Regardless of the type of logging equipment used in a particular ground-skidding system, the extraction of logs is a difficult, often hazardous operation that can inflict substantial damage on forest ecosystems (Dykstra & Heinrich 1996). The three most common types of damage caused to forest ecosystems during extraction with ground-skidding equipment are:
· Soil disturbance and soil compaction
· Damage to streams, in particular when crossing watercourses during extraction, but also indirectly through the introduction of sediments or spilled fuel and lubricants
· Damage to residual trees and other vegetation
However, all of the detrimental impacts of timber extraction can be reduced substantially by meaningful, comprehensive planning coupled with an effective system of operational control, to ensure that the plan is followed and adapted as necessary in response to changing conditions (Dykstra & Heinrich 1996).
Generally speaking, the following should be considered to allow extraction operations to be conducted efficiently and safely, as well as in an environmentally sound way:
· Appropriate size and power configuration of logging equipment, adjusted to the actual needs of the system applied and with respect to stand and terrain conditions
· Appropriate equipment with respect to technical and safety standards, as well as ergonomic principles and requirements
· Machine operators to undergo skill testing before field work after adequate training
· Well-planned skidtrail layout followed by correct alignment of tree stems with respect to extraction routes to facilitate extraction without major problems for the extraction crew and machines
· Clear instruction to and close supervision of the extraction crew, both internally by the logging supervisor and externally by the PNGFA project supervisor
Whereas the first two points of the above list are widely accepted, the others are still generally neglected. The ground-skidding equipment itemised below are used for log extraction by SBLC and VFP, respectively.
Machine type |
Power |
Weight |
Width |
Activities |
Caterpillar 527 tracked skidder |
112 kW |
17.7 t |
2.7 m |
skidtrail opening and skidding of logs |
Caterpillar D6D crawler tractor |
105 kW |
14.3 t |
2.4 m |
skidtrail opening and skidding of logs |
The CAT D6D and CAT 527 tractors are used to open the marked skidtrails for log extraction, to drag logs to the skidtrails, and to deliver them to the landings. The tractors are also used to establish the landings as specified and approved in the set-up plan, and marked in the field by the inventory crew.