Supervised logging and climber cutting improves stand development: 18 years of post-logging data in a tropical rain forest in Borneo

- Evaluation of long-term effects of two slivicultural practices in tropical Borneo.
- Supervised logging with climber cutting improved ingrowth of dipterocarps.
- Supervised logging with climber cutting reduced the proliferation of pioneer trees.
- Climber cutting lowered overall tree mortality.

We analyzed 18 years of post-logging data from Sabah, Borneo to evaluate the impact of two selective logging methods - Supervised logging (SL) including pre-aligned skid trails and directional felling, and conventional logging (CL), where trees were felled before the crawler tractor was called in for skidding and the fellers had no formal training in felling techniques - on net standing volume recovery, survivor growth, ingrowth and mortality of trees (⩾10 cm DBH). The logging treatments were either combined with- (CC) or without (NCC) pre-harvest climber cutting in a randomized 2 × 2 factorial design consisting 16 one-hectare treatment plots. We investigated the effect on the complete stand including all trees (⩾10 cm DBH) regardless of species, but also distinguished between the effects on the commercially interesting species of dipterocarps (Dipterocarpaceae family) and pioneer species (mainly Macaranga species). Supervised logging in combination with climber cutting was in many ways beneficial to stand development and these effects were mainly expressed at higher harvest intensities. For example, supervised logging reduced the ingrowth and survivor growth of pioneer Macaranga spp.; at high harvest intensities approximately 50% fewer pioneers grew in when SL was used in comparision to CL. In addition, climber cutting increased the ingrowth as well as decreased the mortality of highly valuable dipterocarp species with increasing harvest intensity. These effects appeared also to have stand level consequences as forests treated with the combination of supervised logging and climber cutting also exhibited faster recovery in standing volume of high value dipterocarps compared to any other combination of treatments. We conclude that, with improved ingrowth of dipterocarps, reduced overall mortality and generally better stand volume recovery; supervised logging (SL) in combination with climber cutting (CC) could be an attractive forest management system in mixed dipterocarp forests.