Forests

Did you know that nearly half of all species known on earth live in forests? Or that forests cover nearly 80% of Conservancy lands?

The forest ecosystem

Forests provide unique ecosystem services to humans and wildlife. Below are a few reminders why trees and woodlands are amazing.

They help us breathe.

Forests produce the oxygen we need to live.

They provide food.

Trees provide fruits, nuts, seeds and sap to a host of wildlife and microorganisms, and to us humans.

They keep Earth cool.

Tree canopies create vital shade. Trees also absorb carbon dioxide that fuels global warming. Plants use some CO 2 for photosynthesis and store more CO 2 in wood, leaves and soil, sometimes for centuries.

They help us relax.

Exposure to forests has been shown to boost creativity, reduce anxiety, speed up recovery, and encourage mindfulness.

They keep soil in its place.

A forest's root network stabilizes soil against erosion by wind or water.

They are majestic!

Here at the Conservancy, we work to keep the forests healthy and abundant so that people and wildlife can continue to enjoy these benefits.

They refill aquifers.

Forests are like giant sponges, catching runoff water to replenish groundwater supplies. Soaking up surface water also protects ecosystems downstream from polluted runoff.

 
Forested areas

There are different types of forested areas on Conservancy land. A survey conducted in 2016 identified fifteen types of forest stands at Willowsford.

Because each forest stand developed with different soils, topography, hydrology, past human management and other factors, it contains different trees and understory plants. These, in turn, attract different types of wildlife, plants and microorganisms.

With so many different influences that can shape a woodland area, each type of forest stand and, indeed, each area within a type, can look and feel different, and serve wildlife and humans in different ways. See what forest stands are near where you live or hike the trails.

Forest Stand Maps

Forest Stands Within Conservancy Lands

A 2016 forest stand assessment identified fifteen forest stand types within Conservancy lands—categorized by the dominant species in the canopy. Additional tree species that were observed in the canopy, along with understory and invasive plants, are included in the following descriptions.

 
White Oak – Hickory

These stands are medium-aged to mature, with canopies that are co-dominated by white oak ( Quercus alba ), pignut hickory ( Carya glabra ), and mockernut hickory ( Carya tomentosa ). Individual red maple ( Acer rubrum ) and green ash ( Fraxinus pennsylvanica ) specimens are also present in low-lying and riparian areas. The
understory consists primarily of oak and hickory seedlings and saplings, as well as invasive shrubs, herbs and vines, including autumn olive ( Elaeagnus umbellata ), Japanese honeysuckle ( Lonicera japonica ), Japanese stiltgrass ( Microstegium vimineum ), and multiflora rose ( Rosa multiflora ).

Northern Red Oak – Hickory

These stands are medium-aged to mature, with canopies that are co-dominated by northern red oak ( Quercus rubra ), pignut hickory, and mockernut hickory. White oak individuals are present in the canopy in low densities. The understory is relatively open and consists primarily of oak and hickory seedlings and saplings. Invasive plants are present in very low densities.

White Oak – Northern Red Oak – Hickory

These stands are medium-aged to mature, with canopies that are co-dominated by white oak, northern red oak, pignut hickory and mockernut hickory. Green ash, yellow‑poplar ( Liriodendron tulipifera ) and southern red oak ( Quercus falcata ) individuals are also present in the canopy. The understory primarily consists of oak and hickory seedlings and saplings, red maple, red bud ( Cercis canadensis ) and blackhaw ( Viburnum prunifolium ). Invasive species density varies between stands and ranges from absent to high. Among the most common species are Japanese barberry ( Berberis thunbergii ), Japanese honeysuckle, Japanese stiltgrass, and multiflora rose.

Along forest edges, tree of heaven ( Ailanthus altissima ), autumn olive and royal paulownia ( Paulownia tomentosa ) were occasionally observed.

Northern Red Oak – Red Maple

These stands are medium-aged to mature, with canopies that are co-dominated by northern red oak and red maple. Southern red oak and green ash individuals are also present in the canopy. The understory primarily consists of saplings and shrubs, including hickories, green ash, oaks and blackhaw. Invasive species density is moderate and includes Japanese barberry, Japanese honeysuckle, and Japanese
stiltgrass.

Pin Oak – Sycamore

These are mature stands with canopies that are co-dominated by pin oak ( Quercus palustris ) and sycamore ( Platanus occidentalis ). The understory is densely vegetated with, primarily, black willow ( Salix nigra ) and several invasive species that are present in high densities, including small carpetgrass ( Arthraxon hispidus), autumn olive and Chinese bush clover ( Lespedeza cuneata ).

