Habitat description
Dry woodlands and barrens occur on dry nutrient poor soils and are often exposed to other harsh environmental conditions, such as salt-spray, wind, frost, and fire. The name “barrens” comes from European colonists who called any area that did not support large trees or productive farms “barrens.” Vegetation structure can range from a relatively open and sparsely vegetated woodland to an impenetrable thicket of scrub oak or pitch pine. Healthy barrens tend to burn frequently and consequently have more exposed soil, lower stature shrubs, and a more open canopy and midstory than do long unburned areas. The ground cover is often a mix of grasses, sedges, heaths, and forbs, many of which are specialized to the harsh environmental conditions. Open barrens may have scattered pitch pines and tree oaks, and with increasing tree density transition to open pitch pine, oak, or pitch pine - oak woodland. Frost bottoms are special features that occur in depressions where vegetation and topography cause extreme high and low temperatures, often freezing into the early summer, which limits the growth of trees. These unique plant communities harbor uncommon species, such as wood lily, creeping cherry, and other rare plants.
Dry woodlands and barrens are highly disturbance dependent communities and were historically associated with frequent fire. High quality examples of these communities are now rare and represent important conservation resources that provide habitat for a diverse suite of specialized and often rare and threatened animals and plants.
Characteristic natural communities
In the Massachusetts habitat classification, dry barrens and woodlands include several specific natural communities varying from open shrubland to woodlands with more tree canopy. These natural communities typically occur on sand and gravel glacial outwash, while the ridgetop community occurs on shallow acidic soils over bedrock.
Learn more about the natural communities found in dry woodlands and barrens:
- Pitch pine–scrub oak community (S2)
- Ridgetop pitch pine–scrub oak community (S2)
- Scrub oak shrubland (S2)
- Pitch pine–oak forest/woodland (S4)
Natural communities are given state rarity/imperilment ranks ranging from S1-S5 (S1: rarest/most imperiled).
Characteristic species
Key indicators of these communities are a dominant presence of scrub oak (two species), pitch pine, huckleberry, and lowbush blueberry (two species). Other shrubs frequently include bayberry, sheep laurel, teaberry, and bearberry. Other commonly found plants include Pennsylvania sedge, little blue stem, stiff aster, and yellow wild indigo.
Dry barrens and woodlands are habitat for many specialized and often rare animals in Massachusetts. State-listed species or other Species of Greatest Conservation Need (SGCN) include the New England cottontail, reptiles such as the eastern hog-nosed snake, birds, such as the eastern whip-poor-will and northern harrier, and insects, such as the barrens tiger beetle, and more than a dozen species of moths and butterflies, including the buck moth and frosted elfin butterfly.
View a complete list of Species of Greatest Conservation Need associated with this habitat.
Associated habitats
Dry barrens and woodlands are often found in association with and intergrade into dry grasslands and heathlands, coastal beaches and dunes, and maritime forests and shrublands. This habitat, including ridgetop occurrences, also occur in association with other forest habitats, such as oak forests and woodlands. Important wetland and aquatic habitats associated with barrens landscapes include coastal plain pondshores and acidic peatlands, such as Atlantic white cedar swamps.
Within dry woodlands and barrens, there can be mature areas that have “maturing and old-growth characteristics.” These mature woodlands are typified by older and larger trees of varying density, but where periodic fire reduces litter accumulation, maintains sandy mineral soils, and regularly resets the composition and structure of understory vegetation.
Ecological processes
Drought prone soils and fire or other disturbance—and the interaction of these factors—determine the presence and persistence of dry barrens and woodlands. However, harsh soil conditions alone are not always enough to ensure persistence. Without regular fire or other disturbance, in all but the driest soils, organic nutrients and moisture from decomposing vegetation will accumulate in the soil over time, facilitating the establishment and eventual dominance of species like white pine, aspen, and red maple. In the driest and most nutrient-poor soils, leaves and needles build up a deep fuel bed as highly flammable shrubs and pines grow dense. When too much dry vegetation accumulates, dangerous wildfires can occur.
