In a Buffer Zone
Every Tree Has a Purpose
Two Approaches for Protecting Fish and Wildlife Habitat in Managed Forests
A key element of the Forests & Fish Law is to provide for fish
habitat by protecting cool, clean water in the managed forest by
leaving buffers of trees along fish
bearing streams. Forests are complex and dynamic environments.
Variations in topography, soil type, stream size and other conditions
affect the number of trees foresters are required to leave in the
riparian area. The law requires leaving
the riparian area in a condition today that will grow to replicate
natural stands of older forest at age 140 years. A certain number of
trees and canopy cover need to be left within the riparian zone to
Desired Future Condition (DFC). Both of
the proposed buffer options depicted below will attain the DFC and either
can be used depending upon site specific conditions. Both have a 50-foot
core no harvest zone. Option 1 calls for thinning to encourage growing
large trees faster. Option 2 leaves more trees closer to the stream.
download image (pdf)
Simplifying Buffers Will Improve Monitoring
This option is intended to simplify implementation and monitoring of
the Forests & Fish law. Therefore, two fixed zones replace ten
different buffer widths required under current regulations.
No Harvest Zone Protects Fish Habitat
This option has a 50-foot core no harvest zone and a 50-foot inner
zone. Both zones provide shade to keep
water cool, and large woody debris from
fallen trees to create resting pools for fish, and filter sediment to
keep water clean.
Larger Trees Grow Quicker
The inner zone allows some trees to be harvested depending on the
number and size of trees within the zone. This approach will ensure
that the trees left in the inner zone will grow bigger and faster
while meeting the desired future conditions.
Leave Trees Closest to Water
Sophisticated Modeling Required
This option continues to use multiple buffer widths to reach Desired
Future Conditions. Sophisticated modeling techniques calculate a
harvest plan to establish a buffer width based on the current number
and size of trees today.
No Harvest Zone Protects Fish Habitat
This option has a 50-foot core no harvest zone which provides shade to
keep the stream’s water cool and large woody debris from fallen trees
to create resting pools for fish, and filter sediment to keep water
Harvesting Requires Complex Calculations
The buffer zone widths in this option vary depending on the size of
the stream and site class, which is determined by the productivity of
the soil. The inner zone ranges from 11 to 84 feet. Part of the inner
zone is also a no harvest zone, and is calculated by a model
maintained by the Department of Natural Resources. The portion of the
inner zone where harvest is allowed must maintain at least 20 trees
Trees Grow Quickly to Enhance Habitat
The outer zone ranges between 22 and 66 feet and also must maintain
20 trees per acre. The 20 trees per acre in both zones will grow
quickly in the open and will provide large woody debris in the future.
More About Buffer Zones
The State Forest Practices Rules specifically require that before a
landowner can harvest trees near streams, there be enough trees left in
the riparian area to protect fish and wildlife habitat. This requires
careful analysis and planning. One of the key elements of the Forests
& Fish Law is adaptive management, which is the process of gathering
and using scientific research to evaluate forest management decisions
and practices. The latest science suggests a change needs to be made to
meet the Desired Future Conditions target. The State Forest Practices
Board is considering changing the regulations. As a
result of this change, fewer fish bearing streams across the state will
have harvesting occurring in buffer zones.
The area outside the buffer zones is quickly reforested by planting
trees. The buffer zones on fish bearing streams also provide habitat for
animals other than fish, while the harvested area provides foraging
habitat for many different species. Additional trees must be left
throughout the new rotation of trees to provide perches for birds today,
and additional structural complexity for the stand in the future.
Streams are complex ecosystems that can be influenced by a wide range of
factors. Elements of a healthy stream include pools and riffles, woody
debris, and canopy cover. Pools in small streams provide cool water for
fish to live in during the dryer summer periods. Riffles are important
during salmon spawning since they provide oxygen to hatching fish as
they emerge. Woody debris helps form pools and riffles, as well as
provide cover from predators. Canopy primarily functions as shade to
keep water cool, however, it also can be important habitat for insects
that are a food source for fish.
Buffers – The trees or forest adjacent to an area
requiring attention or protection. For example, areas along streams
that are managed to protect and support fish habitat.
Desired Future Conditions (DFC) – Refers to the
condition of a forest at 140 years, with respect to age of trees,
canopy cover, downed logs, etc. The goal of the Forests & Fish
riparian management strategy is to leave the riparian area in a
condition today that is on a trajectory to replicate the conditions of
natural stands of old forest at age 140.
Large Woody Debris – Pieces of wood larger than 10 feet
long and 6 inches in diameter, which have fallen into, or been placed in
streams to create cool water, cover, and resting pools for fish.
When trees left in buffer zones fall over into streams, they become large
Riparian – The area of land adjacent to and pertaining
to the banks of streams, rivers or other water bodies.
Shade – Trees in buffer zones provide shade that cools
the water. Cool water is critical for nearly all of the fish species
in Washington’s streams.
Snags – Snags are standing dead trees that provide
habitat for many insects and animals. Snags eventually fall in pieces
and become large woody debris on the forest floor or in streams.