Ecological Communities and Woodland Wildlife Habitats
Marshy Glade Area near Garfield
Middle Creek winds across much of the northwestern part of Frederick in a heavily wooded section of the county. Forest surrounds much of this stream; however, in some cases, periodic flooding at the hands of beaver has resulted in the development of small ponds or open marshy glades that contain shrubby species that are well adapted to periodic flooding. Hazel alder is a prime example of such a plant having the ability to thrive in saturated conditions.
Some of the shrubby species found on this site included hazel alder, ninebark, silky dogwood, black willow, arrow wood viburnum, hazel nut and bladderwort. There were also some young sapling sized trees such as green ash, sycamore, red maple, yellow birch, elm, and swamp white oak regenerating on the site. Many of these trees will continue their growth until the site again becomes inundated with water, then only specialized species like alder and willow will persist. well.
These open areas create attractive habitat for a number of wading birds especially species like woodcock, and other birds like the catbird and red wing blackbird. Other somewhat unusual animals like a muskrat, weasel, or bear frequent these areas as well.
Once a crop field, lawn, or pasture is left fallow, a number of herbaceous and woody plants begin to colonize the area in a process known as plant succession. One stage of this process is a community known as an old field. Old fields associations are characterized by a mixture of soft, herbaceous plants like grasses, forbs, brambles, and sedges along with scattered woody plants like cedar, flowering dogwood, redbud, wild cherry, and elm to name a few. The “pioneer” species that typically colonize these sites are plants that have wind dispersed seed or seed that is disseminated by birds, or other animals. The fact that this seed can be dispersed greater distances increases the likelihood that it will be deposited in these young communities.
As an old field matures more and more trees invade the site so that a forest eventually develops. The only way to maintain this old field habitat is to reverse plant succession by disturbing the site via mowing, burning, cutting down trees, etc.
Old fields are transitory in nature usually persisting for 10-15 years before they are replaced by a young forest community. As such, these habitats are becoming a rarer site in Frederick County where open land is farmed or converted into homes, lawn, and other developments. As this community vanishes the wildlife that is dependent on these habitats becomes scarcer, such as loggerhead shrike, bob-o-link, quail etc. Providing and managing for this type of cover will benefit many of these species that are in a state of general decline.
The upper ridges and steep sloped mountainous areas are characterized by shallow rocky, infertile soils, droughty conditions, and much exposure to sunlight. All of these factors create harsh growing conditions so it is no wonder that only the hardiest of species exist here. The canopies of these ridge-top areas contain upland oaks (chestnut, black, and scarlet oak), red maple, black gum, and a variety of pine species such as Virginia, pitch, Table Mountain, and shortleaf pine. All of these trees are tolerant of dry conditions and acid soils.
A very common understory shrub growing on these ridge tops is mountain laurel an evergreen that has a particularly beautiful bloom that arises in late May or early June around Memorial Day. Another common understory species is the serviceberry one of the first trees to bloom in the spring. These sites also support an ericaceous plants like low bush and high bush blueberry along with huckleberry. Oak leaves usually litter these uplands since oaks have a lot of tannin and resist decay. The ground cover sometimes consists of a mass of moss and lichens sometimes forming a thick “mat” of vegetation on the ground.
The abundant rocks and inaccessible locations create favorable denning habitat for a number of animals like bear, bobcat, gray fox, rattlesnake, and perhaps Allegheny wood rat an endangered species known to exist in Frederick County. Although desolate, these areas support an abundance of life.
Northern Floodplain Forest
A floodplain forest is a wooded area located in or around a waterway or bottomland that is subject to periodic flooding. These floodplains can be narrow and steep in the case of small mountain streams or fairly wide and level such as the area around the Monocacy or Potomac Rivers. A narrow floodplain around a small (1st or 2nd order) stream tends to have more intense, flashy water flows and the ground does not stay wet very long. A wider more level flood plain tends to have less dramatic flood events and the soils retains the moisture longer. The variety of trees found in floodplains are those that can tolerate periods of waterlogged conditions the more level areas much more so.
