EIGHTY FIVE ADVERSE EFFECTS OF SALVAGE
LOGGING ON FOREST HEALTH IN THE INSECT DAMAGED FORESTS OF THE BLUE MOUNTAINS
OF EASTERN OREGON
COMPILED BY BARRY CARTER FOR THE BLUE
MOUNTAIN NATIVE FOREST ALLIANCE - MARCH 3, 1992
EFFECTS OF THE REMOVAL OF LARGE DEAD DOWN
WOODY MATERIAL AND REPLACEMENT DEAD DOWN WOODY MATERIAL ON FOREST HEALTH
1. Salvage logging decreases the availability
and future availability of down dead woody material.
Decaying , fallen trees are an important
component of forest ecosystems and essential to East side forest health.
Their presence on the forest floor helps to create and maintain the diversity
of numerous micro habitats necessary to sustain the ancient forest itself.
2. Spiders, ants and other insect predators
eat budworms.
Many insects, which are found only in
dead and dying trees, are also important in supporting predators that keep
the ecosystem in balance. The natural process is that the newly down trees
are first inhabited by bark beetles. These insects inoculate the wood with
fungal spores and/or nitrogen-fixing bacteria.
Later , the log is invaded by various
wood-boring beetles. Carpenter ants enter as the moisture content increases.
These organisms are important both as prey and as predators. One group
of carpenter ants, for example, feeds on the eggs, larvae and pupae of
the western spruce budworm and the Douglas-fir tussock moth.
3. The decaying trees also act as a reservoir
holding water throughout the year, thus making it available during the
dry season.
This moisture is necessary for the survival
of many insects and animals such as the salamander and small mammals. Maser
et al. 1979 reported that 178 vertebrates (14 herptiles. 115 birds and
49 mammals) utilized downed logs in the Blue Mountains of Oregon and Washington.
Brown (1985) found 130 (30% of all) species using downed logs for either
breeding, feeding, or resting in western Oregon and Washington.
4. The persistence of large logs on the
forest floor has special importance in providing wildlife with habitat
continuity over long periods and through major disturbances such and fire
and drought (Franklin et al. 1981).
Logs contribute significantly to the re-establishment
of animal populations by providing pathways along which small mammals con
venture into bare areas. These animals disperse spores of mycosymbionts
and nitrogen-fixing bacteria.
5. "Management practices can drastically
affect abundance and species composition of the small arthropods that regulate
soil microstructure and elemental recycling"(Moldenke).
Clearcutting and burning can reduce total
arthropods in the soil by 90 percent. Arthropod recovery is related to
intensity and extent of the fire: some survive the fire in refuges such
as punky tree trunks and under heavily decayed logs, and highly mobile
species can return quickly from adjacent areas.
6. The large accumulations of dead, organic
matter in an old-growth forest contribute to a closed carbon and nutrient
cycle.
Removal of large amounts of woody material
from the system will create a nutrient deficit.
Forest productivity in the Pacific
Northwest is usually limited by the availability of nitrogen (Maser en
al. 1988). Decaying, fallen trees provide sites for nitrogen-fixing bacteria
to occur. For example, termites are a host to a protozoan which, in turn
is a host to a nitrogen-fixing bacteria. Logs also serve as sinks for energy
and nutrients which are slowly released and utilized by various members
of the forest community.
7. Fallen trees, when oriented parallel
to slope contours, reduce soil erosion by trapping soil that would otherwise
be washed away by rains.
8. The interface between the soil and
the bottom of a fallen tree is one of the richest areas in the forest in
terms of nutrient cycling and exchange (Maser et al. 1989).
9. The most productive habitats for salmonoid
fish are small streams associated with mature and overmature forest where
debris and fallen trees greatly influence the physical and biological characteristics
of the streams (Maser et al. 1988).
Such debris increases habitat diversity
by forming pools, providing nutrients and substrate for biological activity,
dissipating the energy of the flowing water and trapping sediment. Fallen
trees that cross streams also provide migration pathways for insects and
small mammals.