Pin Oak – Green Ash

These are medium-aged stands with canopies that are co-dominated by pin oak and green ash. Red maple and hickories are present in low numbers in the canopy. The understory is densely vegetated, with oak seedlings and saplings, eastern red cedar ( Juniperus virginiana ), and several invasive species, including Oriental bittersweet ( Celastrus orbiculatus ), Japanese honeysuckle, Japanese stiltgrass and multiflora rose – in high densities.

Pin Oak – Green Ash – Red Maple

These stands are medium-aged to mature with canopies that are co-dominated by pin oak, green ash and red maple. Yellow-poplar, hickories, and sycamore are also present in the canopy in low numbers. The understory composition varies within individual stands but is generally comprised of boxelder ( Acer negundo ), red maple,
red bud, spicebush ( Lindera benzoin ), black gum ( Nyssa sylvatica ), oaks, and elms ( Ulmus spp.). Invasive species density ranges from moderate to high. The most common include Japanese barberry, autumn olive, Japanese honeysuckle, Japanese stiltgrass, and multiflora rose. Less frequently observed were garlic mustard ( Alliaria
petiolata ), small carpetgrass, Chinese bush clover and Chinese privet ( Ligustrum sinense ).

Virginia Pine

These are mature stands with canopies dominated by Virginia pine ( Pinus virginiana ). Additionally, eastern red cedar and oaks are present in low numbers in the canopy. The understory consists primarily of red maple, eastern red cedar and black gum. Invasive species are present in low to medium densities and include Japanese honeysuckle and multiflora rose.

Virginia Pine – Oak

These stands are mature with canopies that are co-dominated by Virginia pine, northern red oak and southern red oak. The understory consists primarily of red maple, hickories, huckleberry ( Gaylussacia baccata ), black gum, oaks and sassafras ( Sassafras albidum ). Invasive species are present in low to medium densities and include Japanese honeysuckle, Japanese stiltgrass and multiflora rose.

Eastern Red Cedar

These stands are dense, medium-aged forests with a canopy dominated by eastern red cedar. Red maple, yellow-poplar and oaks are also present in low numbers in the canopy. The understory primarily consists of red maple, red bud and flowering dogwood ( Cornus florida ). Invasive species are present in high densities and include Japanese honeysuckle and Japanese stiltgrass.

Yellow-Poplar – Hickory – Ash

These stands are medium-aged to mature with canopies that are co-dominated by yellow‑poplar, hickories and green ash. Red maple, pin oak, sycamore and elms are present in low numbers in the canopy. The understory primarily consists of red maple, hickories, ashes and several invasive species including garlic mustard, Chinese bush clover, Chinese privet, Japanese honeysuckle, Japanese stiltgrass and multiflora rose, which are present in low to high densities.

Yellow-Poplar – Black Cherry

These stands are medium-aged with canopies that are co-dominated by yellow-poplar and black cherry ( Prunus serotina ). The understory is densely vegetated, primarily by invasive species in high densities, including tree of heaven, garlic mustard, autumn olive, Japanese stiltgrass, multiflora rose, mile a minute ( Persicaria perfoliata ) and Japanese wineberry ( Rubus phoenicolasius ).

Eastern Red Cedar – Pin Oak – Sycamore – Black Walnut (Transitional Forest)

This is a medium-aged, transitional forest stand with a canopy that is co-dominated by eastern red cedars, pin oak, sycamore and black walnut ( Juglans nigra ). Boxelder, red maple, and green ash are present in low numbers in the canopy. The understory is densely vegetated and consists primarily of hackberry, flowering dogwood, persimmon ( Diospyros virginiana ), spicebush, black cherry and several invasive species. Among the invasive plants, autumn olive and Japanese stiltgrass are present in the highest densities. Garlic mustard, small carpetgrass, Japanese barberry, bull thistle ( Cirsium vulgare ), multiflora rose and mile a minute are present in moderate densities.

Fragmental Forest Stand

This stand is medium-aged and possesses a semi-open canopy, dominated primarily by tree of heaven and royal paulownia. Silver maple ( Acer saccharinum ) and black walnut were observed in the canopy. The understory features a dense shrub layer, comprised primarily of sawtooth blackberry ( Rubus argutus ) and invasive shrubs and vines in moderate to high densities, including autumn olive, Japanese stiltgrass, multiflora rose, mile a minute and Japanese wineberry.

