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Soil and water resources
Good soil and water quality are basic
requirements for healthy forests. Soil resource indicators
being measured include erosion, compaction and other physical
properties and chemical properties such as levels of organic
Soil erosion is not a major factor
in Oregon, but landslides sometimes occur, whether or not
timber is harvested. Landslides are most common on steeper
slopes, during or soon after heavy rainfall. The effect
of forest practices on landslides
is being studied by many scientists.
Soil compaction eliminates the
air spaces in the soil, making it difficult for plants'
roots to grow. Water can't penetrate soil as easily, which
can increase erosion. Compaction can be caused by logging
equipment, grazing, and vehicle travel. Fortunately, these
processes affect only small areas of the forest. Modern
practices like cable
logging help to minimize the role of timber harvest
in soil compaction.
Organic matter from decomposing
plants improves soil structure, increases water retention,
helps organisms that live in the soil, and stores carbon.
Forests in western Oregon generally have a higher level
of organic matter than forests in eastern Oregon. Many disturbances
caused by humans can reduce the amount of organic matter
in soil. Timber harvest practices have changed in many ways
since the 1970s, to minimize soil disturbance.
Water resource indicators being measured
include: stream flow and timing, biological diversity, pH
(alkalinity vs. acidity), dissolved oxygen, sedimentation,
in stream flow and timing can damage aquatic organisms
and their habitat. Because stream flow is naturally quite
variable, it is difficult to measure the affect of human
activities. There is some evidence that timber harvesting
can increase stream flow in small watersheds,
especially during the fall. During flood events, this effect
is negligible, because the ground becomes saturated whether
or not logging has occurred.
Aquatic organisms. Plants and
animals living in rivers and lakes require good quality
water. If some of them disappear, that could mean that water
quality has gotten worse. At this point, scientists don't
have enough data to know whether aquatic organisms are becoming
less diverse. Studies are focusing on algae, fish and invertebrates
like caddisfly larvae.
Other indicators. Generally,
water quality in Oregon is good in forest streams. One area
of concern is water temperature in lowland areas where development
and non-forest use is common. When streamside vegetation
is removed, more sunlight can penetrate the water, raising
Map courtesy of Oregon
Department of Forestry
Oregon's Forest Practice rules require
no-cut buffers along fish-bearing streams to increase shade
and prevent an increase in water temperature.