Frequent disturbances, such as wood cutting, grazing, and most importantly fire, historically maintained the open structure and characteristic composition of dry barrens and woodlands. Along the coast, salt spray helps to maintain these communities, as does wind and ice on ridges, and growing season frost on glacial outwash plains, particularly in frost bottoms.
Threats
The primary threat is absence or suppression of disturbance such as fire, and lack of habitat management (natural systems modification). Development threatens this habitat directly through destruction and fragmentation, and indirectly by reducing the ability of managers to apply prescribed fire because of concerns about smoke impacts. Invasive species (plants and insects) pose an ongoing risk, as does damage by off-road vehicles (human disturbance).
Climate change: Dry barrens and woodlands have mixed prospects under climate models that predict increased drought. They could benefit because the dominant species of these communities are adapted to dry conditions, and competition from generalist species may be reduced by drought. A drier climate, however, could exacerbate other threats and make management more difficult. Climate models that predict an increase in precipitation may be more problematic and require more frequent habitat management with prescribed fire, mechanical treatment, or both. Prescribed fire may be more difficult to utilize under both wetter and drier climate change scenarios because storm events are expected to be more extreme with large rainfalls and longer droughts in between, creating conditions that are not suitable for fire implementation. Furthermore, climate change is expected to enable northward expansion by pests and diseases from other southern regions. Warmer winter temperatures have allowed expansion of the southern pine beetle from its native range in the southeastern and mid-Atlantic states into the northeast. Infestations are expected to become widespread in Massachusetts over the next years with tens of thousands of acres of pitch pine ecosystems at high risk of impact. Under a climate change scenario of increased drought, spongy moth outbreaks may be more frequent, killing oaks while leaving other generalist species like white pine or red maple to replace them.
Conservation actions
- Proactive habitat protection. Protect dry woodlands and barrens in conjunction with other interconnected habitats to maintain healthy and resilient landscapes for people and biodiversity conservation. Prioritize sites supporting state-listed animals and plants and other SGCN, as well as other protection priorities identified in BioMap and other conservation planning tools (e.g., municipal open space plans).
- Habitat restoration and management. See recommendations below.
- Law and policy. Regulate and limit the impacts of development and other land use changes. Innovative approaches to incentivizing compatible development should be considered where applicable.
- Conservation planning. Include key dry woodlands and barrens in conservation planning efforts at multiple spatial scales. (See BioMap as an example.)
- Monitoring and research. Monitor the health and trends of SGCN populations, plant communities, and other wildlife. Monitor the effectiveness of habitat restoration efforts and conduct targeted research to improve habitat and population management.
- Public outreach. Include information about the role of dry woodlands and barrens and associated habitats in biodiversity conservation, flood mitigation, water filtering, and climate resiliency as part of broader communication strategies.
Restoration & management recommendations
Due to their importance to Species of Greatest Conservation Need and vulnerability to stressors, dry woodlands and barrens have been designated as very high priority (tier 1) for restoration and management. Before undertaking a project, it is important to establish clear goals that are compatible with site conditions. Factors to consider include identifying the resources required for restoration and long-term maintenance, and securing community, stakeholder, and institutional support. For more information, please see: Habitat Management Priorities and Planning.
Planning phase
Before undertaking a project, it is important to establish clear goals that are compatible with site conditions, as well as with other conservation goals that may be relevant to the site. For example, it is important to:
- identify unique and/or otherwise sensitive species and natural communities and evaluate how to benefit them;
- evaluate key threats, such as invasive species;
- secure key resources required to implement the project, as well as subsequent monitoring and adaptive management;
- and secure community, stakeholder, and institutional support.
It is also important to identify the resources required for restoration and long-term maintenance and secure community, stakeholder, and institutional support.
