Appendix C - [Part
2]
Best Management Practices
(first section)
Timber Production Capability Classification
Fragile Code Guidance
(second
section)
The Timber Production Capability Classification
inventory is designed to identify sites capable of
sustaining intensive timber management without
degradation of their productive capacity. Factors such as
soil depth, available moisture, slope, drainage, and
stability are evaluated to determine the degree of timber
management activity on a particular site. This would
include sites capable of sustaining standard timber
harvest practices, special practices or limitations to
prevent degradation, and sites too fragile to tolerate
any timber management without long-term loss of
productivity. Legislative requirements and BLM policy
specify that timber harvests will be planned and carried
out only on lands which can be managed without
environmental degradation of the site.
A complete description of the system can be found in
BLM State Office Handbook 5251-1, Timber Production
Capability Classification. This is available at the
district office.
This section describes the fragile codes used in the
Timber Production Capability Classification, identifies
the concerns associated with each code, and recommends
potential practices for management of such areas.
Timber Production Capability Classification
Fragile Codes/Guidance
Fragile Nonsuitable Woodland Soil Moisture (FSNW)
Soils on these sites are excessively well drained.
Soils have a very low available water holding capacity
and are subject to being dry for long periods during
spring and summer months. Vegetation communities are
primarily uneven-aged, open-grown Douglas-fir with a low
vigor ground cover of salal. Soils typically have sandy
or gravelly textures with coarse fragments consisting of
more that 70 percent of the top 12 inches of the soil.
Available water holding capacity is generally between 0.5
and 1 inch.
Concerns
Because of the limited soil resource, survival of
newly planted vegetation is low. Any site disturbance
severely reduces the future productivity potential. These
losses cannot be mitigated even using best management
practices.
Recommended Practices
Manage for nontimber uses.
Fragile Suitable Restricted Soil Moisture (FSR1)
Sites with thin light-colored topsoils and coarse,
sandy or gravelly, often shallow soils with low moisture
storage capacity. Available water holding capacity in the
top 12 inches ranges from 1 to 1.5 inches.
Concerns
Because of low moisture supplying capacity and thin
topsoil, soil displacement or compaction significantly
impacts the growth of biomass. Soil compaction or
displacement further reduces the soil's ability to absorb
and store moisture, reducing survival and growth of
conifer seedlings.
Recommended Practices
- Avoid ground-based logging equipment.
- Avoid wet season yarding except with suspension
of logs.
- Avoid scarification or tilling of soil.
- Avoid tractor-constructed fire trails.
- Burn slash only when fire intensity will be low
(see burning guidelines).
Fragile Suitable Restricted Compaction (FSR2)
More than 12 percent of the area is compacted or the
area was scarified and a high percentage of the topsoil
is compacted and/or displaced.
Concerns
Soil compaction and displacement causes reduced
survival and growth of planted conifers. Increased runoff
and erosion may be occurring from the compacted surfaces.
Recommended Practices
- Till with properly designed winged subsoiler.
- Add organic matter to surfaces of displaced soil
to improve productive potential.
- Where sites have been completely cleared of
debris and topsoil, replace topsoil by dragging
and respreading topsoil from piles or
concentrations.
- Drain low spots or blocked drainages to improve
natural drainage.
- Use nitrogen-fixing plants to enhance nutrient
levels on severely disturbed sites.
Fragile Nonsuitable Woodland Nutrient (FNNW)
Soils on these sites are low in nutrients or have a
nutrient imbalance that inhibits tree growth. Soils on
this site are very gravelly or shallow, generally mapped
with FSNW, or already produce less than 20 cubic feet per
acre per year.
Concerns
Forest management activities reduce site productivity
below the threshold level for commercial forest (20 cubic
feet per acre per year).
Recommended Practice
Manage for nontimber uses.
Fragile Suitable Restricted Nutrient (FNR1)
Soils on this site are typically well to excessively
drained. They occur primarily on ridges and ridge noses
or steep (greater than 70 percent) convex hillslopes, at
elevations typically above 2,800 feet (Salem District).
Parent material is frequently volcanic tuff or breccia,
and high in ash. Soils typically have thin topsoils.
Organic matter turnover rates are slow and a high
proportion of site nutrients is stored in the above
ground biomass. Associated vegetation consists of
primarily Pacific silver fir and noble fir with
associated cold-tolerant understory species such as
rhododendron and beargrass.
