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Tree
and Forest Restoration - Pros
and cons of salvage logging in perspective
Burned areas,
particularly those with severe fire effects must be considered “ecologically
sensitive', especially during the first several years following
the fire. Water is the greatest source of soil erosion in Inland
Northwest forests—therefore, the benefits of increased infiltration
rates due to soil disturbance must be weighed against the potential
of greater soil erosion. Logging activities immediately after a
fire event have the greatest beneficial potential since this is
also when water infiltration rates are lowest and erosion rates
the highest. This is also when seed-bed modification may enhance
recovery rates of desirable native plants. Logging during the growing
season six months following fires may have the greatest detrimental
effects by disrupting plant recolonization.
In the spring
and summer following a fire, specific native “colonizer”
species such as fireweed have been shown to rapidly invade severely
burned areas. Surveys of lower elevation sites that burned in the
Bitterroot during 2000 have shown that fireweed provides approximately
50 percent surface cover, helping to stabilize soils. Logging during
the growing season on such sites can have significant detrimental
soil effects, as the stabilization associated with such early successional
plants will be disrupted. Logging on a snowpack or frozen ground
in the years following a wildfire may alleviate some of these negative
effects.
Although noxious
weeds may be vectored by logging activities, proper treatment of
equipment prior to transport into burned areas can be very effective
at reducing this risk. Many members of the Montana. Logging
Association have partici- pated in weed workshops where such practices
are taught. Other factors such as human use (mushroom picking for
example), wildlife and existing weed sources must also be taken
into consideration.
Shading effects of dead
standing snags and logging debris should theoretically increase
colonization rates of native plant species and tree seedlings. Which
has the greater effect is often debated. The com- monly accepted
average temperature lethal to plants is 125° F (55° C) for
one minute. Since measured surface temperatures are commonly above
150° F on burned sites, beneficial effects of shade created
by materials more than three feet above the soil surface is minimized
due to the rapid movement of that shade with the sun. Logs that
are horizontal across the soil surface will have a greater shade
effect for the creation of microsites. This may be a positive aspect
of salvage logging if logging debris is properly distributed.
Research indicates that
roughly 90 percent of the nutrients incorporated by tree biomass
are located in small diameter structures such as twigs and needles.
Salvage logging removes larger diameter bole wood that is suitable
for lumber production and leaves the finer materials. The role of
larger diameter woody debris in soil development has also been recognized
as important, and therefore, should be taken in consider- ation.
Typically, logging results in a significant number of large diameter
logs with too much defect for mills. Proper distribution of these
materials across the landscape should be an important component
of good slash management.
Woody organic matter
becomes an important soil component when it has reached advanced
stages of decompo- sition and is capable of retaining large quantities
of moisture. At this point it is also a lesser contributor towards
wildfire risk. In contrast, dry intact logs represent a considerable
risk for severe fire effects. In any fire-prone ecosystem, the potential
soil benefit from decomposed organic debris is offset by the high
fire risk period while organic debris is decomposing. Depending
on the forest type, a log may require between 20 and 200 years to
reach an advanced stage of decom- position. During this time, the
site is at risk of soil degradation from a severe fire. The higher
the organic debris component, the higher the potential soil benefits
but also the higher the risk of losing it all from fire.
There is substantial
evidence that standing dead or dying trees resulting from wildfires
do provide habitat for a variety of wildlife. Most of the species
involved are categorized as fire “opportunists” that
benefit from fires but are not dependant on the effects of wildfires.
Nonetheless, leaving fire damaged/killed trees for wildlife habitat
is an important consideration. In attempt to provide for this need,
many salvage logging protocols call for certain numbers of large
diameter leave trees per unit area. While this may be helpful for
some species, other research indicates that wildlife such as Black-backed
woodpeckers require dense stands of fire-affected trees. Therefore,
leaving patches of fire killed trees along with other areas that
have widely distrib- uted snags may be the best approach. Much additional
research is needed to answer questions of how much, in what distribution,
and what species of trees are needed.
Based on this brief
summary of the issues surrounding salvage logging, it is apparent
that there are potential ecological benefits from salvage logging
and potential ecological detriments. The ecological side of the
question: “Should salvage logging occur?” is really
one that revolves around the magnitude of the fire effects. Removal
of all trees killed by fire will have a potentially negative impact
on wildlife and may reduce soil productivity in the long term. Removal
of some of the trees coupled with sound slash management has the
potential of decreasing soil surface erosion, decreasing future
risk of severe wildfire effects and increasing recovery rates of
desirable vegetation. No manipulation of severely burned areas will
result in soil erosion risks, future severe wildfire risks and conversely,
a large pool of organic matter for wildlife use and future soil
amendments. The larger the area affected by fire, the greater the
possibil- ity of creating a mosaic of salvage and no-salvage logged
areas that could enhance the benefits from both.
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