THE EFFECTS OF THE REMOVAL OF LARGE SNAGS
AND REPLACEMENT SNAGS ON FOREST HEALTH.
10. Snags are an important component of
a healthy eco-system.
Large standing snags were once a common
part of the landscape when mature/old-growth stands also were a common
component. "Each forest community supports a distinct combination of primary
excavators and secondary cavity users. Each species has a distinct requirements
in terms of the minimum diameter and height of the snags used for nesting
and shelter. Each forest community has different requirements in terms
of the number, species, and size of snags necessary to support all the
cavity users associated with that community."(Thomas, 1979).
Three biological considerations are
relevant concerning snags: "(1) the same snag can be used by several cavity
excavating species; (2) birds of the same species will not usually excavate
twice in the same snag; and (3) larger snags can be substituted for smaller
snags--the reverse is not true, however." (Thomas, 1979).
Therefore, the once common larger tree
forests with its corresponding larger snags provided a distinct habitat
for associated species. Salvage logging, along with the cumulative impact
of past timber sales surrounding salvage areas, will further reduce the
possible recruitment of large snags.
11. Large diameter snags must be distributed
throughout the forest if the forest is to remain healthy.
Limiting large-diameter snags to riparian
areas, old-growth patches and other areas not salvage logged or managed
for timber production will diminish diversity and impact forest health.
We know that "most . . . hole-nesting birds (are) more abundant in Old-Growth
stands than in managed stands. These species all used snags as nest-sites,
and most, especially woodpeckers, foraged for insects in the bark and wood
of snags. An examination of snags in managed and Old-Growth stands showed
that the proportion used as nest-sites and substrates for foraging generally
increased with the size of the snag. Consequently, the density and proportion
of snags used were greater in old-growth stands than in managed stands.("Bird
Populations and Vegetation Characteristics in Managed and Old-Growth Forests,
Northeastern Oregon", by R. William Mannan and E. Charles Meslow, Journal
of Wildlife Management, 48(4), 1984, p.1228).
"Species of specific concern are the
38 birds and 24 mammals that utilize tree cavities for nesting, shelter,
and roosting. The majority of bird species are insectivorous." (L&RMP
IV-40).
12. Cavity nesting birds help keep tree
damaging insects in check.
With few exceptions the conclusions of
hundreds of papers dealing with the impact of avian predators on their
insect prey have been that, in many instances, birds act as important components
of natural biological regulation of insect population dynamics at endemic
levels. In some rather unusual circumstances birds may act together, each
species and sometimes each sex in its own specialized way, to be a major
cause of the suppression of an insect outbreak. The most important role
of birds is in the prevention of insect epidemics, rather than their suppression."
(Thomas, 1979, p.64).
Salvage logging will continue to diminish
the nesting sites of the insect eating birds by reducing snags and vegetative
layers below those needed for optimum populations. During this time of
high insect numbers, management strategies should maximize avian predators
by preserving and restoring snags and conserving vegetative layers.
As the number of insectivorous birds
is diminished, the impact of forest pests is increased. "There is evidence
that, through the consumption of insects which are destructive to the forest,
these birds may contribute significantly to the prevention or reduction
of insect outbreaks."
"Although the relationships between
insectivorous bird populations and populations of forest-damaging insects
are not fully understood, there is ample evidence to support maintaining
higher than minimum population levels of these species." (L&RMP 2-7).
13. Salvage logging creates forest edges
that increase predation on insect eating birds.
During pre-settlement times disturbance
and edge-loving species were relatively less common than species typical
of a mature forest. Salvage logging reverses this. As the edge-loving species
increase, the predation on the interior forests (mature) species also increases.
Arboreal nests located along edges may be most susceptible to avian predators
as amounts of edge increase in the future with continued forest fragmentation.
14. Pileated woodpeckers eat ants.
In a recent study conducted by Evelyn
Bull (1991) it was found that the overall diet for pileated woodpeckers
was 68% carpenter ants, 29% thatching ants, 0.4% beetles and 2% unknown.