Concerns
The highest demand for plant nutrients occurs during
the first 15 to 20 years after a plantation is
established. Removal of nitrogen on sites already below
optimum levels for growth would have an immediate impact
on new plantations. While soil nutrients can be replaced
after 80 to 100 years through natural precipitation,
nutrients in deficient soils will not be available in
sufficient quantities during the period of maximum need
by the young stand of trees. Studies indicate that
scarification and burning that cause high biomass removal
on nutrient-deficient soils could have an immediate
detrimental impact on growth.
Recommended Practices
- Avoid burning on these sites when possible.
Usually plant competition is not a factor on low
fertility sites (see burning guidelines).
- Avoid burning on steeper slopes and southerly
aspects.
- Encourage nitrogen-fixing vegetation.
- Use fertilizer to increase nutrient levels.
- Avoid use of ground-based yarding equipment such
as tractors and rubber-tired skidders.
- Avoid scarification and tractor slash piling.
- Plant and thin trees to wider spacings.
- Consider extended rotations.
Fragile Suitable Restricted Nutrient - Impacted
From Past Management (FNR2)
Lower fertility sites impacted by yarding,
scarification, or slash burns, resulting in lowered site
productivity.
Concerns
Site productivity has been significantly reduced by
loss of soil nutrients and organic matter.
Recommended Practices
- Encourage growth of nitrogen-fixing plants.
- Thin trees to wider spacings.
- Use chemical fertilizers to increase soil
nutrients.
Fragile Suitable (very) Restricted Nutrient (FNR3)
Very slow-growing stands of Douglas-fir and hemlock at
higher elevations. Understory includes low vigor
rhododendron and beargrass.
Concerns
Any loss of soil nutrients from logging could shift these
areas into a low site category.
Recommended Practices
- Use practices listed for Timber Production
Capability Classification FNR1.
- Do not burn.
- Do not use ground-based equipment.
- Keep any soils disturbance to a minimum.
Fragile Nonsuitable Woodland Slope Gradient (FGNW)
Slopes greater than 80 percent adjacent to streams and
in headwalls of drainages.
Concerns
Logging or road construction activity is likely to
accelerate surface erosion and/or trigger slides or
debris avalanches into streams.
Recommended Practices
- Manage for uses other than timber production with
a primary emphasis on maintaining water quality.
- Avoid and buffer these sites whenever possible,
especially if there are indicators of
instability.
- If included in timber sale units, fall and yard
away or use full suspension. Buffer the headwalls
or streams.
Fagile Suitable Restricted Slope Gradient (FGR1)
Steep slopes of 70 to 80 percent adjacent to streams
or in headwalls of drainages. Soils are shallow to
moderately deep, noncohesive and gravelly.
Concerns
Logging or road construction may accelerate soil
erosion, ravelling and sliding; may contribute to debris
avalanches. When such materials enter streams, there are
serious impacts to water quality and riparian
(stream-side) vegetation.
Recommended Practices
- Avoid placing roads in headwalls steeper than 70
percent or minimize sidecasting of excess road
construction materials.
- Avoid practices that add water to headwalls or
disrupt the natural drainage.
- Monitor culverts in high hazard areas during high
runoff events.
- Avoid placement of new materials into slide
areas.
- Direct road runoff into ditch lines by insloping
or use of dips.
- Place downspouts on culverts where they discharge
onto steep slopes.
- Yard logs using full suspension.
Fragile Nonsuitable Woodland Mass Movement Potential
(FPNW)
These sites have active deep-seated slump-earthflow
mass movements. Vegetation is primarily alder, bigleaf
mapel, Douglas-fir, and hemlock, with understories of
vigorous swordfern, salmonberry, and other water-tolerant
species. The trunks of many of the trees are commonly
curved and leaning in various directions. Sites include
areas (a) which are unproductive because the soils have
been removed by past sliding, (b) where movement rates
are rapid, precluding even shortened harvest rotations,
or (c) where movement rates are resulting in jack strawed
trees.
Concerns
Management activities could cause accelerated slope
movement and slope failures. Because of the rapid rates
of movement, forest management is not feasible on these
sites.
Recommended Practices
- Avoid disturbance on these areas.
- Avoid unloading bottoms of slides.
- Avoid loading tops of slumps.
- Divert road drainage away from unstable areas.
- Evaluate unstable slopes and design measures to
enhance their stability.
