Several harvest methods are available including one, or a combination of –
- Ground based, such as tractor or rubber tyred skidder
- Cable system
- Aerial extraction by helicopter.
Issues to consider when choosing a harvesting system include –
- Selection method of single tree, small group or coupe of specified size.
- Steepness of site
- Environmental considerations such as the potential for soil and water damage.
Combined with the above are the requirements of the Resource Management Act, especially the requirements of regional and district plans and consideration of extraction method, roading and skid track patterns and costs.
On reasonably flat country with less than 15 degree average slope, ground extraction is less expensive. On steeper country helicopter extraction, although more costly, is better. Small haulers may have a role in some places.
Ground harvest methods using horse and mini skidder which have low impact on the environment also have low production potential. They are applicable in small scale operations where the value of the timber is moderately high. Hauler systems have high productivity, but the greater impact on the environment restricts their use in continuous cover forestry. Skidders, which can also have negative environmental impacts, are only applicable on flat and easy country. On balance helicopter extraction is best, not only because of minimal damage to other plants and the soil, but also because the need for road construction is greatly reduced. However timber value must be reasonably high to permit helicopters to be economic.