Display to header level
With the decline of natural disturbances like fire and conversion of land to development, shrublands are decreasing in prevalence and extent. Management can help maintain and improve shrublands to support the wildlife that rely on them.
Shrublands are plant community types dominated by shrubs, which are multi-stemmed woody plants less than 15 feet tall. Naturally occurring shrublands may include the occasional tree, but tree canopy covers less than 40% of the area. The growth of trees is limited by physical environmental factors (poor and shallow soils), competition from dense shrub species, natural and anthropogenic (human-caused) disturbances, or some combination of those factors. Shrublands support graminoids and forbs (herbaceous species), but, unlike grasslands and meadows, they generally lack a consistently dense layer of non-woody species.
Shrublands can be divided into two general community types for management planning purposes: successional and persistent shrublands. This distinction helps us understand the possible goals and objectives for management.
Successional shrublands represent a transitory ecological state and are the result of disturbances, such as wildfire or windthrow, or direct human intervention in the landscape—clearing for agriculture or timber harvest and subsequent abandonment. Successional shrublands are often unmanaged landscapes following an ecosystem-altering event. Successional shrublands may be composed of native or introduced plant species, or both; the species found there are those that can take advantage of the disturbance by quickly colonizing open lands. The intermediate successional stage shrublands, often called thickets, usually grow into the forest stage in just a few years unless exposed to frequent tree-killing disturbance. Regular disturbance, such as forestry mowing, is necessary to prevent successional shrublands from progressing to forest, if maintaining shrublands is the management goal.
Previously, shrublands were relatively abundant due to Native American burning for thousands of years and agricultural practices over much of the past three centuries. Until recently, clearcutting and farmland abandonment across the region continually produced new shrubland to replace acreage steadily lost to forest succession. Shrubland abundance has rapidly declined as forests have matured, informal burning for ecological management was curtailed, and housing developments have consumed more recently abandoned farmland.
Changes in land use practices and the advent of widespread fire suppression have resulted in the succession of open shrublands to dense shrub thickets and then forests. Many of the species associated with successional shrublands cannot persist in the later stages of succession. For example, pitch pine are not known to germinate and establish without fire or soil disturbance, and several bird species that breed only in shrublands have declined with the downtrend in shrubland area in Pennsylvania.
Persistent shrublands have much longer lifespans compared with the successional variety. They are often composed of shrub species adapted to harsh conditions, such as poor soils, and may persist over long periods of time without disturbance or management. These communities are often rare and are of conservation concern, as they are composed of habitat specialists and support rare species that have specific adaptations for life in these harsh conditions. Shrublands on rocky ridgetops dominated by low sweet blueberry, mountain-laurel, or scrub oak are examples of naturally occurring shrublands, where conditions are so harsh, very few other plants survive, and the ones that are found are often stunted and low-growing. Note that evergreen shrubs (two species in our region—rosebay rhododendron and mountain-laurel) will not tolerate a management regime of mowing or burning, but many native deciduous shrubs resprout prolifically from their roots after cutting or fire.
Shrublands comprised of native plants provide many of the same environmental benefits as forests and some unique ecological benefits, including habitat for threatened wildlife. Persistent shrublands generally host a number of rare plant species and an exceptional diversity of rare butterflies, moths, and other insects. The diversity and presence of rare plant species in many native shrublands is correlated with the overall age of the plant community, with newer stands less likely to host rare plants.
Shrublands, both successional and persistent, are especially important for a number of habitat-specialist bird species. Due to conversion of natural areas to development and agriculture and natural successional of abandoned cropland and pastureland to forest, many of these species are uncommon or declining in our region; those ranked as species of greatest conservation need in the current Pennsylvania Wildlife Action plan are golden warbler, blue-winged warbler, prairie warbler, yellow-breasted chat, willow flycatcher, eastern towhee, field sparrow, and American woodcock.
