7.1 Tree Marking
7.2 Locating Log Landings and Skid Tracks
7.3 Skid Tracks
To mitigate the negative impacts on biodiversity and improve the production of forests through appropriate silvicultural prescriptions.
To minimise impacts on the residual forest stand and soil and
a joint field inspection of the area;
all buffer zones are marked to the satisfaction of the Supervising Forest Authority Officer;
the contents of the Operational Plan have been discussed and are understood by the Company Supervisor.
NOTE: The Company Supervisor should be a person who will be present and responsible for the operations on the harvest area during the time that operations are in progress.
Most forest harvesting in the Asia-Pacific region uses selection harvesting techniques.
To ensure only appropriate trees are harvested, in a manner that is consistent with maintaining a vigorous forest.
To maintain desirable species composition of the forest after harvesting and a viable residual stand.
To minimise canopy openings in areas where they would allow
the development of vines, weeds and lower-value pioneer species.
Where it is desired to promote the growth of climax species, the size of an individual canopy opening in any one position should be minimal.
The number of trees per hectare selected for harvesting will depend on tree marking rules and the silvicultural system (cutting limits, need for seed trees, etc.) developed for the particular forest type and stand condition.
Before felling operations commence, harvesting company operations staff (including supervisors, tree marking staff and chainsaw operators) must:
- have copies of tree marking rules; andMinimum standards for tree retention
- understand how they are to be applied.
Where desirable species are present in the sub-merchantable size categories:
- identify, protect and retain sufficient numbers of stems to ensure a viable residual stand;Where desirable species do not exist in sufficient numbers, retain the original number and ensure that sufficient quality seed trees are preserved to provide for sustained regeneration.
- appropriate potential crop trees should be marked for retention; or
- silvicultural prescriptions approved by the Forest Authority should be applied.
Minimum standards for cutting
Select only those trees that will provide logs suitable for processing. These must be of suitable species and have the minimum specified log length.
To locate landings and skid tracks appropriately.
To minimise the size of landings to reduce the loss of productive forest area.
To construct and manage log landings and skid tracks to prevent sedimentation of watercourses.
To stabilise log landings and skid tracks after use.
Landings are to be located:
- outside areas excluded from harvesting;Roadsides may be used if:
- at least 40 metres from the edge of buffer zones (Figure 7-1);
- at sites that accommodate skidding patterns and directions;
- to balance site disturbance with skid distance;
- in dry areas on ridges or benches;
- in areas that are easy to drain;
- in areas of low slope to reduce the amount of side cutting;
- located on ridges to promote uphill skidding to disperse runoff into surrounding vegetation (Figure 7-2).
- this reduces earthworks; andThe location of all landings must be shown on the harvesting plan and inspected by the Forest Authority Officer before construction.
- landing areas and roads can be drained adequately.
The Forest Authority Officer may approve additional landings after field inspection.
Figure 7-1: Log Landing Location
Log landing size applies to the working surface of the landing and does not include area for log storage.
The size of log landings includes:
- the total area of disturbance, including cut and fill batters;Suggested maximum log landing size is 900 m2.
- half the road width if the landing is constructed at the roadside.
Landings should be located so that mud and debris do not enter watercourses.
Landings should be located so that free drainage occurs at all times. Ideally landings should be located on gently sloping elevated areas.
Split-level landings may be used to reduce excavation. Safety must be paramount in design of split-level landings as often found with skyline yarding systems.
Mark boundaries of the landing including cut and fill areas.
Remove all merchantable trees.
Construct and maintain landings to prevent the ponding of water.
Drains must empty on to stable vegetated areas.
Where landings are to be used in wet weather, they should be corded using small logs of unmerchantable species (Figure 7-3).
Figure 7-2: Log Landing Construction
Figure 7-3: Log Loading on Corded Landing
Landings should not be bladed off to keep them operational without the approval of the relevant Forest Authority Officer.
Debris and waste heaps should be:
- placed so as not to restrict drainage of the landing;Soil and vegetation debris should be kept separate.
- stored away from standing trees;
- more than 10 metres from drainage areas.
Landings should be restored so that proper drainage occurs to reduce soil erosion and runoff.
If corded, cording should be removed.
Landings should be drained to promote natural revegetation, or replanted with a cover crop and/or:
- ripped at 90° to the drainage direction;Bark and landing debris should be disbursed evenly across the landing to assist in stabilisation.
- ripped radially;
- a berm should be constructed around the landing.
The site should be cleaned of non-biodegradable material and all solid waste removed, including oil/fuel drums and wire rope.
Skidding to landings
Skid tracks should usually approach landings from below to avoid directing runoff of water to the landing.
Limits on operation
Avoid the use of logging equipment on saturated soils to minimise erosion, ponding, mixing and compaction of the soil and minimise adverse effects on water quality.
Avoid hauling on wet, rutted roads to reduce excessive turbid runoff that may adversely affect water quality.
A complete closure of forest operations including hauling should be considered in extreme conditions where there is risk of environmental damage.
The number of skid tracks and depth of rutting should be minimised.
