After years of careful management, the time has come to fell or harvest the final timber crop. That may be as short as 12-15 years for poplars, or around 40 years of age for conifers like pine, larch and Douglas fir and quick growing broadleaves like wild cherry. Many broadleaves such as oak and beech can take 120 years before they become of timber value.
The timber is normally sold either:
- Standing - when the person the trees are sold to is responsible for felling them.
- Or at stump where the trees have been felled but someone else then comes along and extracts them to take them away.
- Or at roadside where the owner has been responsible for harvesting the trees and extracting them to the roadside ready to take away.
Modern timber harvesting requires proper planning and a high degree of operator skill. Many machines used nowadays are technologically advanced, state of the art, expensive machines. Harvesting is not a job for amateurs.
Nowadays fewer and fewer large forestry enterprises employ their own direct labour. Having your own trained operators, providing adequate equipment and finding work for them all year is challenging and not often cost effective. The trend is towards outside contracted labour for harvesting.
As with harvesting any crop, wasted time and effort equate to wasted money. Careful planning is necessary. Factors to remember include:
- The terrain - is it flat, steep, wet, rocky or what?
- The forest crop itself - are you dealing with very big or tall trees, are you taking all or just some of them?
- Markets - what type or size of products do your customers want?
- Machinery - some of the specialist forestry machinery around is only economically viable to use on large programmes and intensive use so it may be ruled out for those reasons.
- Tree-length system. In the past, most timber felled in Britain was harvested by this system. Once felled, the tree is delimbed at stump, extracted to roadside and then cut into sawlog lengths and other products; these products are then sorted and stacked for collection by lorries.
- The shortwood system is where felling combines delimbing with cross-cutting at stump so that all that is extracted are the saleable products and all waste is left in the forest.
- Mechanical harvesting is now increasingly common. Many of the top of the range machines cut, hold, delimb and cross-cut trees to the required product lengths within seconds.
- Horse Logging. There has been a resurgence in using horses for logging operations in forestry over the last couple of decades, particularly in difficult, small or sensitive sites where machinery becomes uneconomic.
When harvesting blocks of trees, extraction routes or "racks" need to be planned to allow access at all times.
Felling large hardwood trees is difficult, potentially dangerous and a specialised task. Some of these trees are very valuable and may be ruined if they are not felled properly and split or break when they hit the ground. Even when on the deck, removing the side branches to prepare the main trunk needs great care. Training and supervision are fundamental.
The pattern and sequence of felling and extracting the timber requires careful planning too. Once felled, the side branches and foliage at the top of the tree will need removing and the tree trunk cutting into the required lengths. Sometimes that is done by hand using chainsaws although modern harvesters do this all in one operation using their computer controlled technology.
The timber then needs extracting for stacking at points where timber lorries can come and collect them to take on to the mills for processing into wood products. Extraction is normally done by forwarders - tractors fitted with a loading crane to lift the timber off the ground onto a link trailer or similar system.
Nowadays nearly all timber is stacked mechanically at the roadside using some type of loader, often mounted on the forwarder itself.
Skidders are tractors which extract timber by lifting one end of the load clear of the ground and then pulling the timber length out with the far end dragging along the ground. There are various types of skidders some more suited for certain scenarios than others.
In some cases cablecranes are needed, particularly on steep ground. These are ropeway systems where timber is extracted by means of moving cables, powered by a stationery winch. The timber load is usually carried wholly or partially clear of the ground. Extraction by cablecrane is expensive but may be the only way to extract timber on the most difficult sites.
Chainsaws are still used for harvesting smaller trees in smaller parcels or large valuable hardwoods. Improvements mean that chainsaws are far safer than they once were but they are still potentially very dangerous tools in the wrong hands. It is vital that operators are fully trained, that correct guidelines are adhered to, that all protective clothing is used and that the saws themselves are regularly serviced and sharpened. Training is provided by organisations such as NPTC.
Although they still have a role to play, the use of chainsaws to harvest mature timber is declining in favour of modern machinery