In addition to providing habitat for wildlife, shrublands are important sites for birding and hunting. Managing successional shrubland for game species such as American woodcock, ruffed grouse, and northern bobwhite is a major focus of habitat managers on both state and private land in Pennsylvania.
There are few shrublands in Pennsylvania that are in an ecologically healthy condition. To qualify as an ecologically healthy shrubland, a site must be dominated by native shrub species and free of invasive plants. Shrublands near urban areas are therefore relatively poor in condition because shipping ports, croplands, and gardens have been points of entry for exotic species for centuries. Those that are particularly invasive in shrublands include autumn-olive, Japanese barberry, introduced buckthorns (common and glossy), burningbush, introduced shrub honeysuckles (Amur, Morrow’s and Tartarian), jetbead, multiflora rose, privets (border and common), introduced viburnums (doublefile, linden, and Siebold), wineberry, and butterfly-bush. Abandoned farm fields and pastures—the usual precursors of shrublands in the region—also typically receive a plentiful supply of invasive species’ seeds.
Key features of a healthy shrubland include:
Field inventories can be done to monitor a shrubland’s health and identify issues. This will help with determining management goals and actions. An effective inventory should seek to assess the above key features and their condition. While inventories are important, they can be resource intensive. The categories Good, Better, and Best outline three different levels of inventories.
The types of plant communities found in an area can tell us a lot about a site. Plant community surveys provide information about plant species presence, the structure and composition of the plant community, soil chemistry, geology, presence of wildlife habitat, and quality of the entire landscape.
If the shrubland is a shrub wetland type (indicated by the presence of wetland hydrology, wetland vegetation, wetland soils), follow guidance for inventory and stewardship of wetlands (see Wetlands Management chapter).
Good—Determine if the community is successional or persistent (this may require advice from a knowledgeable ecologist or botanist). Determine the size of the shrubland within the site. Subsequent assessments should be conducted to monitor change in the size of the shrubland or patches of shrubland over time.
Better (in addition to Good)—Identify the several most abundant species, including those that are dominant. See if there are distinct patches dominated by a different species or set of species. This will help determine what specific community or communities are present, which in turn will influence management goals and methods.
Best (in addition to Good and Better)—Determine the specific community type(s) that make up the shrubland according to the Pennsylvania Terrestrial and Palustrine Community Classification 2nd edition (see Related Library Items). Map the boundaries and describe each plant community within the site.
2. Determine the shrubland’s value to wildlife
Assessing the habitat quality of the shrubland and what wildlife species it currently, or could, support will inform management decisions.
Good—Based on the site and the types of habitats at a site, determine what kinds of wildlife the shrubland may support. The Conservation Opportunities Areas tool can inform this determination (see Related Library Items).
Better (in addition to Good)—Collect and review any information available on the shrubland of interest. Consider not only natural communities but also specific species that are present in the shrubland. Consult local and state agencies, review community science sites, review the Pennsylvania Natural Heritage Program’s (PNHP) website and Natural Heritage Areas (NHAs), and talk to local experts to assess what wildlife species may be present.
Best (in addition to Good and Better)—Perform field inventories to determine what species and habitats are present and ground-truth or enhance any information that has already been collected. Tailor the inventory to the taxa or habitats that are likely to be most valuable or rare or widespread in the shrubland. These may become the central focus of any monitoring or management that will take place in the future.
3. Assess condition and viability
Assessing the condition and viability of an ecosystem provides the baseline data to develop a stewardship, restoration, and management framework for a natural area. A model framework for ecological assessments (often called ecological integrity assessments, or EIAs) has been developed by NatureServe to guide development of site assessment methods that are used to assess and monitor the ecological condition and viability of a site (see Related Library Items).
