Reduced Impact Logging

Reduced Impact Logging (RIL) is the implementation of a collection of forest harvesting techniques which results in low levels (20%) of damage to the residual tree stocks, soil and water quality. Sustaining the productive capacity and the environmental functions of the forest.

Logging with the RIL (Reduced Impact Logging) method has been shown to be able to reduce damage to residual stands by 50% compared to conventional logging. Economic factor and widespread use of tractors have contributed to the popularity of RIL compared to other harvesting systems. It has been adopted by the Forestry Department for state-wide implementation since 2000.

RIL is a collection of several harvesting techniques used to minimise damage to PCT (Potential Crop Trees), regeneration and soil, to maintain the forest's production capacity and to protect the environment. There are three stages of operations in RIL, viz:
  1. Pre-harvest operations
  2. Harvesting operations
  3. Post-harvest operations

packagePre-Harvest Operations

Pre-Harvest Operations Details
Preliminary Harvest Planning A prequisitory activity performed in the office making use of a 1:25,000 scale topographic map. 

Information drawn on the Preliminary harvest planning map includes:

  • Coupe or compartment boundary;
  • Proposed road network
  • Riparian and/or stream buffer zones
  • Steep areas above 25°
Area Reconnaisance
  • The purpose is to verify and update information contained in the preliminary harvest plan map.
  • This includes general Information on the location of boundaries, road alignment, entry and exit points, bridges, culverts, stream buffer zones, steep slopes, rock outcrop and other physical features that are verified in the forest.
Harvest Tree Mapping
  • This activity gathers detailed location and distribution of harvestable trees, bridge locations, stream buffer zones, steep slopes, rocky outcrops, cliffs, ravines, and other physical constrains to the harvest operations.
  • This activity is guided by a census plot design (20m x 50m) (figure 1) with roads and SKTs (Skid trails) used as reference points for the baseline of the census plots.
Marking of Harvest Trees This operation is essentially an activity to mark all harvestable trees (60cm to 120 cm dbh) in a comprehensive manner on the ground according to the following rules:
  • Retain prohibited species (hollow trees, wild fruit trees, and other prohibited trees)
  • Retain mother trees as seed source
  • Retain all trees located within riparian reserves and stream buffer zones
  • Retain trees with a top canopy of more than 50% of tree height or a canopy size that will create a gap opening of more than 0.1 ha
Road Planning
  • Proper road planning reduces damage to the forest, constructions cost, maintenances cost, and transportation costs. Road density limited to 1.3% of harvested area
  • Forest road consist of two parts: the sub-grade and the pavement (sub-base, base and surface)
  • Roads are classified as either; main roads, secondary roads and feeder road. All roads to be constructed are marked on the ground
Main Skid Planning
  • Proper planning of skid trails is crucial to minimize damage
  • Skidding is directed away from streams, minimize skidding distance, avoid skidding on steep slopes and crossing streams
  • Skid trails do not exceed 6% of harvested area or 120m/ha.
  • Skid trails are marked on the ground
Comprehensive Harvesting Plan
  • The CHP is a document that contains the harvesting strategies of a particular harvest area, and is used as a guide for logging contractors to organize log extraction activities.
  • The CHP includes: Particular of Licensee, description of areas, forest resources, harvesting prescriptions, estimated log production, estimated logging impact, harvesting rules and guidelines, agreement, list of roads and SKT's, list of trees to be harvested and CHP Map.

Figure 1: The census plot design (20m x 50m) with roads and SKTs (Skid trails) used as reference points for the baseline of the census plots.

Figure 2: The Comprehensive Harvesting Plan (CHP) comprises information of particular of licensee, description of areas, forest resources, harvesting prescriptions, estimated log production, estimated logging impact, harvesting rules and guidelines, agreements, list of roads and SKT's, list of trees to be harvested and CHP Map.

package Harvesting Operations

Harvesting Operations Details
Road Construction
  • Roads are constructed to provide comfort and safety to the user, whilst reducing transportation costs, and minimize soil disturbance.
  • Roads are constructed in accordance with the road design and specifications determined by the SFD from time to time.
Bridges and Culverts
  • Approaches to bridges must be straight and level for a minimum distance of 10 meters on either side.
  • All parts of the bridge must be well anchored to prevent washing away.
  • The stream banks adjacent to the bridge, on both the top and bottom sides, must be stabilized using wings of durable logs, stone pitch or other equivalent construction.
Drainage Drainage constructed in accordance to the following:
  • At change of slopes, with some drains lined with stones, and the provision of slit traps or sumps
  • No drains construction within 50 meters of watercourse, with intermittent discharge to vegetated areas
  • Additional drains to meet the maximum spacing requirement
Directional Felling
  • Only trees marked for harvesting can be felled, with 10% de-selection of harvestable trees to address sustainability. Any vines attached to stem or trailing from the canopy are cut.
  • Trees with loose bark or limbs, trees with signs of rot, or a heavy lean that will damage adjacent trees shall not be felled
  • Adhere to the use of personal protective equipment (PPEs) and safe practices for tree felling
  • The best felling direction is towards or away from skid trails at an angle of 30-45o. If parallel to the skid trails the tree is felled in a direction away from the skidding direction. In the steep areas, the felling direction should be towards the side of the slope.
  • Control of felling direction is accomplished by the undercut made on the side of the felling direction of the stump, insert wedges into the saw kerf when necessary.
Logs Extraction
  • Log extraction operations are conducted to minimize soil disturbance and forest openings
  • Blading is prohibited during log extraction operations by crawler tractors.
  • The log fisher operation utilizes long cables to haul logs out of the forest over distances of 300 m.
Landing Sites
  • Temporary log storage sites where possible constructed on road shoulders.
  • Ideally located on ridge tops to ensure uphill skidding. Landings are sloped 2-3° to allow surface water run-off towards drains.
  • Landing does not exceed 0.18 hectares, and total density of landing do not exceed 0.7% of nett logging area. Landing construction is prohibited in stream buffer zones or riparian reserves

package Post Harvest Operations

Post Harvest Operations Details
Cross Drain Installation
  • Cross drain are constructed along roads and skid trails at an angle of approximately 45º to the alignment, approximately 0.5 meter in height and self- draining into an undisturbed forest floor.
  • Any blockades that adversely affect stream flow as a result of the harvest operation are be removed to prevent undesirable water impoundment, and to allow streams to returned to pre-harvesting conditions.
Bridges and Culvert Removal
  • All temporary stream crossing structures are removed immediately after the completion of harvest operations at the site, except where in the opinion of the SFD officer, this action may lead to additional or increased bank disturbance and stream siltation
  • Removal of temporary bridges to minimize impact on stream flow
Landing Reshaping
  • All landings are repaired to about 25 cm in depth and reshaped to secure adequate surface drainage.
  • Logging debris are redistributed on the landings as a mulch.

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