Carpenter ants are present in the diet all year. The change in diet from
thatching ants in the summer to carpenter ants in October probably reflected
availability of the prey. Thatching ants nest in soil or in very decayed
logs. When snow covers logs in winter, the thatching ants are probably
unavailable to the woodpeckers as prey. Carpenter ants also nest in soil
and logs as well as in standing trees (live and dead), so when snow covers
logs, the woodpeckers can prey on these ants in standing trees all winter.
15. Pileateds need standing live and dead
large diameter trees.
According to Evelyn Bull, " Because of
its large size and resultant need for large dead trees for nesting and
dead wood for foraging, the pileated woodpecker seems likely to be impacted
by intensified timber management. Large diameter wood typically becomes
scarce as forest management intensifies and rotation ages decline. To provide
for the continued existence of pileated woodpecker populations, the National
Forests established requirements for pileated woodpecker management areas
containing large amounts of standing and downed dead wood. It is essential
that those areas contain the habitat components critical to their survival."
These 600 acre areas provide for nesting and foraging, however roosting
habitat was not considered.
Habitat requirements of nest trees
have been well documented (preference for large ponderosa pine and larch).
While nest trees are important for rearing of young, roost trees are used
all year.
To provide for roosting habitat Bull
recommends leaving old- growth stands of grand fir with greater than 60%
canopy closure with no logging or high grading. There should be an abundance
(greater than 10 per hectare) of grand fir greater than 50 centimeters
diameter at breast height, live and dead grand fir. Actual roost trees
were an average of 70 centimeters diameter at breast height, live or dead,
and had conks of Indian paint fungus and an old injury if they were grand
fir. Dead western larch and occasionally live larch with extensive decay
are also used as roosts. Any combination of the above variables determines
the recommended number of roost trees. Potential roost trees and appropriate
habitat conditions need to be maintained and managed for. Distribution
should be within four old-growth stands (at least one half kilometer apart)
in each 243 hectare management area at various slope locations. At least
one of these stands should be on the upper third of the slope and should
contain a combination of large-diameter dead ponderosa pine( if pine occurs)
and live or dead grand fir for use in the winter. Roost trees should be
maintained in foraging areas as well as the nesting areas.
"It is essential in the management
of this species to provide habitat for foraging and to provide trees for
both nesting and roosting. If one of these components is missing, a viable
population will not survive." These conditions cannot be maintained in
any heavy salvage logging situation.
16. Pileateds create nesting holes for
other birds that feed on budworms.
Pileated woodpeckers are one of sixteen
primary cavity excavators. Others are black-backed woodpecker, williamson's
sapsucker, white-headed woodpecker, red-breasted nuthatch, whitebreasted
nuthatch, pygmy nuthatch, common flicker, lewis' woodpecker, yellowbellied
sapsucker, hairy woodpecker, downy woodpecker, northern 3-toed, black capped
chickadee, mountain chickadee, chestnut-backed chickadee. ( Wildlife Habitats
in Managed Forests, Jack Ward Thomas, 1979). "If the birds that chisel
out cavities (primary excavators) are provided for, then the cavities they
leave will probably provide nesting sites for secondary nesters." The secondary
cavity nesters are wood duck, common goldeneye, Barrow's goldeneye, bufflehead,
hooded merganser, common merganser, American kestrel, barn owl, screech
owl, flammulated owl, saw-whet owl, vaux's swift, ash-throated flycatcher,
violet green swallow, tree swallow, brown creeper, pygmy owl, and barred
owl, house wren, western bluebird, mountain bluebird, starling, house sparrow.
Mammals include opossum, little brown myotis, long-eared myotis, long-legged
myotis, California myotis, silver-haired bat, big brown bat, pallid bat,
yellow pine chipmunk, western gray squirrel, eastern fox squirrel, red
squirrel, chickadee, northern flying squirrel, deer mouse, busy-tailed
woodrat, raccoon, marten, fisher, short-tailed weasel, long- tailed weasel,
spotted skunk.
