Open access publications in the SLU publication database

Abstract

The tropical rainforests around the world are extremely diverse and support a huge number of timber tree species and have therefore been severely logged. One area that has produced, and still produces, large amounts of timber is Southeast Asia. In this region the most commercially important timber trees belong to the family dipterocarpacae, (dipterocarps). Logging is mostly carried out relatively unplanned and causes therefore great damage to the residual stand. Better planned logging and silvicultural activities, using (for instance) planned skid trails, directional felling and climber-cutting, should reduce the damage and create healthier residual stands. This study tested a logging method involving systematically aligned skid trails combined with directional felling, called supervised logging (SL) and compared it to the conventional logging (CL) practiced in the area. Both logging methods were combined with (CC) and without (NCC) climber cutting. All trees exceeding 10 cm in diameter at breast height (dbh), and a random selection of seedlings and saplings were measured before logging (1992) and for a period of eight years after logging (1993-2001). More trees tended (0.050 < P ≤ 0.100) to be logged where CL was applied than in SL plots (the mean numbers of all stems and dipterocarps logged per ha were 13.0 and 12.4, respectively, in CL plots, compared to 9.4 and 6.7 in SL plots). The skid trail network applied in SL resulted in disturbance to around 7 % of the soil cover. The corresponding figure for the unplanned skid trail network in CL was higher (ca. 10 %), but not significantly different. Climber cutting resulted in four more dipterocarp trees being logged ha-1, compared with NCC: a statistically significant difference (P ≤ 0.050). Basal area lost or severely damaged differed between methods for some diameter classes with mainly CL leading to greater losses. The residual stand contained statistically significantly more dipterocarp seedlings after CL than after SL, while saplings and trees showed the opposite trend, i.e. more individuals were left in the residual stand after SL than after CL. There were significantly (ca. 30%) more 10-29 cm dbh dipterocarp trees in the residual stand after SL than after CL. Cutting climbers had no initial effect on the residual stand in terms of densities of seedlings, saplings trees of either all species or dipterocarps. Data collected during the subsequent period show inter alia, that the net basal area increased at similar rates following both logging methods, considering all species. There was also no significant difference between SL and CL in terms of dipterocarp net basal area, although this parameter grew by 1.0 m2 ha-1 after SL and declined by 0.1 m2 ha-1 after CL. Climber cutting significantly and positively affected net basal area growth, which amounted to 6.4 m2 ha-1 and 3.3 m2 ha-1 in the CC and NCC plots, respectively. The substantially higher growth associated with CC was mainly due to the growth and recruitment of small trees, mainly pioneer species.