Good—Review aerial photos for signs of disturbance, encroachment, invasive species cover, and general landscape condition. Consider any data available on use by wildlife and presence of specific habitats or species. According to the NatureServe EIA, this type of assessment is often referred to as a “Level 1” or landscape-level assessment. In Pennsylvania, landscape-level assessments may be conducted through the use of a tool called the Pennsylvania Landscape Condition Model (LCM), which is a protocol that can be applied in a geographic information system (GIS) (see Related Library Items).
Better (in addition to Good)—Based on the information from above, further investigate through field visits possible impacts including hydrological alterations (dams, channels, drainage tiles, etc.), presence of invasive species, particularly if dense and widespread, and any obvious disturbance (timbering, mowing, structures, etc.). This step is referred to by NatureServe as a “Level 2” assessment and requires a basic understanding of ecological processes and knowledge of local flora, fauna, and funga. A trained botanist or ecologist is not necessarily required to perform a Level 2 assessment. For the Level 2 assessment the shrubland is evaluated for a set of ecological stressors, such as invasive species or presence of trash. A level of severity (usually 1-3) is assigned to each stressor present. This stressor checklist results in a condition score for each anthropogenic (or human-caused) stressor. Note any changes and further investigate with field observation and consultation with experts.
Best (in addition to Good and Better)—A formal site visit should be conducted by a trained botanist or ecologist to determine the plant composition of the site and assess ecological variables that contribute to the ecosystem’s condition and viability. The plant species are extremely important in assessing the ecological quality of a site; they are indicators of condition that can be monitored over time to see if site quality is maintained or is declining. For this level of assessment, called “Level 3” by NatureServe, a full species list and quantified community composition, often assessed using fixed quadrats or other methods, is determined by a trained botanist or ecologist. A wetland delineation is often helpful and multiple assessments are required to determine change over time. If the shrubland is determined to be a wetland, see Wetlands Management chapter.
Management goals will depend in part on the type of shrubland present. As discussed previously, persistent shrublands in Pennsylvania are naturally occurring and resist encroachment by trees in part due to plant species composition and in part due to soil characteristics, some of which are in turn produced or influenced by the plants themselves. They may require human intervention to recreate natural disturbances. Successional shrublands require ecological or human-caused disturbances to persist. After determining the type of shrubland present, land managers will have to decide if they want to retain a shrubland, which would require maintenance and possibly restoration, or if they want to allow it to transition to forest or convert it to meadow. Conversion to forest or meadow would likely be the favored approach when a shrubland is degraded, when a shrubland is successional, and/or when a shrubland is a small patch is a larger area of forest or meadow that could provide interior habitat.
These decisions can inform long-term goals for the shrubland. Examples of long-term goals include maintaining and conserving important habitat connections to the landscape and restoration to a previous or preferred state.
In addition to long-term goals, all shrublands will likely require short-term goals directed toward specific problems or needs. Short-term goals include: control or elimination of certain invasive species, control or elimination of certain tree species, adding interpretive signage, erecting nesting boxes, and various other stewardship practices.
Broadly, the management of shrublands can fit into three categories: maintenance, restoration, and conversion. The type of management undertaken will dictate many of the goals that are decided upon for the shrubland in question.
For the purposes of this chapter, maintenance is used in reference to successional (not persistent) shrublands. Management of persistent shrublands is covered in Restoration, below. The primary threats to successional shrubland communities are invasive plant species and succession to forest in the absence of management or natural disturbances, plant pests, and deer browsing. Other threats include loss of this community due to development of cell phone towers, wind turbines, and utility lines, or crushing by visitors on ATVs.
Maintenance is an ongoing, permanent necessity for all successional shrublands by definition. Maintenance involves control, management, or mitigation of threats to the overall integrity of the community. It also includes maintaining natural disturbance processes or artificially replicating them to limit tree growth and prevent the transition from an open community type to a closed canopy forest.