17. Mycorrhizal fungi require old growth.
18. Mycorrhizal fungi aid in the nutrient
uptake of trees.
19. Mycorrhizal fungi are spread in the
droppings of voles and other small mammals .
20. Voles are kept in check by small owls.
21. Owls require old growth protection
from larger predators.
FIRE EFFECTS ON FOREST HEALTH AND THEIR
RELATION TO SALVAGE LOGGING.
22. Fire may be a necessary contributor
to healthy soil.
Fire effects in the "below ground" of
the natural forest are little known nor appreciated. Most forest soils,
without the influence of periodic fire, become too acid due to constant
needle accumulation. Periodic fire not only reduces the physical barrier
of this needle mat, thus exposing a mineral seedbed, but also makes the
soil more basic. This encourages a renewal of the bacteria/mycorrhizal
fungi system that is so vital to nutrient availability/uptake by trees.
In the natural system, the mineral seedbed was quickly occupied by various
grasses, forbs and shrubs. Some of the broad leafed plants were nitrogen
fixers and they all were contributors to the Ca and Mg budget of the active
layer. This enhanced the "cation exchange capacity" which directly reflects
nutrient availability to trees.
23. Fire discourages insect and disease
organisms.
Fire in the natural forest affected insect
and disease organisms in a direct and indirect fashion. Heat and smoke
destroyed them or created a condition that was not favorable for their
survival or that favored another organism that simply crowded them out.
An example of "crowding out" would be the sugar fungus which when encouraged
by fire "crowds out" laminated root rot. This was documented by the U.S.
Forest Service's Intermountain Station in one of their publications.
24. An important point to remember is
that fire in the natural forest did not only keep fuels at natural levels,
and control tree spacing/species composition, but played many other critical
roles; many of them "below ground".
25. Timber harvest with alternate fuel
treatments may or may not improve forest health without fire. Certainly
fire will have to occur in these locations at some time in the future.
26. Species composition goals should be
based on pre-settlement conditions.
Species composition targets in our quest
for "forest health" should be those documented by the natural system when
fire played it's necessary role. For example we might expect, in general,
to find mixed conifers on north slopes going heavy to larch, ponderosa
pine, and Douglas fir toward the ridge with pine and larch with some Douglas
fir on ridge tops and going to mostly pine on south slopes. Grand fir and
spruce occupied the cooler and wetter environments; those not so susceptible
to fire, those with a longer "fire interval".
27. Salvage logging encourages the view
that the forest consists only of trees.
In spite of our best intentions, we are
focusing in on the health of forest trees and once again forgetting that
forest health is the reflection of the health of all the parts of a forest
system. We have to deal in a realistic and honest fashion with soils, water,
plants other than trees, animals, insects, microorganisms, fish, and a
host of others. This doesn't even consider the array of complex relationships
among all of these.
28. Ponderosa pine should not be removed
on east side salvage sales until the forest health is restored.
None of the ponderosa pine should be cut
during salvage operations associated with current forest health. Only the
Douglas fir that is severely impacted by insects or disease should be harvested
as should be the case with western larch. Mistletoe damage would be the
major factor considered in decisions concerning salvage of these species.
In the case of Douglas fir, bark beetle impacts may also be an important
indicator of those trees which need harvest.
29. Salvage logging is an excuse to take
large old growth trees
30. Salvage logging should only remove
ladder fuels from the understory
31. Stocking control, whether by fire
or mechanical means, is as important an issue to be dealt with as species
composition.
The natural system carried far fewer stems
per acre of trees than we have tried to impose on the forest. The extensive/intensive
work that Fred Hall has done in the Blue Mountains clearly documents that.
THE EFFECTS OF SALVAGE LOGGING ON SOILS
AND WATER.
32. Timber harvest and its associated
road building can affect watersheds by increasing either the amount of
sediment or the volume of water within a stream channel. If the increase
in either is great enough, equilibrium is upset.