Fragile Suitable Restricted Mass Movement Potential
(FPR1)
These sites occur primarily in undulating topography
containing depressions and sag ponds. Parent material is
primarily sedimentary rock associated with parallel
bedding planes, with sills of diorite, or with tuff and
breccia. Slopes of the slump scarp may be steep but the
average hillslope is on gradients of less than 60
percent. Soils are typically deep and highly productive.
Vegetation varies depending on the depth to a water
table ranging from Douglas-fir and salal to sag ponds
with swordfern, oxalis, devils club, and associated
water-tolerant species. Sites actively moving contain
curved conifer stems and may contain tension cracks and
sag ponds.
Concerns
These sites are subject to slow mass movement. Any
practice that increases weight or soil pore pressure, or
reduces support at the toe, accelerates movement. Runoff
from compacted soil on roads and skid trails that diverts
water into unstable areas is a common cause of increased
instability.
Recommended Practices
- Avoid unloading bottoms of slides.
- Avoid loading tops of slumps.
- Divert road drainage away from unstable areas.
- Maintain or reestablish natural drainage after
harvest operations.
- Evaluate unstable slopes and design measures to
enhance their stability.
Fragile Nonsuitable Woodland Surface Erosion
Potential (FMNW)
Sites that occur on slopes greater than 90 percent not
adjacent to streams or headwalls. The coarse, usually
somewhat shallow soil is moving downslope, accumulating
on the upper sides of trees and other obstacles.
Concerns
The disturbance from timber harvest or slash burning
increases surface erosion to a greater rate. This creates
unacceptable losses in potential productivity.
Recommended Practices
Manage for uses other than timber production with the
primary emphasis on erosion control, watershed and other
nontimber uses.
Fragile Suitable Restricted Surface Erosion Potential
(FMR1)
Sites with steep, convex (upper) sideslopes of 70 to
90 percent. Parent materials are primarily thick-bedded
sandstone, marine basalt, or andesite. Soils typically
have shallow, gravelly, thin topsoils. Vegetation is
primarily drought-tolerant Douglas-fir with an understory
of Oregon grape, salal, and/or rhododendron.
Concerns
Disturbances from logging and slash burning create
increased dry ravelling of soil, losses of soil
nutrients, and covering of newly planted seedlings.
Recommended Practices
- Use full log suspension when feasible. Otherwise,
employ one-end suspension during dry soil
conditions, or use an energized carriage with
lateral yarding capabilities. Minimize the amount
of the area impacted by cable yarding skid
trails.
- Avoid burning to maintain vegetative cover and
the duff layer.
- Leave large cull logs on the unit to help impede
soil movement.
- Encourage nitrogen-fixing plants.
- Consider grass or forb seeding on disturbed areas
where moisture is not a limiting factor.
Fragile Nonsuitable Woodland Ground water (FWNW)
Very poorly drained areas, with water at the surface
for much of the year. Vegetation includes scattered alder
and cottonwood with an understory of salmonberry, skunk
cabbage, sedges or rushes, and devils club.
Concerns
Commercial conifer trees are unable to survive on these
sites except on scattered hummocks or mounds wiht better
drainage. The high water table makes it easily damaged by
timber management or other activities.
Recommended Practices
Manage for uses other than timber production with primary
emphasis on water quality and wildlife.
Fragile Suitable Restricted Ground water (FWR1)
Very moist, poorly drained sites. Usually in
depressions or adjacent to streams or unstable areas
where the water table is near the surface much of the
year. Vegetation is dominated by alder and western
hemlock overstories, and oxalis, vine maple, and
swordfern understories. Salmonberry and devils club are
minor components.
Concerns
These sites may contain water-tolerant species, but
removal of trees could reduce transpiration rates.
Yarding may distupt surface water flows. This can raise
the water table and increase the time in which soils are
wet. This, in turn, could reduce production, increase
competition of unwanted vegetation, and change the
adapted species.
Recommended Practices
- Minimize practices that disrupt natural drainage,
such as dragging logs through wet areas or
leaving skid trails that block natural drainage.
- Avoid use of ground-based logging equipment when
soils are wet.
- Avoid scarification.
- Seed ground cover to reduce invasion of
water-tolerant vegetation.
- Plant species adapted to the site, such as
western hemlock, western redcedar, or alder.
Avoid planting Douglas-fir.
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