Maintaining successional shrublands can be accomplished either by mowing, selective cutting, or applying prescribed fire to approximately one-third of the shrubland area every 3-10 years, rotating the area being treated. Treatments may need to be closer to every three years for shrublands that are heavily populated by trees or invasive plants. Treatment frequency may then decrease over time. Reintroducing disturbance on a rotational basis rather than treating the entire shrubland at once will provide refugia for wildlife species that are dependent on the shrubland, as well as creating a multi-aged shrubland that provides more types of habitat.
Determine the limits of available mowing machinery (how large of a tree or shrub can be cut) to set mowing frequency. In most cases, it is advisable to engage a contractor with specialized equipment to perform this work. Mowing should be done wildlife is less vulnerable to disturbance, that is, during the non-growing season (roughly mid-November to mid-March in southeastern and southwestern Pennsylvania and beginning earlier in the fall and ending later in the spring to the north and at higher elevations). A late winter or early spring mowing (prior to April 1st) is best.
An alternative method to maintain native successional shrubland is to selectively remove, through cutting or herbicide application, invasive woody plants and seedlings and saplings of tall-growing tree species, while leaving tree species that typically do not exceed 25 feet in height (see Native Plant Materials).
Fire can be part of a management strategy to maintain successional shrublands, although it is more often used to restore and maintain persistent shrublands. Native Americans used fire to manage the landscape for thousands of years, which selected fire-adapted species to dominate native grasslands, meadows, and shrublands. Prescription burning should be conducted only by well-trained personnel and in accordance with federal, state, and local laws. See the Prescribed Fire chapter for more information on the benefits of and regulations for prescribed burns.
Regardless of the method of disturbance, land managers will likely have to deal with a variety of stressors. More information can be found below under Addressing Issues.
Restoration, as we use the term in this Handbook, applies only to remnants of persistent shrublands that have been degraded as the direct or indirect result of human activities. Management of persistent shrublands is particularly important as these shrublands typically have a high conservation value. The Society for Ecological Restoration International (SERI) defines ecological restoration as “an intentional activity that initiates or accelerates the recovery of an ecosystem with respect to its health, integrity and sustainability.” In most cases, restoration of persistent shrublands includes removal or control of introduced invasive species, physical removal of tree species, and reintroduction of fire or another vegetation-clearing process that mimics at least some of the effects of fire.
Management techniques need to be especially adapted to the specific community type and its distinctive set of species of conservation concern. In many areas, native shrublands that were historically present have completely succeeded to forest. Research should focus on identifying specifically where shrublands once existed, identifying characteristics of optimal restoration sites, and identifying successful management techniques for restoring persistent shrublands. A good first step is to check historical aerial photos, which date back to the late 1930s-early 1940s for most of Pennsylvania and back to the 1920s for a few areas (see Penn Pilot under Outside Resources, below). Help from a qualified ecologist is advised to develop a restoration plan tailored to the needs and opportunities of a specific site.
As with successional shrubland management, managers should plan on mowing, selective cutting, or applying prescribed fire to no more than one-third of the shrubland area each year and repeating treatment in each patch every 3-10 years. Because of the extraordinary conservation importance of persistent shrublands, it is crucial to maintain refugia from fire or other treatments for animal species, some of which may be endangered or threatened, and it is just as important to vary the frequency of treatment across the landscape to provide for the different habitat needs of the many species that depend on shrublands for survival.
Successional shrublands that have few native plants and a high proportion of invasives can be considered for conversion to forest, grassland, or meadow if increase the interior area of these cover types to benefit forest-interior or grassland-interior species.
Converting to forest can be either the easiest or hardest road to take depending on the status of succession (the density, height, and species composition of established native tree seedlings and saplings) and the level of degradation by invasive plants. It will be the least costly if native trees are poised to dominate the site and the amount of invasive plant material is small. It will be the most difficult option if native trees are sparse and invasive plants are prominent. To convert to native forest, land managers should:
(1) Identify native trees and release them from competition with invasive plants by cutting or wick application of herbicide. Native trees can usually outcompete invasive shrubs, but not invasive vines and trees.
