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After years of very scattered hand-logging, large-scale logging
began on the southern Tongass with the introduction of A-frame logging
along the beaches in the 1930's (Heceta Island and other remote
places). Production was stepped up during World War II with cable
logging in an effort to utilize spruce for airplane materials. As
pulp mills developed to stimulate the economy, modern cable logging
began full production in the late 1950's and early 1960's. Areas
of concentrated logging occurred in the Maybeso Valley near Hollis,
and continued onto Thorne Bay, Staney Creek and Ratz Harbor. Updated
logging systems including skyline, helicopter and balloon logging
have followed.
Seventy years of harvesting has combined for a total of about 3%
of the Tongass being converted to a young growth, or second-growth,
condition (+400,000 acres). The remaining forested land is considered
to be old growth. Old growth is defined as ecosytems distinguished
by old trees and related structural attributes. Old growth encompasses
the later stages of forest stand development that typically differ
from earlier stages in a variety of characteristics which may include
larger tree size, higher accumulations of large dead woody material,
multiple canopy layers, different species composition, and different
ecosystem function.
Stand development after clearcutting is well documented and follows
a general pattern. A new cohort, or age class of trees, with thousands
of newly germinated seedlings, as well as existing regeneration
rapidly occupies the site. Residual shrubs and herbaceous plants
respond to the increased light until 8 to 10 years later when the
conifers begin to overtop the shrubs and herbs. Stand species richness
is greatest at this stage of development.
Without management this new age class of trees will develop to
a point where their crowns begin competing for light. This normally
happens about age 15 to 25. At this stage, few new trees are added.
This is called stem exclusion. Understory shrubs
and herbs decline rapidly at this stage, and begin to fade away
by age 35.
Older stand before thinning.
Click on images to enlarge.
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Older stand after thinning.
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Without management the new age class continues to suppress the
understory shrubs and herbs for up to 100 years (stem exclusion
stage of development). Understory plants do not become well developed
again until age 120 to 150 (understory re-initiation).
At the end of the planning horizon under the Forest Plan (ten years
out), of the scheduled suitable timber acres (676,000);
- 14% will be in stem initiation,
- 62% in stem exclusion,
- 11% in understory re-initiation and
- 13% in old-growth (previously harvested areas older than 160
year of age).
A variety of habitat improvement activities have occurred and are
planned in the future. Habitat improvement projects include activities
such as pre-commercial thinning, cutting canopy gaps into young-growth
stands, shrub and deciduous tree plantings, pruning, and seeding
of forage plants. Annual habitat improvement projects are estimated
at 8,000 acres over the entire Tongass.
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