Associated Oregon Loggers, Inc.
2015 Madrona Avenue, Salem, OR
Old Large Trees

By Rex Storm, Certified Forester

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Oregon’s mature and old-growth forests provide unique characteristics and values that have gained public attention—and therefor warrant special focus by professional forest managers surrounding their management. Most forest managers focus on components of older-forest structure, rather than defining specific land areas as “old” or “mature”.

Forest landowners, managers and professional foresters develop forest plans, goals, and management approaches to address a range of different forest age conditions across the forested landscape, including: young-open forests, middle-aged dense forests, mature large-tree forests, and old growth complex forests. Each of these four forest age conditions has their own unique ecological and social values. The overall pattern and distribution of forest age conditions is an important consideration in sustaining a broad range of values from and forest landowner’s property, and in providing for components of older-forest structure as forests change over time.

Misunderstandings and disagreements about the management of old-growth can be reduced by addressing key questions and considerations, including careful attention to local conditions and concerns about how older-forest structure components are maintained over time. Like the management of other forests, the success of older-forest structure management will be greatly enhanced by experience-based, site-specific plans prepared by professional foresters and forest specialists. Forest plans and prescriptions should be carefully prepared by forest professionals who address local site conditions, detailed management objectives, applicable legal mandates and social concerns.

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Older-Forest Structure Components. The components of older-forest structure are typically derived in three general ways in Oregon forest management. Although there are many definitions for older-forest structure and none are exact, we describe older-forest structure as three important types:

  1. Old-growth forest stands: Areas having large snags and down logs; patchiness; multiple canopy layers; various tree sizes & ages; tree decadence; some relatively largest, very old trees.
  2. Mature forest stands: Areas having large-tree structural attributes similar to old-growth forests; but lacking the largest, very old trees and decadence character. Mature forests have many of the habitat characteristics, which are important to the flora and fauna that favor older forests.
  3. Intra-stand older-forest components: Within a larger forestland area, the forested stand includes islands, clumps, corridors, and/or individual trees having large-tree structural attributes similar to old-growth forests. These inclusions of older trees within a younger stand are commonly managed through special tree reserves—such as stream buffer areas (Riparian Management Areas), wildlife trees, downed logs, wetland perimeters, specified resource site protection, reserve trees, retained seed trees, designated leave clumps, and so forth. Intra-stand older components create many of the habitat characteristics, which are important to the flora and fauna that favor older forests—albeit on a smaller tree-scale. The intra-stand contribution trend is increasing significantly—due to Oregon forest policy upgrades since 1990.

Each of the three aforementioned types of older-forest structure contributes a very important old forest component. Each offers many habitat characteristics, which are important to the flora and fauna that favor older forest attributes. The sum of the three types provides an abundant amount of biological diversity and habitat throughout Oregon’s 30 million acres of forestlands.

Old trees image Active Management for Older Structure. A common misperception is that actively managing older-forest structure is inappropriate or incompatible with other values such as timber production. These misperceptions result in misguided proposals to set-aside mature or old-growth forests, and needless management prohibitions. However, even where non-timber values are primary, active harvesting management of mature and old-growth forests may be necessary to promote or sustain the desired ecological values over time. This is especially true of forests in dry fire-prone landscapes. Older-forest structure management may include an array of professionally prescribed treatments, including thinning trees, burning, patch regeneration harvests, salvaging, and planting.

Forest Professionals Design Structure. Ultimately, concerning older-forest structure, the forest professionals (forester, silviculturist, land manager) are the most qualified individuals to evaluate and prepare forest plans and prescriptions, which carefully address local site conditions, detailed management objectives, applicable legal mandates and social concerns. A “one-size-fits-all” management approach to every older-forest structure situation will not address the range of unique and dynamic forest conditions that occur on a forest ownership. Rather, locally-tailored site-specific plans will more effectively achieve and maintain older-forest structure characteristics. These plans should carefully consider local ecological conditions and objectives, social concerns, and policy constraints of the owners or managers.

Old trees image Considerations to Sustain Older-Forest Structure. The following considerations illuminate the realities addressed by Oregon forest professionals when evaluating older-forest structure:

  • There are three important Oregon forest age-classes: 1) young, open forests; 2) middle-aged dense forests; and 3) older complex forests (mature & old growth). When considering nature and the environment, maintaining a portion of forest area within each of these three ages would be ecologically desirable. Components of older-forest structure can be maintained in each class.
  • There is no optimum single, simple solution to for the complex situation of older-forest structure. Older-forest structure is best addressed on a site-specific basis, including: 1) project needs, objectives & definitions; 2) forest plan goals & values; and 3) policy constraints & rules.
  • One-size-fits-all policy directives or prohibitions, which would dictate specific tree diameter (e.g., 21 inches) or age limits (e.g., 80 years), to accomplish older-forest structure—are patently counter-productive. These approaches strip forest professionals of their local expertise and capability to best provide older-forest structure most effectively.
  • Older-forest structure can be achieved in different sized areas. The area or size of older structure is locally-determined through forest plans and project prescriptions—so that local objectives can be appropriately weighed.
  • Large trees are valuable for many functions, not the least of which is timber value, or habitat value, or aesthetic value. Forest managers consider these values.
  • Oregon forests are owned by several different categories of ownership types—federal, state, county, industrial, tribal, small private, and so forth. Each tends to have their own unique forest objectives—and each therefor accomplishes older-forest structure in different manners. These differences create diversity of older structures across Oregon’s forested landscape.
  • All public forestlands do not conform to the same objectives regarding older-forest structure (national forest, BLM, state forest, county, tribal, local, USFWS). Again, their differences create diversity of older structures across Oregon’s forested landscape.
  • Older forests are constantly changing, growing, dying, and subject to natural destructive disturbances. Older forests are not naturally self-sustaining in a static state. To sustain older-forest structures in Oregon’s forest for the long-term will demand active management, guided by forest professionals.
  • Not all forests had or would ever be capable of achieving old growth conditions. Some forest types fail to or rarely would naturally become old growth.
  • In recent decades, the greatest loss of older-forest structures from Oregon forests has been due to natural disturbances—wildfires, pests, storms, disease, and floods (not from timber harvest).
  • Oregon forest professionals are qualified to grow, manage and enhance older-forest structures over the long-term, through applied science and experience-proven harvest, thinning and regeneration practices that emulate natural disturbances—“active forest management.”
  • Without the legal authority and policy mandate to conduct “active forest management” that addresses older-forest structures, and is implemented by Oregon forest professionals, over the long-term older-forest structures will gradually disappear from Oregon forestlands. No action concerning harvests to maintain older-forest structures will result in continued declines in older-forest structure.