Good news. There are still isolated tracts of forest in Maryland
which posses both the characteristics of old growth and most of the
species that were present when Europeans first came to America.
While the majority of these stands are not ³virgin,² which means
never touched by axe or saw, they were nonetheless lightly cut and
are returning to the condition which ecologists recognize as old
growth.
Four Stages of Forest Development
What is ³old-growth² and how does it differ from the woods you
generally see? To best explain old growth it is necessary to
understand the four basic successional phases of a forest.
Stage 1: Reorganization
The first stage occurs immediately after a disturbance in the
forest caused historically by fire and wind or today also by
people. This stage is termed reorganization and generally last
less than twenty years during which time many nutrient cycles and
other soil processes act to stabilize the area. As this stage is
completed, seedlings and sprouts of woody plants striving to
become the canopy of the new forest shade the soil.
Stage 2: Aggradation
The second stage, aggradation, may last for well over a century as
the trees rapidly grow in height, as well as girth. Trees
accumulate nutrients and biomass faster during this stage than
any other. Thus, to maximize the economic return, nearly every
acre of forest commercially managed for wood products is cut
during this early stage in succession. Clearcutting of forest in
the aggradation stage is the preferred silvicultural method to
start the regeneration of a new stand.
Stage 3: Transition
However, if forests are permitted to continue to evolve naturally,
the trees will begin to slow their rate of growth as their crowns
compete for sunlight and their roots compete for water and
nutrients. Shading from neighboring trees, disease, insects,
fungi, as well as damage from tree falls, begin to thin out the
trees in the forest. Less and less of the nutrients in the
ecosystem are tied up in living tissue; nutrients increasingly
accumulate in organic matter on and in the forest soil. As the
soils enrich and the amount of dead wood accumulates in the system,
the abundance and diversity of life responds to the increasing
food resources and habitat complexity. This third stage of forest
succession is termed transition to denote these changes.
Stage 4: Steady State
Eventually, in less than two hundred years from the initial
disturbance, the forest¹s nutrient levels and biomass stabilize
so that a steady state, the final stage of forest development,
will result. Now the death of a tree is balanced by the
germination of a number of seedlings. Over time throughout the
stand, the nutrients and life entering the system roughly equal
the nutrient loss and death in the forest. A complete life cycle
is established and maintained. This condition, called ³old-growth²
by ecologists, will exist indefinitely until humans or natural
occurrences disturb this balance.
Old-Growth Characteristics
Old-growth forests differ significantly from forest managed for
wood products, those maintained to the aggradation stage. As
compared to younger forest, old-growth forest are characterized
by larger trees, more standing dead trees which are important for
wildlife, more downed logs, a more uneven canopy with many gaps
and different tree sizes, greater variation in the light level,
temperature (mostly cooler), and moisture (more humid) on the
forest floor, and greater complexity in overall forest structure
(multiple, indistinct growth layers, and greater heterogeneity).
Because of these differences and complexities, the diversity and
abundance of life supported in an old-growth ecosystem is far
greater than that found in the early successional stages of a
forest.
Maryland's Heritage
Inability to interpret old growth conditions, priority
consideration for retention during the land development process,
destruction of old-growth ecosystems and the fragmentation and
simplification of the forest is compromising some plant and animal
species, including songbirds that require interior forest
conditions.
The Maryland Natural Heritage Program and others are beginning to
identify and study remaining patches of the State¹s old-growth
forest. So far, research has located only a few completely
virgin tracts larger than 100 acres. However, they have identified
a good number tracts of forest containing old-growth, as well as
larger areas (often surrounding pockets of old-growth) where the
forest was only cut once or twice, often selectively, (highgrading)
and is now in transition to the steady state.
We need to seriously consider the protection of old-growth forest
conditions in Maryland. We also need to adequately protect
Maryland's biological diversity by setting aside ecologically
viable blocks of contiguous forest to allow it to revert to old
growth.
Although unintentional, the Maryland Forest Conservation Act (FCA)
has inadvertently promoted old growth throughout the State. Since
1991 when enforcement of the Act began, the average forest set
aside (not including forested floodplain) of any given development
tract has been approximately 20 percent. The language regarding
their long-term protection has in general, only recognized passive
recreation as a legitimate use. This will result in numerous small
tracts being allowed to revert to old growth over ecological time.
Less than 5 percent of all dedicated FCA lands include language for
lumbering, which is a landowners legal right, if they should choose
to do so. This is because a cut forest meets the legal definition
of a standing forest according to the Act.
ESA, Inc is heavily involved with performing all aspects of forest
stand delineation and forest conservation plans for our clients.
We have observed that when a client has land with priority forest
retention areas that include floodplain, wetlands, steep slopes
and/or highly erodible soils and still are not at desired
threshold set-asides or break-even point, that we then consider
forest age as possibly the next most important criterion for
retention. A 60-year old forest is inherently more valuable than
a 30-year old forest. It may take upwards of 60 years + for a
stand to reflect an endemic shrub layer. The next most important
retention consideration would be to retain forest in a manner that
would maximize the total forest area, versus increasing the edge
effect.
ESA, Inc. has developed numerous ecological restoration plans for
forest retention areas, receiving aff or reforestation credit by
improving upon existing conditions, before attempting to create
new forest situations. We have been able to manage for nuisance
alien plants or taken a sapling stocked (1 to 5-inches diameter)
stand and advance seral succession by thinning (crown touching) to
push basal growth, thereby creating a more attractive forest
setting during the life expectancy of residents who may abut an
FCA subdivision greenspace dedication.