33. Openings increase peak stream flow
in three ways. Water that trees use in the transpiration process becomes
available for stream flow.
34. Snowfall that is normally intercepted
by tree crowns and sublimated (changed from solid to gaseous state) back
into the atmosphere also becomes available for stream flow.
35. The redistribution of blowing snow
into openings makes more snow readily available to the subsequent melt
process.
36. One of the main functions of a watershed
is to dissipate energy.
The energy stored in the water that is
high on the hill side is dissipated by the "pool/riffle" sequence. This
alternating series of shallow and deep areas forms steps along the length
of the channel that allows energy that is gained in the steeper, riffle
areas to be lost in the deeper pools.
The increased peak flow fills the pools
with silt and causes the stream to widen out. This cuts more soil from
the banks filling in the pools farther down and continuing the process.
37. Budworms are more likely to attack
even aged stands that have already been cut over in the past.
These areas are also likely to adjoin
other recently cut areas. The cumulative impact of these openings is more
likely to increase sedimentation.
38. Soil compaction associated with logging
makes it harder for the roots of surviving trees to get water so they cannot
make as much pitch to throw off insects.
39. Now is the time, while we are inventorying
forest health needs, to begin a new information base that is grounded in
soils and their existing condition.
We need to realize the decrease in long
term productivity due to our past management activities on our soils and
adjust our future plans and expectations appropriately.
40. Decrease of condensation drip as a
contributor to the total water regime.
Large trees intersect the air flow over
the forest. When they are cooler than the surrounding air moisture from
the surrounding air condenses on them. Studies done in the Bull Run watershed
near Mount Hood indicate that as much as 30% of the total water input into
a forest ecosystem may be from condensation. While the drier air crossing
east side forests may not contribute as high a percentage to the total
water regime it is expected that it will still be a significant contribution.
East side forests have not had any studies of this effect.
41. Total impacts associated with forest
health prescriptions need to be modeled using what ever method is approved
by the plan covering the public land in question.
The level of activity that puts stream
sedimentation or whatever parameter up against the standard acceptable
should be arrived at and then the actual level implemented on the ground
should be no more than sixty percent of that.
42. Openings change the periodicity of
water
43. Salvage logging removes potassium
from forest soils.
"The potassium cycle (in the soil) is
relatively simple, but this element is not available to plants until it
is converted to water soluble compounds by bacteria, mycorrhizae, and possibly
other organisms....Potassium is lost from forest soils mainly when it is
leached out by erosion and when wood is removed from the land by logging."
(Excellent Forestry, by Gordon Robinson, Island Press (1988), p.80)
44. Salvage logging removes calcium and
magnesium from forest soils.
"Calcium and magnesium are widely distributed
in the earth...and are essential to both plant and animal life but are
available to plants only in soluble compounds....In nature, they are recycled
adequately in most ecosystems. However, in situations in which crops are
removed from the land, their cycle is broken. Unless measures are taken
to minimize losses, and either to limit harvesting to match the natural
rate at which calcium and magnesium can be derived from inert minerals
or to artificially replenish them, the soil will become impoverished over
a period of time."(Ibid., 89)
45. "The rich nutrient reservoir in forest
soils can be lost or depleted in several ways: by removal of the timber
itself during logging;
46. by the compaction caused by the use
of heavy equipment during logging and road construction, which destroys
the microorganisms in the soil and causes the nutrients they contain to
be leached out;
47. by erosion, which transports soil
nutrients out of the water shed;
48. by exposure caused by removing vegetation
that casts shade, retaining a relatively humid atmosphere and preventing
the soil from becoming too hot for survival of microorganisms; and
49. by the practice of tree monoculture,
particularly when herbicides are used to suppress competing vegetation."(Ibid.,
89)
50. "Some foresters have argued that nutrient
cycles should play the determining role in logging. They theorize that
the allowable cut and rotation should be calculated by determining the
rate at which nutrients are replaced naturally, taking into account the
rate at which they are extracted due to logging."(Ibid., 90)
51. "As many as 70 different species have
been collected from less than a square foot of rich forest soil. The total
animal population of the soil and litter together probably approaches 10,000
individuals per square foot."(Ibid., 87)
"Compaction contributes greatly to the
reduction of soil quality by destroying large numbers of microorganisms,
thus permitting the nutrients they normally store in their bodies to be
released into the soil as leachable solutes.
