|
Timber Harvesting
This page will provide an introduction to,
and an overview of, the most common types of timber harvesting
operations. Most of the information and photos that you will
find on this website relate to timber harvesting in the North
Western United States. The process of timber harvesting is
carried out in a number of steps, starting with the felling
of the trees and finishing with trucking the logs to the mill.
For this process, a number of different forest harvesting
machines are typically combined to form a harvesting system.
With careful harvest planning, it is possible to select the
best harvest system that will be cost effective and safe for
any given site.
Harvest Planning
There are two stages of harvest planning
- preliminary pre-harvest planning and comprehensive harvest
planning. A pre-harvest plan is a fairly simple plan commonly
prepared by a "service" forester or forestry consultant
for a forest landowner prior to conducting a timber sale.
It normally identifies recommended streamside management zones
as well as potential problem areas like fragile soils or steep
slopes that may require special treatment during the harvesting
operation. A comprehensive harvest plan is much more complex
and detailed. It is usually prepared by the logger or logging
manager just prior to beginning the harvesting operation.
The logging plan may include recommendations on logging roads,
log decks, streamside management zones, stream crossings,
skid trails, and the schedule of activities. The logging planner
must have the following information at his disposal:
The type of cut (clearcut, row thinning, individual tree
selection, etc.). Will trees be removed from the streamside
management zones? This could affect deck size and location,
equipment restrictions or job layout.
The terms of the timber sale contract. For example, the length
of time on the contract may dictate the time of year that
the tract will be logged, which may impact the haul road construction
standards.
The tract topography. In the mountains, topography will often
limit the logger's options for road and deck location. In
addition to slope, aspect and exposure should also be considered.
The tract soil conditions. Soils will affect road and deck
location, Soils also impact equipment decisions and scheduling
of activities.
The tract hydrology. Knowing how much water to expect in
a stream after a big rain will affect decisions on stream
crossing structures.
The tract boundaries, easements, and rights-of-way. This
information is necessary to locate access points and haul
roads.
The timber volumes to be removed by species and product,
and the distribution of those volumes across the tract. This
information is vital for determining haul road standards,
deck size and location, and scheduling.
The logging system and equipment spread. The planner must
be intimately familiar with the characteristics of the logging
operation, including any equipment limitations or operating
constraints. For example, the type of log truck (tandem or
tractor/trailer) will impact the haul road layout, acceptable
curve radius, and landing size.
The applicable laws and regulations affecting logging, including
the current non-regulatory BMP's. These will affect all aspects
of the harvest plan. There are several tools available to
the harvest planner. Topographic maps, available from the
U.S. Geological Survey, are a must in the mountain regions.
In the mountains, every logging planner needs an instrument
to determine percent slope by degree of accuracy. An accurate
estimate of slope is necessary to maintain acceptable road
grade, determine spacing between required water-bars, and
comply with various BMP recommendations. Plastic flagging
of various colors is an important tool for the logging planner.
Boundaries, log deck locations, "back-lines" for
skidding zones, streamside management zones, and designated
skid trails can all be effectively marked and distinguished
by flagging of different colors.
Perhaps the most important tools available to the harvest
planner are his legs and eyes, to be used in a thorough, on-the-ground
reconnaissance of the tract to be harvested. This "walk-through"
will often uncover important features that maps, no matter
how accurate, will not show.
Harvest Methods: Most commonly used.
--------------------------------------------------------------------------------
Conventional ground-based system (flat to moderate terrain)
--------------------------------------------------------------------------------
Mechanized ground-based system (flat to moderate terrain)
-
--------------------------------------------------------------------------------
Cut-to-length system (flat to moderate terrain)
--------------------------------------------------------------------------------
Cable logging /Yarder (steep terrain)
--------------------------------------------------------------------------------
Helicopter logging (steep terrain)
--------------------------------------------------------------------------------
Harvesting Process: The process of getting the trees from
the ‘stump to mill’ can be broken down into 5
steps.
--------------------------------------------------------------------------------
Felling - Severing the tree from the stump and bringing it
to the ground.
--------------------------------------------------------------------------------
Extraction - Pulling the tree from the forest area (or ‘stump’)
to a landing or roadside.
--------------------------------------------------------------------------------
Processing - Delimbing and topping the tree, and then cutting
the stem into logs (‘bucking’).
--------------------------------------------------------------------------------
Loading - Sort, stack and then load out onto logging trucks.
--------------------------------------------------------------------------------
Trucking - Deliver the logs from the landing to the mill for
processing.
|
