Old Large Trees
By Rex Storm, Certified Forester
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
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.
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:
- 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.
- 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.
- 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
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.
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.
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
- 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
- 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
- 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.