Abstract
Successive changes of stand structure and primary productivity of a ropical secondary forest from clear cutting were studied through long-term observation during 12 years from 4 years later after the event in a foothill rain forest area of West SumaEa, Indonesia.
Species number of trees over 5 cm dbh at the initial observation ranged from 30 spp. to 40 spp. per a stand being under 1000 m2 in area, and this value was less than half of one in a matuled forest stands with same area. The secondary forest had some prominently dominant species derived from germination after the last logging. Growth rate of biomass was largely different among sites, and a sund on fertile soils conditions grew up to 300 metric ton ha-1 in aboveground biomass within 9 years. Many canopy trees in the forest, however, rapidly died at the latter phase of this observation, and Eees sprouted from logged stumps and species in a matured forest both increased their dominance relatively. Frequent logging would be to the advantage of species having coppice generation because ofpositive correlation between a stump size and growth rate of shoots.
Hardness of stem wood of secondary species tended to be lower than one of matured forest species, and the property had a positive conelalion with relative growth rate of dbh (RGRD) for secondary species. A mathematical model based on this relation suggested that amount of photosynthetic product of a tree would not be largely different irrespective of stem hardness under similar external and internal conditions, and a tree would allocate the product to suitable positions for the growth ofvolume or bulk density based on is life srategy.
A time rend of a primary net productivity had the maximum value within a few years after logging, and tended to be constant. The value at the stable stages was not sigrificantly different from one of a neighboring matured forest, and was estimated at26 - 30 metric ton ha-1 y-1 as total primary productivity including roots. The RGRD - dbh of a stand largely changed with time on regeneration process, and it produced the maximum productivity at the initial stages. Basing on this time rend of this relation, we analyzed successive changes of stand structure and primary productivity under consideration with effecs of stem hardness of a Eee as physical property.
