Dynamics of aboveground big woody organs in a foothill dipterocarp forest,West Sumatra,Indonesia

The dynamics of aboveground big woody organs over 10 cm diameter was studied at a mature foothill dipterocarp forest in West Sumatra. The biomass of big woody organs was estimated to be 519 m³ ha⁻¹ or 408 metric ton ha⁻¹ by means of a pipe model theory. The diameter distribution showed a convex curve and the mode was found at a diameter of about 20 cm. The standing mass of big dead woody litter on the forest floor was 116 m³ ha⁻¹, which accounted for 22% by voume or 9.5% by weight of the biomass of living organs respectively. Thedbh observation with two 1-ha plots for 4 yr and 5 yr respectively revealed that the average net production rate was 9.5 ton ha⁻¹ yr⁻¹. The death rate (7.9 ton ha⁻¹ yr⁻¹) accounted for 83% of the net production rate and was nearly equivalent to the decay rate (7.5 ha⁻¹ yr⁻¹) of dead wood on the forest floor. The balance between the death and decay rates was confirmed for each diameter class. Average turnover periods for big woody organs and dead woody litter were estimated to be 43 and 8.1 yr, respectively. Standing masses of live anddead woody materials accumulated in the study forest were approximately equal to those obtained in a mature tropical lowland rainforest, whereas the flow rates were lower, being only 70% of the corresponding values.