Ground skidding timber harvesting is the most common timber harvesting system (almost 90 %) in use in the TPTI system, especially by bulldozer or crawler tractor skidding. It is estimated that in the future the system will be continually operated in the tropical natural forest in Indonesia, considering that the mastery of another more environmentally-oriented timber harvesting technology and technique (e.g. cable and helicopter timber harvesting) is still inadequate, and the operational costs of the system are very high.
Research on reduced impact timber harvesting with the TPTI system in the tropical natural forest in Indonesia indicates that conventional timber harvesting with insufficient planning, improper operational technique and lack of control of operation and supervision will cause heavier damage to soil and residual stand, which consequently lead to environmental damage.
As compared to conventional timber harvesting, on the other hand, reduced impact timber harvesting can lessen damage up to 50 % - without a significant productivity decrease - through a series of timber harvest plans and techniques, such as: cutting of vines before felling, regulation of felling direction, skidtrail planning and construction, proper skidding and an overall timber harvesting efficiency.
Research results demonstrate, furthermore, that reduced impact timber harvesting is not necessarily more expensive than conventional timber harvesting, moreover economically profitable, because timber damages value caused by conventional timber harvesting is twice than the timber damages value caused by reduced impact timber harvesting and the latter will consequently enhance future forest productivity and reduce the cost associated with potentially adverse off-site consequences of timber harvesting. When using this system, it is important that operations be well supervised and that the quality, as well as the quantity, of work be controlled.
To accomplish the above situation, it is necessary to promote the implementation of reduced impact timber harvesting within the TPTI system in the tropical natural forest in Indonesia. Available information is sufficient, such as information on management practice, stand conditions, harvesting techniques and costs. A major obstacle is the absence of large scale topographic maps for areas to be harvested. The existing topography maps are still inadequate for reduced impact timber harvest planning and related road engineering work. It is recommended that proper topography and tree location maps be prepared with a scale of 1 : 2,000 and 5 meter contour line intervals, upon which initial hauling road, skidtrail, landing and camp location are indicated.
To guarantee a successful implementation of reduced impact timber harvesting, it is also recommended that guidelines be prepared for insertion of reduced impact timber harvesting within the TPTI system in the tropical natural forest in Indonesia; that training be conducted for chainsaw operators/fellers, tractor operators and felling and skidding foremen and timber harvesting supervisors and planners; that further research be encouraged to reduce environmental impacts in the tropical natural forest while simultaneously improving productivity and reducing harvesting costs, e.g. alternatives to tractor timber harvesting on steep slope, namely skyline or helicopter timber harvesting, which already have been put into practice several years ago in tropical natural forests in Malaysia and Indonesia.