Some of the trees associated with smaller upland floodplains are tulip poplar, beech, yellow birch, hazel alder, sycamore, green ash, sugar maple, hemlock, white pine, red maple, hackberry, elm, and hazelnut. Some of the more common trees in the larger floodplain forests include sycamore, green ash, boxelder, black willow, persimmon, river birch, honey locust, catalpa, silver maple, red maple, elm, and bald cypress.
By virtue of its location the floodplain forest serves a very important ecological function. These forests enhance the environment by trapping sediment, nutrients, and pollutants before the can reach the water. Forest buffers also act like a big sponge soaking up a lot of rain water before it can accumulate and contribute to flooding. The canopies of these forests chill water temperatures which is very important for cool water fish such as trout. The leaf litter, flowers, buds, sticks, and other material falling from these trees provides “detritus” to the stream which aquatic organisms process for food. By doing this, these micro and macro invertebrates convert the energy and food that aquatic organisms need to survive. When large sections of trees fall into the stream it provides “coarse woody debris” or “structure” used for aquatic habitat.
Forested areas adjacent to wetlands also provides important wildlife habitat, since all animals need water. Many migratory birds also follow streams and rivers and nest in these forests. While most animals frequent these areas to drink water there are a number of animals are closely associated with floodplain forests such as beavers, muskrats, waterfowl, fox squirrel, mink, raccoon, weasels, and otters.
Northern Hardwood Forest
The high elevation forests and north facing slopes in the northern part of Frederick County contain a tree mixture that is much more common in northern states like Michigan, Pennsylvania, New York, or Garrett County, Maryland. This is because these cooler “micro-climatic” conditions favor trees that are more adapted to northern latitudes. This is a relatively uncommon forest association in our county.
These Northern Hardwood Forests contain trees such as red and white oak, tulip poplar, beech, white ash, shagbark hickory, red and sugar maple, hemlock, cucumber magnolia, yellow birch, basswood, and white pine. The sub-canopy of these forests contain a fairly unique species mixture some being relatively rare in our county. Some of the more unique trees and shrubs found in these areas are rhododendron, striped maple, hemlock, sourwood, American hornbeam, and eastern hop hornbeam. Hemlock used to be a very common component of these transition forests but their numbers have greatly diminished due to an insect know as hemlock wholly adelgid.
Frederick County is uniquely situated so that many of the southern and northern tree varieties intermingle in our county. These small pockets of northern transitional forests form a small representative sample of vast hardwood forests lying to the north.
Oak – Hickory Forests
Oak – Hickory forests are the most common woodland communities in Frederick County occupying about 70% of the forest land base or an estimated 80,000 acres. These forests are found on rocky, well drained, upland sites that have acidic soils. Since this kind of terrain is descriptive of much of our forestland, it only stands to reason that this would be the dominant forest association.
The tree composition in our oak – hickory forests can display subtle to pronounced differences due to a variety of site factors. On the drier sites and upper slopes the dominant species may be chestnut, black, and scarlet oak along with pignut and mockernut hickory. On the lower slopes with deeper soils such species as red and white oak and possibly shagbark and bitternut hickory might join the mixture. Other trees that are part of these forests include red maple, black birch, black gum, sassafras, beech, white pine, white ash, and tulip poplar. The understory of the oak – hickory forest typically has dense woody growth composed of species such as red maple, beech, oaks, hickory, black gum, black birch, sassafras, white ash, serviceberry, flowering dogwood, mountain laurel, witch hazel, wild azalea, huckleberry, and blueberry. The herbaceous ground cover is usually pretty sparse due to the drier conditions and persistent oak leaves that cover the ground.
The oak - hickory forest developed as the result of land use practices in the early 1900’s resulting in widespread timbering of forests and large wildfires. Another factor that promoted this type of community was the onset of chestnut blight a disease that wiped out most of the chestnut trees, the most dominant tree found in upland forests at the time. The result of these factors was that trees such as the oaks and hickories that could withstand forest fires and grow in full to partial sunlight flourished. An oak-hickory forest is considered to be a sub climax forest community meaning that this species mixture will change if “forest succession” is allowed to progress. In the absence of major disturbances, the oaks and hickories will become a less dominant part of the forest once shade tolerant species like beech, red maple, black birch; black gum, white pine, and possibly hemlock get established and grow to a dominant position in the main canopy.