(2) If necessary, augment natural tree regeneration by planting native tree seedlings. This will require a spacing of between 10 feet × 10 feet and 20 feet × 20 feet. See the Tree Selection and Planting chapter for more information.
(3) Use protective measures such as fencing, tree shelters, or flexible tree guards to minimize deer damage to both wild and planted seedlings. See the Tree Selection and Planting chapter for more information.
(4) After planting, reduce plant competition, either through selective herbicide application to kill vegetation, particularly sod-forming grasses, around the base of each tree once or twice annually and/or by mowing at least four times during the growing season, until the tree canopy exceeds 60% cover.
Converting to grassland or meadow will require removing woody plants and invasive plants. The land will need to be cleared and planted with a seed mix, plugs, or both in different patches. Which option is best will depend on the size of the area to be converted and the resources available. More information on creating a grassland or meadow can be found in the Grassland and Meadow Management chapter.
Some land stewards may have shrubland management as a goal but the land under their care lack this cover type. They may wish to provide and maintain habitat for shrubland-dependent species of wildlife, increase habitat diversity, or create a gradational transition from an existing developed area or grassland/meadow to an existing full-stature forest, to reduce the exposure of forest edges to light, heat, and wind, limit human access, or simply for aesthetics.
Shrublands can be created to address these goals. It is best to limit new shrubland creation to already-disturbed areas such as abandoned farm fields, strip mines, brownfields, lawns, or areas with a very high proportion of invasive plant cover. Existing forest, especially if mature or old-growth, and existing grassland or meadow dominated by native herbaceous species are too scarce and valuable as wildlife habitat to be replaced by a new community whose future conservation value is highly uncertain. However, the value to wildlife of created shrublands is sure to be an improvement over conditions on degraded lands.
Shrublands can be created by allowing natural succession to do most of the work if there are few invasive plants present. If invasive plant cover is significant, land managers should control the invasive species and immediately plant native species to claim that growing space. Planting shrubs can also speed the establishment of a shrubland in areas with few invasive plants and it is a necessity on lands with no shrub cover to start with. In either scenario, land managers will need to control invasive plants and protect shrubs from deer until they are established enough to withstand moderate deer browsing and rubbing. This is generally when shrubs are at least 5-10 years old.
Shrubs can be protected from deer browsing by fencing the entire area, or rotating fencing among smaller patches of shrubs until an entire area is covered, or by protecting individual shrubs with wire exclosures, depending on the size of the area, the number of shrubs to be planted, and the land manager’s tolerance of delay until full coverage is achieved. Where large areas are to be fenced until shrubs have grown tall enough to persist despite overbrowsing, a less expensive alternative to a fence 8-12 feet tall that deer are unable to jump over is a pair of parallel fences 4 feet tall and 10 feet apart. Research in Pennsylvania has shown that deer will generally be deterred by this type of fencing, leading to a high survival rate of both shrubs and tree seedlings (Sweeney and Dow 2019). Despite the need to build roughly twice as many linear feet of fence, the shorter fences require far less sturdy and deeply driven fenceposts. They are more conducive to temporary installation because they are relatively easy to disassemble and reassemble in different locations.
For all shrublands, there will be issues to confront. Assessing the severity of problems and how critical it is to address each one through active management is an important step before management plans are created. Setting the goals for any type of management will be essential to guide ongoing management and ultimately for measuring progress and success.