Tree-lined Fence Rows

Tree-lined fence rows divide fields and meadows within Conservancy lands. Mature eastern red cedar trees are often at the center of these linear features. These tree-lined areas consist of relatively mature trees. In addition to eastern red cedar, red maple, black walnut, black gum, black cherry, pin oak and black locust ( Robinia pseudoacacia ) are present. Invasive species, including tree of heaven, Japanese honeysuckle and royal paulownia are prevalent.

 

Forest Management

Management options for our forested areas vary depending on several factors, such as:

•     The composition of trees and other plants within the forest stand
•     Stand age and condition/health
•     Presence and regeneration of desirable species
•     Presence of invasive plants, pests and diseases
•     Deer pressure
•     Stand size
•     Use of the forest stand (riparian buffer, wildlife habitat, recreation
•     Proximity to areas requiring buffer (homes, wetlands) and to areas of high use (recreational areas, amenities)
•     Access for maintenance
•     Available resources for management

Management guidelines

More work is needed to develop specific management guidelines for forest stands on Conservancy property. Some general management options that apply to forested areas throughout the Conservancy include:

 
Removal of potential hazard trees

The Conservancy removes dead, damaged or diseased trees that pose a threat of falling on trails, roads, structures or recreational facilities, or otherwise present a safety hazard.

Trees in various stages of decline are part of a natural woodland environment. If there is no danger to persons, structures or trails, leaving standing dead trees (called “snags”), tall stumps from 6-20’ tall (called “spars”), or uprooted trees provides habitat and food to many kinds of wildlife, plants and microorganisms.

Forest Enhancement

The Conservancy aims for a high diversity of native plants to promote healthy habitat and diverse native wildlife—by promoting natural regeneration, and through targeted restoration efforts. Check out the Current Projects section for work that is underway.

Pests and Diseases

Tree pests and diseases like Chestnut Blight, Hemlock Woolly Adelgid, Dutch Elm Disease and Emerald Ash Borer continue to threaten trees and forests. While there are treatments for some pests and diseases, treating entire tree stands in a forest environment often is not economically feasible for the Conservancy, and not environmentally responsible.

Ways to prevent their spread include limiting transport of firewood and other materials that carry pests and diseases; deer population control to support natural regrowth of healthy native trees; and managing forest habitat for overall health and resilience.

Examples of the Conservancy’s efforts include providing firewood at campsites and for residents using wood from Willowsford; implementing a deer management program; habitat restoration; education; and programs that encourage wildlife to support natural pest control.

Deer Management

In areas where deer populations exceed the natural carrying capacity of a given ecosystem, acorns, nuts and seedlings are consumed in quantities that prevent regeneration of desired species including native trees and understory plants. This is evident in stands where a conspicuous “browse line” is present and few or no desirable seedlings or saplings exist below 8’ in height. The forest floor may be covered by undesirable, in many cases invasive species.

Excessive deer pressure must be mitigated to regenerate and maintain healthy stands. The Conservancy has implemented a deer population management program as a long-term, cost effective method for managing the deer population.

Replanting trees and other native vegetation in certain areas, and regenerating stands with very high deer pressure, may require fencing to allow desirable species to establish. Recommended deer exclusion fences in hardwood forests are woven wire at a minimum height of 8 feet, anchored to the ground, and require a greater investment of resources.

Management of Challenging Tree Stands

Smaller stands sometimes face particular challenges. Our primary goal is to maintain natural forest habitat that benefits diverse wildlife. For certain smaller stands that have been impacted by wind and other damage and that are in close proximity to homes and amenities, management practices that result in a more park-like setting within the stand may be chosen as a maintenance alternative—as determined by the Conservancy and based on the forest management factors mentioned above.

Management of Challenging Tree Stands

Invasions by non-native species are a significant threat to our forests, causing habitat degradation and expensive eradication efforts.

Invasive plants out-compete and replace native species, resulting in lower ecosystem diversity and stability, with less food, shelter and habitat for wildlife. Invasive species also impact the aesthetic value of a woodland by reducing the abundance of desirable native plants.

Many forest areas within the Conservancy are plagued by non-native invasive plants. The following species are present on Conservancy lands.

Willowsford Conservancy

44095 Pipeline Plaza, Ashburn, VA 20147

Phone: 571-252-3980

info@willowsfordconservancy.org

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Willowsford Farm Stand

23595 Founders Drive, Ashburn, VA 20148

Phone: 571-297-6900

farm@willowsfordfarm.com

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