52. In addition, their decreased number
reduces the rate at which insoluble minerals are converted into soluble
substances that plants can use.
53. Compaction also reduces the ability
of the soil to absorb water.
When rain falls or snow melts on compacted
soil, the water runs off instead of soaking into the earth, so compaction
causes erosion as well."(Ibid., 90)
54. Erosion increases as the result of
forest cover removal.
"Research conducted in Japan and reported
in 1971 by Hidenori Nakano revealed that erosion sharply increases in proportion
to the amount of forest cover removed...Erosion increases exponentially
with...a linear increase in runoff, so doubling the runoff results in a
fourfold increase in erosion."(Ibid., 91, 92)
55. Four ways to preserve forest soils.
"We can best preserve forest soils by
forest management practices that (1) keep openings in the forest no larger
than is necessary to satisfy the biological requirements of the tree species
being harvested, so as to satisfy the biological requirements of the tree
species being harvested, so as to encourage natural regeneration; (2) provide
for long rotation, which will supply high-quality timber, because the timber
will be allowed to achieve optimum growth, and minimize disturbance to
the soil; (3) rely on natural controls to protect the forest from insects
and disease, so as not to harm the microorganisms in the soil that carry
much of its nutrient load; and (4) use methods of logging and road building
that prevent the soil from being compacted and keep erosion to a minimum.
Small, lightweight equipment should be used for logging, and roads should
be laid on the land rather than cut into it."(Ibid., 96)
EFFECTS OF ROADING ON FOREST HEALTH.
56. Salvage logging invariably involves
roading.
The average road devours a strip of land
approximately fifty feet wide as it snakes it's way through the forest.
This equates to six acres per mile, or, for example, to fifty-four thousand
acres for the nine thousand miles of road on the Wallowa-Whitman National
Forest.
57. The road prism cuts through and interrupts
the subsurface flow of water which naturally replenished the springs and
streams in the forest.
This water often evaporates and is lost
to the system. A significant decline in health has resulted from this drying
up of the forest.
58. This drying effect is compounded by
the impacts of livestock grazing and mining which are encouraged by the
presence of roads.
59. The increased openings created by
roading and clearing resulting from salvage logging present a greater chance
of incursion by domestic livestock.
Livestock trample the springs until they
cease to flow. They compact the soil which interferes with percolation.
They take all the vegetation from the slopes and riparian areas so that
peak flows are increased dramatically and late flows are reduced to very
low levels. The results of all this is that the stream beds scour out until
they are six or eight feet deep (or more) taking the water table with them.
Mining results in many of the same impacts as domestic livestock but in
a much more direct and dramatic fashion.
60. Roads are the major culprit when it
comes to introduced sediment, accounting for 80 to 90% of the accelerated
load.
Sediment is most often introduced into
streams during and immediately after the construction process, when the
most ground is disturbed. However, this sediment is often small enough
in size and amount to be carried away by the existing stream flow. As a
result, it is rarely noticed. It is usually deposited in areas of lower
gradient such as spawning gravels and pools.
61. More catastrophically, sediment is
introduced into streams by mass-failures.
These most often occur after road construction
is complete, when precipitation events, altered by roads, can overload
sections of hillsides with water and cause landslides.
62. Even stable non sediment producing
roads, play a part in exacerbating the effects increased water yields.
Watersheds with high road densities have
had what amounts to an additional drainage system superimposed on their
slopes. This ability to move water to the channel faster increases the
likelihood that increased peak flows will be the result of harvest induced
water yield increases.
63. We need to commit ourselves to a reduction
in access as a part of this program.
