THE STRUCTURE OF LOWLAND RAIN-FOREST AFTER SELECTIVE LOGGING IN WEST KALIMANTAN, INDONESIA

To quantify forest structure following mechanized selective logging in a dipterocarp forest in West Kalimantan, Indonesia, we compared unlog ged forest and sites logged 6 months, 1 year and 8 years prior to samp ling. Forty-one percent of the total area was in swamp forest, interdi gitated with lowland forest. Small patches of lowland forest (15% of l owland area) and 85% of swamp forest escaped logging disturbance. The canopy of 76% of lowland forest was moderately to heavily disturbed by logging; 45% was in open gap or pioneer vegetation. There was only li mited evidence of canopy development after 8 years. In lowland sites l ogged 6 months or 1 year before sampling, forest floor was disturbed i n 16% of area by roads, tractor tracks and skid trails. Local canopy d isturbance increased, but at a decreasing rate, with the amount of bas al area extracted. Dipterocarp trees over 50 cm in diameter at breast height (DBH) comprised 70% of total basal area before logging. The har vest removed 62% of pre-cut dipterocarp basal area and 43% of pre-cut total basal area. Small dipterocarp trees (less than 50 cm DBH, below harvestable size) suffered high mortality due to logging, possibly lim iting future wood production. Logging resulted in a complex spatial mo saic of forest types and disturbance levels, suggesting options for co nservation and management. Swamp forest timber resources, unharvested by conventional mechanized logging, could potentially be hand-logged b y local villagers, increasing both villagers' incomes and revenue to c oncessions. Patches of unlogged forest may sustain some vertebrate and tree species. The detailed analysis of forest structure in this study provides part of the essential information needed to assess sustainab ility of management options. For the modeling of stand development tha t is necessary to develop an ecologically sound management system for dipterocarp forests in Indonesia, additional data on regeneration, tre e growth and survival rates are required.