As with all other vegetation cover types, invasive plants can degrade native shrublands. Invasive shrubs (multiflora rose, introduced shrub honeysuckles, privets, Japanese barberry, autumn-olive, glossy buckthorn, etc.) degrade a shrubland by playing little or no role in the food web and by crowding out native plants that are essential to ecosystem health. While invasive shrub species can provide cover for shrubland birds, they do not provide significant nutritional value for wildlife. Native insects are poorly adapted to live on them or avoid them entirely, and all of the other wildlife that depend on insects, including nestling and adult birds, are unable to sustain population levels that existed before the invasives arrived. Native pollinators rely on the native plant species they evolved with; many are unable to survive on invasive plants because their larvae feed only on natives. Ironically, butterfly-bush escapes from gardens into the wild where it can crowd out larval host plants, thus destroying essential butterfly habitat. Invasive plants can be especially problematic in successional shrublands where they can outcompete native shrubs for limited water, light, soil nutrients, and space, unconstrained by deer and insect herbivory. The lack of natural disturbances only exacerbates the impacts of invasive species.
The following management strategies are recommended as general approaches to helping managers of shrubland ecosystems manage and control invasive plant species. More information about the problems caused by invasive plants and more details for management are included in the Invasive Plants chapter.
Good—Control invasive plants in highest quality areas. Control invasive plants that pose a risk to humans or animals (e.g., poison-hemlock, giant hogweed). Be alert for new invasive species and control them before they begin spreading from their initial beachhead.
Better (in addition to Good)—Control invasive plants in areas of moderate quality, as well as the highest quality areas. Educate visitors about invasive plants; consider installing one or more trailhead boot brush stations with explanatory signs.
Best (in addition to Good and Better)—Systematically control invasive plants throughout the entire property, following prioritization strategies. Work with nearby landowners to collectively manage invasive plants.
Spongy moth (Lymantria dispar) outbreaks also threaten some shrublands that have a strong component of oak species in the tree and shrub layers (two of Pennsylvania’s oak species are shrubs—scrub oak and dwarf chinquapin oak); quaking and bigtooth aspens, willows, crabapples, hawthorns, and speckled and smooth alders are also susceptible. Outbreaks may favor the conversion of oak-dominated communities to heath-dominated communities. Signs of outbreaks include defoliation of oaks and egg masses on tree bark, wood piles, dead branches, and building materials. The egg masses are small, oval, light brown masses attached to a surface. Eggs are deposited in late summer or fall and hatch in the spring.
In the mid-20th century enormous ecological damage was done by broadcast spraying insecticides on spongy moth-infested forests. That approach backfired, since the spongy moth populations rebounded faster than those of their insect predators, which led to even more severe outbreaks. More importantly, the entire food web collapsed with the indiscriminate killing of nearly all insect species, causing populations of many wildlife species to crash. However, in the 1970s a virus was discovered that infects only spongy moths and no native insects; it is available as a control agent under the name Gypchek from the U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) and the Forest Service, which also supply instructions for its use (see Outside Resources, below). Small spongy moth infestations can be controlled by manually destroying egg masses or injecting affected trees and shrubs with a systemic insecticide. Any spongy moth control effort needs to balance the maintenance of oaks and other susceptible trees and shrubs with overall ecosystem health, using methods that minimize impacts on other insects. Prioritizing areas of infestation for treatment and leaving some untreated is an option if resources are limited, but additional management may be required to monitor for and control invasive species in canopy gaps resulting from tree death from spongy moth infestations.
As of 2024, there is limited information available about the impact of climate change specifically on shrublands in Pennsylvania. Research has been done in the West, finding that increased disturbances like fire will result in the conversion of forests to shrublands and grasslands (Kodero et al. 2024). An increase in disturbances in Pennsylvania, including flooding and possibly wildfire, could have similar results, particularly for successional shrublands.
However, there are potential climate change impacts that may have negative repercussions for some shrublands. Numerous climate models based on various emissions rates predict that Pennsylvania will get warmer and wetter, although with longer and more frequent droughts. It is possible that increased temperatures and precipitation may speed the otherwise very slow encroachment of forest trees into persistent shrublands in such a way that prescribed fire or forestry mowing would have to be applied more often to maintain these communities. Due to the general lack of connectedness among persistent native shrubland ecosystems across the larger landscape, species dependent upon them have minimal opportunity for dispersal and movement as climate conditions change. In some cases, translocation or propagation from locally collected seed for out-planting may be the only way to ensure that key plant populations, particularly of rare species, can survive.
