Technodiversity Glossary

The extraction of short logs describes the transportation of the logs from the trail to the forest road (buffer 23 to 33).

It is a mechanized work, usually done by a forwarder or a tractor with a trailer.

For the subprocess of felling there are two options common. The complete tree can be either just felled or felled and then directly hauled.

If the tree is only felled, the subprocess normally is performed motor-manually with a chainsaw. After felling, the full tree remains in the stand (buffer 10 to 11).

If the tree is felled and hauled, the full tree does not stay in the stand after felling but is moved to the trail (buffer 10 to 21), where it will get hauled. These steps (felling and hauling) are executed by a feller and form the second option for the subprocess of felling. The work with the feller is described as mechanized work.

The felling and processing (= harvesting) of short logs can also be executed in one step. Without a buffer to interrupt the process, the complete tree is felled, branches are removed, and the tree is topped and cross-cut.

This process can be done motor-manually with a chainsaw or mechanically with a harvester. If the harvesting takes place motor-manually, the logs remain in the stand near the stump (buffer 10 to 13). If the harvesting is done mechanically, the stem is lifted onto the trail during the process (buffer 10 to 23).

In some cases, the sub-process of pre-skidding is not necessary and can be skipped. Then, the tree lengths are skidded directly from the stand (buffer 12) to the forest road (buffer 32).

This may be the case, if there are no regulations for the machines to stay on a permanent trail or if the technology of the machines makes the sub-process of pre-skidding unnecessary.

Machines which can skid tree lengths directly are for example the cable yarder or the cable skidder. While the cable yarder skids the tree lengths in a carrying movement to the forest road, the cable skidder needs to drag the tree lengths.

The pre-skidding of full trees can be performed either by animals (horse) or as mechanized work by machines.

As machines usually a tractor winch or a cable yarder are taken for the subprocess of pre-skidding.

While the tractor winch and horse can only drag the full tree from the stand (buffer 11) to the trail (buffer 21), the cable yarder is able to carry the full tree to the trail.

During the pre-skidding of short logs, the short logs are moved from the stand onto the trail (buffer 13 to 23). In special cases, the short logs can also be skidded directly from the stand to the forest road (buffer 13 to 33).

Due to the “light” weight of the short logs, there are a lot of options possible for pre-skidding them. They can either be carried manual by a person or a mule or dragged by a horse. Another option is to pre-skid the logs mechanically with a cable skidder.

The cable skidder and horse can also be used for the direct skidding of logs from the stand to the forest road.

The pre-skidding of tree lengths (stem without branches and crown) can be performed either manual by animals (horse) or as mechanized work by machines.

The most common options for the pre-skidding of tree lengths are the use of a horse, tractor winch or cable yarder.

While the tractor winch and horse can only drag the tree length from the stand (buffer 12) to the trail (buffer 22), the cable yarder is able to carry the tree length to the trail (buffer 22).

The skidding of full trees is commonly a mechanized sub-process. For the extraction of full trees several options are available.

The clam-bunk skidder and grapple skidder are normally used only for the skidding from the trail (buffer 21) to the forest road (buffer 31). Whereas the cable yarder and the cable skidder can be taken not only for the skidding but also for the pre-skidding of full trees (buffer 11 to 31).

The transportation of the full tree by cable skidder, grapple skidder or clam-bunk skidder is executed in a dragging movement, the transportation with the cable yarder in a carrying movement.

Cutting tree at the base with chainsaw and fell it in a predefined pattern.

Functiogram:

Advantages

• no need to relocate machines
  
• low investment
  
• accessibility to almost all terrain condition
  
• no need for strip roads (unless needed by extraction vehicles)
  
• no tree size limitation
  
• higher productivity than manual work
  

 Limitations, thresholds

• safety: motor-manual felling is very dangerous
  
• requires high skills
  
• tiresome, high strains
  

Main use

• thinning operations (pure selection)
  
• steep terrain
  
• broadleaf trees with higher dimensions
• wherever machine access is limited

• machine costs without personal costs: 4.00 Euro/h
• personal costs per person: 35.00 Euro/h
• number of persons involved: 1
• in total: 39.00 Euro/h
• regression formula: 
  • b_o = 8
  • b₁ = 15

Ecological suitability:

• Felling damage can occur when the forest stand is dense; depends on the education and skill of the forest worker
• Ecogram 

Social suitability:

• S-class: no work on forest roads -> S5
• E-class: motor-manual work, very heavy and dangerous -> E2

Anonymous (2007): Scope of best operation practice (bop). (unveröffentlicht). Hg. v. Forestry Solutions.

Engler, Benjamin (2011): Gestaltung von Arbeitsprozessen bei der Bewirtschaftung von Eukalyptusplantagen in Süd-China. Analyse gegenwärtiger Arbeitsverfahren und Modellierung eines höheren Mechanisierungsgrades in der Holzernte zur Beurteilung der ökonomischen Auswirkungen. Dissertation. Albert-Ludwigs-Universität Freiburg, Freiburg.

Advantages

• Very flexible, nearly every tree can be processed
• No dependency on skid roads
• Low investment cost
• Low relocation cost

• High need for skills with increasing stem volume
• Dangerous work
• Cost with low productivity
• Effort: heavy cardio-vascular workload
• Need to have at least another (or other 2 workers) at the worksite. Cannot work alone (legal obligation in some countries, in some certification schemes, too)

• Standard at sites with tree-length skidding
• Broad-leaved trees, tree volume too high for harvester or stand not accessible for harvester

• machine costs without personal costs: 4.00 Euro/h
  
• personal costs per person: 35.00 Euro/h
  
• number of persons involved: 1
  
• in total: 39.00 Euro/h
• regression formula
• • b₀ = 15
  • b₁  = 15

Ecological suitability:

• Ecogram 

Social suitability:

• S-class: no contact with forest road -> S5
• E-class: motor-manual work, very heavy and dangerous work -> E2