Biodiversity Management in Forestry and Silviculture Programs
This carefully managed forest stand at the
U.S. Air Force Academy demonstrates many
qualities of biodiversity conservation, such
as structural diversity and good understory
management. (Photo: Douglas Ripley)
Managing forest biodiversity at an installation requires consideration of landscape
elements of scale, disturbance, fragmentation, and habitat. At the local
level, forest stand attributes such as structural diversity, crown closure, fuel loads,
soils, standing dead trees, coarse woody debris, tree species diversity, and large
wildlife trees, have a direct impact on biodiversity. When considering the various
forest elements critical to biodiversity, it is also essential to consider the interaction
of forests with other habitats, and the interdependence of habitats (e.g. unimproved
grassland, wetlands, and hedgerows).
Regardless of size, forests can provide habitats for a range of flora and fauna.
Even small, recently established forests within otherwise intensively cultivated
land can be useful, although the scope may be limited due to isolation and, in certain
circumstances, they can harbor pest species. Forest management scales are
generally defined by human-made or jurisdictional boundaries (e.g., landscape
unit, watershed, forest stand) and on military installations by mission-related requirements.
They do not necessarily apply to biological systems and managers
may need to adapt them to accommodate more biologically sound scales. This
may require coordination with local and regional neighbors.
Natural disturbances are important to biodiversity and help shape plant and
animal communities. For example, areas with high fire frequency have more earlysuccessional
taxa than areas with longer intervals between fires (Bunnell 1995).
The degree to which species have co-evolved with and are dependent on natural
disturbances varies with the species. However, at some scale, all species require
natural disturbances for persistence (Bunnell 1995).4
Disturbances due to forestry practices have different impacts on biodiversity
than natural disturbances. Natural disturbances interact with the geology, climate and vegetation, and result in a complex mosaic of habitats at the landscape
scale, while conventional logging, such as clearcutting, tends to homogenize the
landscape. This can be compensated to some degree by creating snags, leaving
standing and downed dead wood, and using other means to create a mosaic of
Air Force Forester Kevin Porteck conducting
a timber inventory at Andrews AFB, Maryland.
Professional military foresters play a
critical role in ensuring the viability of commercial
forestry programs while simultaneously
supporting the military mission and
biodiversity conservation. (Photo: Douglas
Within the landscape context, fragmentation and habitat loss are two separate
processes (Andrén 1994, With and King 1999). Two areas may have the same
amount of habitat, but the spatial arrangement of remnant habitat and thus the
amount of fragmentation within each, can be drastically different. Fragmentation
of forest habitat into smaller isolated patches reduces the total amount of habitat
area, increases edge effects around habitat patches, reducing the core area,
and increases patch isolation. Current research findings suggest that overall habitat
loss has a much larger effect on biodiversity than the spatial arrangement of
remnant habitat (Fahrig 2001).
Biodiversity management strategies for managed forests should be applied in
the preparation of forestry plans; silviculture prescriptions, and logging and fire
management plans. To maintain or restore biodiversity in managed stands, some
or all of the following attributes should be present:
- Structural diversity is achieved when there is a variety of canopy layers (vertical
structure) and spatial patchiness (horizontal structure). This creates more habitat
and micro-climate diversity than in homogeneous stands. Structural diversity
can be maintained or created through the choice of silvicultural system, harvesting
methods, and stand-tending activities such as tree planting, pruning, fertilization,
and pre-commercial and commercial thinning.
- Soil biodiversity can be achieved by forest soils management and forest practices
that minimize soil disturbance and help maintain the below-ground biodiversity.
Soil structure, nutrient spectrum, organic matter content, water retention,
drainage, and pH combine to determine the vegetative composition of ecosystems.
- Standing dead trees provide nesting and foraging habitat for many species.
Some existing snags in managed forests should be retained, but equally important
is ensuring that new snags will be recruited into the stand in the future. Small
diameter snags are adequate for some species, while large diameter snags are required
by other species and endure longer.
- Coarse woody debris from decaying logs on the forest floor provides cover, micro-
climates, and breeding habitat and should be retained in the stand. Larger
size pieces are preferable as they provide the greatest longevity and potential for
nutrient cycling and wildlife use in second-growth forests. Coarse woody debris
is rarely evenly distributed, but it should be well distributed throughout the stand,
- Tree species diversity can provide habitat for a greater variety of organisms than
that provided by a homogeneous stand. When applicable, an ecologically appropriate
variety of tree species, including hardwoods, should be retained in a stand.
- Large wildlife trees are any standing live or dead trees with special characteristics
that provide valuable habitat for conservation or enhancement of wildlife.
Characteristics include large size; condition, age, and decay stage; evidence of use;
valuable species types; and relative scarcity. These trees serve as critical habitat
(for denning, shelter, roosting, foraging, and establishment) for vertebrates, insects,
mosses, and lichens.
Proceed to Next Section: Biodiversity Management for Agriculture Outleases for
Range and Croplands