No new roads or skid trails, line trails
included, and putting to bed most of the old system that is re-used for
this program should be the commitment.
64. Past management practices, such as
over roading, in conjunction with recent weather patterns have given us
a much drier patient to work with than the natural system had when the
forests we are now enjoying were born.
An awareness of the current status of
the patient as compared to that when they were healthy is an important
part of any good health program.
65. Entry into some salvage areas is an
excuse for roading
66. Roading creates barriers to the movement
of some desirable old growth species and facilitates the movement of undesirable
non-native species (i.e. humans).
According to Reed Noss road building creates
barriers to dispersal of flightless beetles and other insects. A network
of roads fragments populations into smaller units and makes them more vulnerable.
Reed Noss also said road density is the number one threat to animal diversity.
This is partly because of road kills and increased hunter access. This
effects bears and wolves especially.
67. Effects of roading on hiding cover:
"Dissecting a forest with roads (a) "may diminish its value as wildlife
habitat."
68. "Roads exacerbate the problem of forest
fragmentation." (Oxley 1974, Maser 1984, Small & Hunter 1988)
69. "Roads open to the public may facilitate
over hunting and disturbance in general." (Malcomb Hunter Jr., 1990)
70. Under no circumstances should any
un-roaded old growth areas be roaded and logged
THE EFFECTS OF CREATED OPENINGS ON FOREST
HEALTH.
71. Created openings such as salvage clear
cuts and roads change the patterns of wind movement.
Trees near the edges of created openings
are particularly at risk of windthrow since they have matured within a
closed canopy and have therefore developed in the absence of strong winds
and lack the necessary support mechanisms to deal with such winds.
72. Seed trees, shelter wood, snags and
replacement snags are also at high risk of windthrow for the same reasons.
73. Increased wind penetration into the
uncut fragment areas also increases evapotranspiration with reduced humidity
and increased desiccation.
74. In cleared areas, in general daytime
temperatures are higher and night temperatures lower than in naturally
vegetated areas. This leads to greater temperature ranges both at the surface
and in the upper layers of the soil, and an increased incidence of frost.
75. Elevated springtime temperatures on
trunks at the forest edge allow larvae to emerge before their parasites,
which emerge from the cooler forest floor. This gives the pest a head start
and results in population buildups.
76. Increased wind speeds at remnant edges
have the secondary effect of increasing the transfer of material such as
dust and seeds in from the surrounding areas.
Transfer of nutrients is also possible.
Strong gradients in soil nutrient levels have been found at the edges of
remnant areas.
77. Transfer of insects and disease organisms
into remnant areas may also be increased.
THE EFFECTS OF SALVAGE LOGGING ON OTHER
BIOLOGICAL FACTORS.
78. Increased openings increase possible
impacts of cattle.
79. Only 10% of Pacific Northwest old
growth remains. This may not be an adequate genetic pool.
80. The fragmentation of OG stands leads
to the isolation and interbreeding of genetic stock
As the population is reduced in size the
frequency of inbreeding due to chance will increase. "Inbred populations
have less potential for adaptation to environmental changes. The consequences
of inbreeding observed in individuals can be placed into four categories:
fetal survivorship, neonatal and juvenile survivorship, competitive ability,
and adult fertility and fecundity." (Harris, 1984).
81. Increased sunlight on sensitive species.
82. Adult plants are often less sensitive
to changed environmental conditions than seedling and juvenile stages.
This is an increasingly important factor as we move into global climate
changes brought on by ozone depletion and global warming.
83. Opening up large areas of the forest
increases the impact of ozone depletion related UV and could be a factor
increasing the frequency of cataracts and other adverse effects in shade
loving species.
84. In one area that has been mentioned
as hardest hit by the budworm there was only 15% mortality. The trees that
survive are likely to be more resistant to future infestations.
85. Herbicides, which are often used after
salvage logging, destroy early successional nitrogen-fixing shrubs, interfering
with the natural recovery process of a stand and reducing site productivity.
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