All plant communities undergo change and the oak – hickory forest is no exception. Various factors are influencing these forests so that oaks may no longer be the dominant species. The typical oak - hickory forest found in the early1980’s usually contained 80% oak in the canopy, and these trees were large enough to be commercially viable. This forest community was about to witness some profound changes. The mid to late 1980’s saw the leading edge of the gypsy moth invasion throughout our region. This destructive insect devours oak leaves in the early spring which leaves the tree in a severely weakened condition. Repeated defoliation by gypsy moth during the late 1980’s resulted in significant oak mortality; and, in some cases oaks were nearly eliminated from some sections of forest. In addition, merchantable oak trees were targeted during selective logging operations which removed oaks and not much else. This type of cutting resulted in an overstory that contained much less oak trees. In addition, it is unlikely that the moderately shade intolerant oak trees growing in the understory would develop into the main canopy unless they happened to be growing around a significant opening. The proliferation of deer in our county also impacted oak since deer eagerly feed on small oak seedlings. Suppressing forest fires became very important for public safety considerations but it had a negative impact on fire dependent plants like oak that benefit from these disturbances. Finally, the influence of forest succession leading to a tree association dominated by shade tolerant trees like maple, gum, beech, black birch, hemlock, and white pine created conditions unfavorable to oak. Given all these factors it is reasonable to assume that our future upland forests will contain a smaller percentage of oaks.
The oaks that are found in the oak-hickory forests are very important for forest inhabiting wildlife and to the economy. The acorns that oaks produce in the fall are a winter staple for most of our native wildlife especially deer, turkey, and squirrel. Oak trees are also highly sought after for lumber and firewood and these species are very important to the local, regional, and national forest products industry. Due to the importance of oak trees, the science of forestry has developed management practices that can be employed to help ensure that this important species be retained in sufficient numbers where desirable. Some of these practices include suppressing large gypsy moth populations, engaging in sustainable harvests that target a wide variety of species or create conditions beneficial for oak regeneration, precommercial thinnings that remove competing trees around oaks or other desirable species, tree plantings, prescribed burning operations that mimic the beneficial effects that fire can have, managing deer numbers so that oaks and other forest vegetation has a chance to grow, and placing natural or artificial barriers around young oak trees and other vegetation.
Young “Early Successional” Forests
After open land has been abandoned for a while, a number of herbaceous and woody plants seed into the area and begin growing on the site. In a few years an “old field” community develops containing a mixture of trees, shrubs, and the grasses and forbs that are a common component of fields. In time, the trees expand to the point that their crowns close together obtaining “canopy closure” and a young forest develops. These young forests are usually dominated by a mixture of early successional trees. Early successional species are usually characterized by having light wind borne seeds or seed that is enclosed in a fruit that birds eat and deposit elsewhere. These early colonizers grow fast, need plenty of sunlight, and don’t live very long compared to other trees. The role of these pioneers is to occupy the site, develop forest like conditions then give way to larger growing, longer lived trees that are usually developing in the understory. This gradual change from a fast growing, transient forest into a longer lived and more established community is known as Forest Succession.
A typical early successional forest in Frederick County might contain black locust, elm, eastern red cedar, tulip poplar, red maple, sassafras black cherry, persimmon, green or white ash, Virginia Pine, ailanthus, and mulberry trees. Some shrubby species associated with these communities include, flowering dogwood, hawthorn, spicebush, crabapple, pin cherry, nmultiflora rose, sumac, redbud, serviceberry, and plum. Depending on the stage of development these forests might have older growth trees like black and white oak, red maple, pignut and shagbark hickory, white ash, hackberry, beech, and white pine growing in the understory as well. This older growth component has the ability to attain a dominant role in the main canopy as time progresses and succession proceeds.
Sometimes these young forest communities become overrun with invasive species like multiflora rose, bush honeysuckle, autumn olive, and ailanthus to the point that the native older growth varieties do not become established. This condition will stifle forest succession and it could result in a stand of invasives once the pioneer species in the overstory begin to perish.
Dense growth of invasive species like this bush honeysuckle can disrupt forest development by excluding the older growth element from becoming established.
