K. Kartawinata

Reduced-impact logging in Indonesian Borneo: some results confirming the need for new silvicultural prescriptions

Abstract Reduced-impact logging (RIL) and conventional techniques (CNV) were compared in a mixed dipterocarp hill forest in East Kalimantan in three blocks of about 100xa0ha each. Damage was evaluated using pre- and post-harvesting assessments in 24 one-hectare sample plots. RIL techniques nearly halved the number of trees destroyed (36 vs 60 trees/ha). RIL’s main benefit was in the reduction of skidding damage (9.5% of the original tree population in RIL vs 25% in CNV). Before logging, mean canopy openness in CNV (three plots only) and RIL (9 plots) was similar (3.6 and 3.1%) and not significantly different (χ2=2.73, P=0.254). After logging, the mean canopy openness was 19.2% in CNV (n=9 plots) and 13.3% in RIL (n=8 plots), and the distributions of the canopy class in RIL and CNV significantly different (χ2=43.56, P 8 trees/ha), both stand damage and canopy disturbance in RIL approached those recorded in CNV under low or moderate felling regime. Over this felling intensity threshold the effectiveness of RIL in reducing tree damage is limited. In mixed dipterocarp forest where harvestable timber density generally exceeds 10 trees/ha, a minimum diameter felling limit is clearly insufficient to keep extraction rates below 8 trees/ha. Based on these new results and previous studies in Borneo, we suggest three silvicultural rules: (1) to keep a minimum distance between stumps of ca. 40xa0m, (2) to ensure only single tree gaps using directional felling, (3) to harvest only stems with 60–100xa0cm dbh. Foresters, policy makers and certifiers should consider these as criteria for sustainable forest management. We emphasise the need to expand harvesting studies to look at impacts and trade-offs across larger forest landscapes, to expand RIL beyond silvicultural concepts and to include the maintenance of other forest goods and services.

The lowland forest tree community in Malinau, Kalimantan (Indonesian Borneo): results from a one-hectare plot

Background: While Borneos forests are globally recognised for their diverse vegetation many regions remain uncharacterised. Aims: We examine the tree community in one hectare of lowland (hill) forest near the Malinau River. Methods: We objectively sited a 1-ha plot in primary forest. All stems over 30 cm girth were measured and identified. Results: Stem basal area was typical for Asian rain forests, but the numbers of stems (759) and species (205) were high. The most abundant species were Gluta wallichii, Cleistanthus bakonensis and Lithocarpus cantleyanus, while those contributing most to basal area were Shorea venulosa, Dipterocarpus lowii and Calophyllum lowii. Dipterocarpaceae was the dominant family amongst the largest stems and contributes a third of stand basal area (11.5 m2). Thirty-three secondary species contribute 24% of stems and 16% of the plots basal area. Conclusions: This is one of the richest hectares of forest trees reported from Indonesia. Species possess broad edaphic preferences and diverse biogeographic affinities. Tree species density likely reflects disturbance history and climatic stability as well as a combination of site factors reflecting the complex local geology, rugged landscape context, and associated edaphic variation. Further botanical explorations in Malinau and other poorly known regions of Borneo are required.