Additionally, Pennsylvania will see warmer winters. This is an issue as cold winters help keep invasive plants in check. Instead, invasive plants will be less restricted in their ranges with warmer winters, allowing species such as kudzu that were more common south of Pennsylvania to move north. This is more likely to negative successional shrublands than persistent shrublands, as they are more susceptible to invasive plants in general.
Good—
Better (In addition to Good)—
Best (In addition to Good and Best)—
Chamberlain, S. and H. Ingram. 2012. Developing coefficients of conservatism to advance floristic quality assessment in the Mid-Atlantic region. Journal of the Torrey Botanical Society 139:416-427. doi.org/10.3159/TORREY-D-12-00007.1
Faber-Langendoen, D., J. Lemly, W. Nichols, J. Rocchio, K. Walz, and R. Smyth. 2019. Development and evaluation of NatureServe’s multi-metric ecological integrity assessment method for wetland ecosystems. Ecological Indicators 104:764-775.(natureserve.org/sites/default/files/publications/files/Faber-Langendoen etal_2019_NatureServe EIA method for wetland ecosystems_EcoInd.pdf, as of 2024)
Kodero, J.M., B.S. Felzer, and Y. Shi. 2024. Future transition from forests to shrublands and grasslands in the western United States is expected to reduce carbon storage. Communications Earth and Environment 5:78-88. doi.org/10.1038/s4-3247-024-01253-6 (nature.com/articles/s43247-024-01253-6, as of 2024)
Mack, J.J. 2001. Ohio Rapid Assessment Method for Wetlands, version 5.0: User’s Manual and Scoring Forms. Ohio EPA Technical Report WET/2001-1, Ohio Environmental Protection Agency, Division of Surface Water, Columbus. 86 pp. (dam.assets.ohio.gov/image/upload/epa.ohio.gov/Portals/35/401/ORAM%20Manual%205.0.pdf, as of 2024)
NatureServe, Ecological Integrity Assessment (natureserve.org/products/ecological-integrity-assessment, as of 2024)
Penn Pilot Historical Aerial Photos of Pennsylvania (arcgis.com/apps/View/index.html?appid=10af5f75f9f94f01866359ba398cb6a9, as of 2024)
Pennsylvania Landscape Condition Model (LCM) (researchgate.net/publication/324569897_A_Landscape_Condition_Model_LCM_for_Pennsylvania, as of 2024)
Pennsylvania Natural Heritage Program, Pennsylvania Community Prediction Tool for Site Restoration (naturalheritage.state.pa.us/RestorationTool.aspx, as of 2024)
Pennsylvania Terrestrial and Palustrine Community Classification 2nd edition. (naturalheritage.state.pa.us/Communities.aspx , as of 2024.)
Pennsylvania Wildlife Action Plan, Conservation Opportunities Areas Tool (wildlifeactionmap.pa.gov, as of 2024)
Sweeney, B.W. and C.L. Dow. 2019. Riparian and upland afforestation: improving success by excluding deer from small areas with low fencing. Natural Areas Journal 39:90-107. doi.org/10.3375/043.039.0107 (stroudcenter.org/wp-content/uploads/SweeneyDow-2019-low-deer-fencing-NAJ.pdf, as of 2024)
Tracey, C. et al. 2016. A Landscape Condition Model (LCM) for Pennsylvania. Pennsylvania Natural Heritage Program, Pittsburgh. (researchgate.net/publication/324569897_A_Landscape_Condition_Model_LCM_for_Pennsylvania, as of 2024).
U.S. Forest Service: Gypchek—the Gypsy Moth Virus Product (fs.usda.gov/foresthealth/pesticide/pdfs/gypchek1_hqp.pdf, as of 2024)