High-intensity skidding traffic should be confined to planned tracks that should be located on high ground so they drain naturally.
To minimise the area covered by skid tracks to maintain the productive forest area.
To reduce soil damage along skid tracks.
To minimise damage to watercourses.
To minimise skid track grades (generally <20%).
To locate skid tracks to:
minimise the number of watercourse crossings;
Major skid tracks
Major skid tracks will have more than 10 passes of the skidding machinery along each track. Their construction may require minor earthworks. They will usually be located along spur lines (ridges) to facilitate drainage.
Minor skid tracks
Minor skid tracks will have less than 10 passes of the skidding machinery along each track. Their construction does not require earthworks. Litter is to be maintained on the surface of the track (Figure 7-4).
Uphill or downhill skid
Skidding direction should be decided by the Forest Authority Officer. However, where possible, skidding should be carried out uphill. Skid tracks are based upon assessment of the following factors:
road and landing location (upper slope, lower slope);Winching
watercourse crossings (to be minimised);
potential damage to soil caused by skidding machinery (minimise);
uphill skidding of large logs, with the butt end of the log raised, is likely to cause less soil damage than downhill skidding;
soil types and conditions will affect machine traction and therefore skid direction.
Logs should be winched the maximum distance possible, to reduce the length of soil disturbance associated with skid tracks. Winches should be fitted to all machines with a minimum length of wire of 30 m (18-40 mm diameter).
Skidding in areas excluded from harvesting (other than at defined watercourse crossing points) should not be permitted.
Location of landings should be undertaken prior to the location of skid tracks.
Locate skid tracks:
- away from waterways and unstable areas;Watercourse crossing points for major skid tracks should be shown in the harvesting plan and approved by the Forest Authority Officer. An increase in the number of watercourse crossings will require the approval of the Forest Authority Officer following a field inspection.
- on spur lines where possible, to allow good drainage;
- to avoid damage to residual trees;
- in a way that makes use of sacrificial trees to be removed as protection for trees that are to be retained.
Where major skid tracks must cross slopes, the angle of the skid track to the contour should not exceed 100%.
Advisable maximum slope for side cutting is 50%.
Advisable maximum allowable grades for skid tracks are:
- Major skid tracks
- Minor skid track
45% (D7 controllable limit).
Figure 7-4: Skid Track Construction
Major skid track locations should be inspected and marked in the field prior to their construction and according to the Operational Plan.
Departures from the planned alignment, which involve increased side cutting or increased watercourse crossings, are to be referred to the Forest Authority Officer for approval before construction.
Skidder and chainsaw operators should to identify and inspect the proposed skid track locations prior to commencing construction.
Timing of construction
MAJOR SKID TRACKS
Major skid tracks should be constructed close to the start of felling operations.
MINOR SKID TRACKS
Minor skid tracks should be marked prior to harvesting to assist the cutter to determine the direction of felling. They may be constructed after felling.
No blading if slope is less than 25%.
Construct skid tracks in dry weather.
A maximum skid track width of 4 metres for all skid tracks (width of blade) is suggested.
Avoid side cutting of major skid tracks whenever possible.
Side cutting is not permitted for minor skid tracks.
Side-cut skid tracks should have an out-slope of 2-6%.
Box cuts should not be permitted.
Berms on the outside edges should not be permitted.
The radii of curves should be large enough to prevent damage to retained trees and regeneration unless a sacrificial tree is used.
Drainage should be carried out as required to prevent the build-up of running water.
Skid track rehabilitation
As soon as skid tracks are no longer required for harvesting, proper drainage, using cross-drains, should be installed.
Cross-drains should be constructed to divert water away from the skid track (Figure 7-5).
The distance between cross-drains should be decreased:
- as the gradient of the skid track increases;Maximum Cross-drain Spacing
- as soil erodibility increases;
- if harvesting is to be done in the wet season;
- in areas of high rainfall.
Any watercourses inadvertently diverted into skid tracks must be restored to their original course.
Seriously rutted skid tracks should be restored by backfilling and constructing cross-drains.
Cross drain spacing
Major skid track crossings should be shown on the harvesting plan, and approved in the field by the Forest Authority Officer.
Skid tracks should not cross Class 1, 2 or 3 streams.
Select crossing points on waterways in places where:
- bank slope is less than 18% (preferably less than 9%);Skid tracks should cross watercourses at right angles.
- the bed is firm.
Temporary crossings should be provided to cross gullies, or waterways if water is flowing at the time of operation.
Construct crossings in dry weather.
Width of the crossing is to be less than 4 metres. Buffer vegetation is not to be otherwise disturbed.
Use unmerchantable logs for the crossing where appropriate.
Abutments and approaches should be higher than the stream banks.
Cording of the approaches to the crossing may be required within 2 metres of the high bank.
Soil should not to be pushed:
- past the high bank;Removal
- into watercourses;
- onto the top of the crossing.
Crossings should be removed in dry weather. Crossing material is to be placed more than 10 metres from the high bank.
Removal must not disturb the watercourse banks.
Limits to construction
Wet weather restrictions apply.
Crossings should not be constructed during wet periods.