Early successional forests are favored by wildlife generalists such as deer, red fox, and birds like cardinals that eat a variety of foods and prefer dense cover. Animals that eat hard mast like acorns, nuts etc. are normally not very plentiful in these areas due to the lack of oak and hickory trees.
Mixed Hardwood Forests
Certain sections of forest enjoy the best of conditions, deep, rich, fertile soils, adequate moisture, and gentle topography. Examples of these areas are mountainous foot slopes, bluffs overlooking streams and rivers, coves, hollows, and north facing aspects. The forests that are found on these sites typically contain a wide variety of trees with no single species being dominant. These forests are usually referred to as cove, mixed hardwood, or Appalachian hardwood forests. Under these ideal conditions, trees grow quickly and attain a large size, especially in respect to height growth. You can tell a lot about the productivity of a forest by looking at the height of trees. The trees in a Mixed Hardwood forest are very tall compared to a forest of lesser productivity.
Some of the trees found in a Mixed Hardwood forest include tulip poplar, red oak, white oak, white ash, shagbark hickory, pignut hickory, beech, black gum, white pine, black birch, hemlock, black cherry, black walnut, elm, basswood, butternut, sugar maple and red maple. Some of the understory shrubs present in these forests include, muscle wood, ironwood, witch hazel, paw paw, spicebush, bladdernut, viburnums, flowering dogwood, and sourwood.
Along with plant diversity, these sites contain a wide diversity of wildlife, particularly birds. With the greatest variety being linked to the size of the forest, the amount of undisturbed “interior”, and the amount of canopy levels present. Where large tracts of mixed hardwood forests occur you are likely to find habitat for forest interior dwelling (FIDS) plants and animals. Many FIDS numbers are in a state of decline due mostly to forest fragmentation that is occurring in populated areas like Maryland.
Woodland wildlife habitats
Most of our native woodland wildlife lives in and around trees utilizing hollow sections of the tree or building a nest somewhere in the canopy. Trees usually develop hollow “cavities” when they grow older or die. So, it’s the larger and dead trees that have most of the cavities. Dead standing “snags” often attract insects which are hunted by woodpeckers that chisel out additional cavities in their quest for some grub.
Wildlife also utilizes downed trees for cover or habitat, living in the hollow areas or digging burrows beneath the fallen log. The male grouse perches on large “drumming” logs to attract a mate. As these logs decompose they recycle nitrogen and other nutrients back into the ground thereby enriching the soil.
Many of our woodland inhabiting birds are particular in the level of canopy they prefer to inhabit and build their nests. Some species like the vireos prefer the upper reaches; others like the nut hatches feel more comfortable in the mid-story level while others like the grouse spend most of their time on the forest floor. A forest with a diversity of canopy levels has more potential to attract a greater variety of wildlife. There is also a broad group of animals that require large unbroken sections of forest for their habitat. These animals are call Forest Interior Dwellers or FIDS.
Most woodland wildlife are highly dependent on the seeds that trees produce as a food source. The acorns produced by oaks, the nuts of hickory, beech, and walnut, the berries produced by trees like sassafras, black cherry or black gum, and the seeds, cones, and samaras produced by trees like tulip poplar, maple, and pine are very important food sources for wildlife. A large dominant “wolf” trees found in a forest produces most of the “mast” crops. Our wildlife evolved over thousands of years with the native forest plants; as such, native plants offer much more nourishment than those exotic species that might have invaded the area. Besides the mast crops, wildlife also feast on various tree parts like branches, twigs, buds, and flowers. In addition, animals will feed on the vines, mushrooms, and insects that might be associated with a tree. Wild grapes are a very important food source for many birds and mammals.
Woodland owners can enhance wildlife habitat by retaining large and dead standing trees, especially if the trees has cavities. Leaving large downed trees on the forest floor provides habitat and helps recycle nutrients. Managing for a diversity of tree species and age classes also helps to promote wildlife. Refraining from creating permanent openings in a forest aids deep woods dependent wildlife. Retaining grapevine especially where it creates a large arbor is another beneficial practice for wildlife. Also, by controlling invasive exotic species to promote native plants helps to provide high quality food source for wildlife.