The Indonesian natural forest area, according to the Forest Land-use by Consensus (1982), is estimated to be almost 144 million hectares which is about 74% of the land area of Indonesia. From a functional point of view the natural forest has been divided into four types: Protection Forest (31 mill ha); Natural Reserve and Recreation Forest (19 mill ha); Production Forest (64 mill ha) and Conservation Forest (30 mill ha).
Dealing with the natural forest, there are two major forest types in Indonesia, namely tropical rain and monsoon forest. The tropical rain forest is dominated by Dipterocarp family, namely Shorea, Dryobalanops, Dipterocarpus, Hopea, Vatica, Parashorea, Cotylelobyum and Anisoptera species. At present, these are harvested for economical purposes.
Timber harvesting, as one utilisation of the tropical natural forest in Indonesia, is carried out by the silvicultural system, the Indonesian Selective Cutting and Planting (Tebang Pilih Tanam Indonesia/TPTI). The unit of the utilisation is the Forest Concession Right (Hak Pengusahaan Hutan/HPH), where at present there are about 585 HPHs operating in the tropical natural production forest in Indonesia. For the management of the natural tropical rain forest, almost all forest concession holders use the TPTI system. The cutting cycle is presently at 35 years.
Timber harvesting is the most important intervention factor in forest operations and management practices on the environment. Together with the TPTI system, they ensure the survival of the natural tropical forest in Indonesia. The effect of timber harvesting will vary greatly according to the forest stock and random factor such as the relative spacing of crop tree (stand density) and of the skidtrails. Timber harvesting operations need to be carefully planned to achieve expected results, and stock mapping of the timber harvesting is essential.
Conventional timber harvesting, which has been practised until now, often is considered to be a major cause of forest degradation; however shifting cultivation and forest fires frequently are also responsible for forest decrease. The concession holders and/or logging contractors usually carry out their timber harvesting operations in the simplest way, often without sufficiently detailed harvesting plans and work instruction for timber harvesting operations.
Several research results (e.g. Elias, 1995; D.P. Dykstra and R. Heinrich, 1996; J.G. Bertault and P. Sist, 1995; and Abdulhadi et al, 1981) indicate that conventional timber harvesting with insufficient planning, improper operational techniques and lack of control of operation and supervision result in severe damage to soil and residual forest stand; this leads to environmental degradation (damaged forest, erosion, compacted and infertile soil, turbid water and sedimentation, etc.).
Recently, Elias (1996) found that the degree of residual stand damages caused by conventional timber harvesting ranged between 28-45% and incidence of damage to small trees was greater than to larger trees (about 80%). Most of the damaged trees were heavily injured (about 85%) and had little chance to recover because the degree of damage did not permit their survival. In many instances the growth of forest stand (annual increment) would be affected by the damage. Research in logged-over areas has shown that the average diameter growth of commercial trees after timber harvesting with the TPTI system was lower than 1 cm/year as compared with the estimated growth suggested in the regulation of the TPTI system guidelines.
Another research on reduced impact timber harvesting (e.g. Pinard et al, 1995 and
J. Hendrison, 1990) concluded that residual stand damages and opened area caused by conventional timber harvesting can be minimised by means of better timber harvesting planning and proper, well-controlled timber harvesting operation techniques. Detailed information on how to introduce reduced environmental impact timber harvesting is available in the FAO model code of forest harvesting practice (D.P. Dykstra and R. Heinrich, 1996).
The objective of the study is to test the applicability of some of the suggestions made in the FAO Model Code with reference to improved forest harvesting practices in tropical high forests. This research was conducted in the forest concession area of PT. Sumalindo Lestari Jaya IV, East Kalimantan, Indonesia, in 1996, on reduced impact timber harvesting versus conventional timber harvesting operations.