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Land and Watershed Management Program
   
Pacific Northwest Research Station
   
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United States Department of Agriculture Forest Service.

Genetic and Silvicultural Foundations for Management

Take a Virtual Trail to learn more about Variable Density Management

Examples of Variable Density Management
From the Pacific Northwest

A silvicultural treatment is designed to influence species composition, spatial pattern, and growth rates so the future stand or landscape condition will meet management objectives.

Uniform stand, Clearwater Study

Clearwater plantation

Larger views of photos on this page are available by clicking on the photos.

In the past, most forest stands in the Pacific Northwest were managed primarily for timber production and conifers such as Douglas-fir were favored. In these stands, silvicultural treatments such as planting, juvenile spacing, or commercial thinning were applied uniformly.

Cutting pattern

In addition, the management units or stands were often delineated with straight lines into fairly square or rectangular blocks.

Spotted owl

Oceanspray

Mount St Helens

Alder stand

In recent years, management objectives for some lands have shifted to emphasize values of other wood production, a mix of wood production, and other values, or producing wood or other forest products from species other than the conifers managed in the past.

Layered stand

Understory fern

Iris

Managing stands for wildlife habitat, for recreational or aesthetic values, for watershed enhancement, biodiversity, special forest products, or wood production compatible with one or more of these values requires different silvicultural treatments than were used in the past or the application of old treatments in new ways.

Old trees

Starcut patches

Variable patches

For example, rotations may be longer in some stands, cutting units may be laid out very differently, and management systems such as uneven-aged management are being evaluated.

Patches of silviculture trees

Mixed stand

Understory in gap

Young stands can be spaced to produce gaps, and composition of both trees and other plants can be altered.

Variable density

Prescriptions for large areas can be quite complex with varied openings sizes and variable density thinnings.

Shelterwood

Planting

More than one strata can be created by retaining overstory trees at the time of a regeneration harvest or planting in openings.

Vine maple

Snag

 

Large logs

Prescriptions can also be altered to preserve legacies from the previous stand such as uncommon species, large shrubs, snags or down logs.

Douglas-fir

Some trees in a stand can be released or a portion of a stand can be planted at very wide spacing to produce large diameter trees with long crowns in the future.

Prethinning

Postthinning

These treatments can be combined into many combinations depending on objectives. For example, the stand shown in this model was thinned to create gaps and leave uncut areas, as well as to increase growth on the remaining trees.

Information on possible pitfalls you could encounter in variable density management.

Tips on ways to accomplish variable density management.

To submit your examples of photos, prescription, pitfalls, or tips related to variable density management contact Connie Harrington.


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USDA Forest Service - GenSilv Team
Last Modified: Monday, 16 December 2013 at 14:18:50 CST


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