation), while reforestation scenarios represented from 209.908 ton C/ha (reforestation5) to 245.944 ton C/ha (reforestation1). And 65.017 ton C/ha for reduced impact logging scenario.
This pattern also applies in system analysis at plot level. Therefore, it was shown to
be a promising treatment of conservation for all study sites. However, in order to apply
conservation scenario at carbon enhancement project, we should consider several
important factor such as social, climate mitigation, and ecological.