Estimating Carbon Dynamics in an Intact Lowland Mixed Dipterocarp Forest Using a Forest Carbon Model

Abstract

Intact dipterocarp forests in Asia act as crucial carbon (C) reservoirs, and it is therefore important to investigate the C dynamics in these forests. We estimated C dynamics, together with net ecosystem production (NEP), in an intact tropical dipterocarp forest of Brunei Darussalam. Fifty-four simulation units (plots; 20 m +/- 20 m) were established and initial C stocks were determined via direct field measurement. The C dynamics were annually simulated with a regression model and the Forest Biomass and Dead organic matter Carbon (FBDC) model. The initial C stock (Mg C.ha (-1)) of biomass, litter, dead wood and mineral soil were 213.1 +/- 104.8, 2.0 +/- 0.8, 31.3 +/- 38.8, and 80.7 +/- 15.5, respectively. Their annual changes (Mg C.ha(-1.)year(-1)) were 3.2 +/- 1.1, 0.2 +/- 0.2, 3.7 +/- 6.1, and -0.3 +/- 1.1, respectively. NEP was 0.6 +/- 6.1 Mg C.ha(-1).year(-1), showing large heterogeneity among the plots. The initial C stocks of biomass and dead wood, biomass turnover rates and dead wood decay rates were elucidated as dominant factors determining NEP in a sensitivity analysis. Accordingly, investigation on those input data can constrain an uncertainty in determining NEP in the intact tropical forests.