Washington Forest Protection Association

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 achieve this 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.

Graphic Depicting Two Approaches to Achieve Desired Future Conditions in Buffer Zones

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Commercial Thinning

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 clean.

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 per acre.

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

Adaptive Management

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. Learn More

Harvest Areas

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. Learn More

Stream Beds

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. Learn More

Key Terms

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. Learn More

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 woody debris. Learn More

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.