Large sites may have numerous barrens natural communities, while a small site may target one key plant community. Goals should be consistent with the vegetation present before restoration. Large areas of suppressed scrub oak may be indicative of pitch pine–scrub oak community, whereas expanses of lowbush blueberry or huckleberry may suggest pitch pine–oak woodlands or heathlands. Goals should be set for vegetation type and cover, including different layers (i.e., surface, shrubs, trees) and the amount of bare soil and should be consistent with the level of maintenance effort that can be supported. Because dry woodlands and barrens can take many forms and occur on a variety of soil conditions, it may be best to consult with an expert to help establish goals that will best fit your site and program. Understanding the expression and ecological condition of surrounding dry woodland and barren natural communities, underlying soils, disturbance history, and other factors is often an important first step in the planning process.
At a landscape scale, large areas of dry woodland and barrens are needed to support populations of animals that require expansive territories, such as whip-poor-wills and other birds, and to ensure that populations can replenish after disturbance events, such as disease, extreme weather, or wildfire. However, it is important to restore and manage both large and small remaining patches of this habitat, as small sites are often embedded within a matrix of associated habitats and facilitate the persistence and movement of species across the landscape. In addition, small patches of high-quality dry woodland and barrens can also be an important component of conservation planning for some Species of Greatest Conservation Need, especially rare and other highly specialized plants and invertebrates that don’t need large areas to persist.
Prior to management, the site should be evaluated by an experienced fire practitioner to determine feasibility of prescribed fire implementation. This should be done early because it may inform other parts of the planning process, such as tree cutting or other mechanical treatments. Overstory thinning or understory mowing may be required to reduce the chance of high fire behavior. Barrens can be managed without fire but will require more frequent mowing and other treatments. Also, planning should account for additional overstory mortality following tree cutting caused by blowdown because of reduced wind sheltering, increased insect damage (especially in pitch pines), and prescribed fire.
Initial restoration
The first step in restoration is to control invasive plants that may be released by disturbance and increased light exposure. If the overstory density and composition is close to meeting the goals, prescribed fire or understory mowing may be all that is required. For barrens in poor ecological condition, such as those with closed canopies and invasion by generalist species like white pine, selective tree removal in order to open the canopy, remove generalists, and encourage restoration of native shrubs, grasses and forbs is usually next. Tree retention should be based on the target natural community, typically focusing on retaining healthy tree oaks and or pitch-pine and removing generalist species, like white pine. Typically, in pitch pine-dominant systems, residual basal area should be less than 60 square feet per acre, and space between trees should be at least 30 feet to prevent southern pine beetle infestation and reduce the chance of crown fire. Managing for a more open canopy and exposing bare mineral soil will encourage heath, scrub oak, grasses, and other herbaceous plants, but will also allow shrubs and saplings to grow more quickly. Whole tree removal is preferred to mulching because whole tree leaves less organic material on the ground, which maintains barrens soil characteristics and facilitates prescribed fire implementation. Depressions that are, or once were, frost pockets should be identified as areas for total canopy removal because trees reduce the ability of frost to maintain the open habitat.
Following cutting, prescribed fire should ideally be applied as soon as vegetation conditions permit. Initial burn(s) should be conducted when project fuels, such as slash and chip piles, are moist (usually spring) to prevent problems with smolder and smoke management. Subsequent burns may be conducted in other seasons to reduce woody cover. In the initial stages of restoration, frequent fire is needed to prevent woody plants from dominating the site. Pitch pine seedlings usually establish easily in active restoration sites. The seeds require bare soil and an open canopy to germinate, so some level of control following burning, cutting, and/or mowing may be necessary in some cases.
Mowing and/or herbicide treatments may be required to control resprouting trees, shrubs, and invasive plants, as prescribed fire is not typically sufficient. Control of resprouting hardwood trees, such as red maple, aspen, beech, and, sometimes, oak, may, sometimes, require herbicide treatments. When resprouts are roughly between knee to head high, foliar herbicide can be applied. Trees larger than head high may need to be mowed, in which case, prescribed fire and/or herbicide application may be required after resprouting. Understory mowing may be necessary in the earlier stages of restoration but can have the undesirable effects of increasing soil moisture retention and causing smoldering during prescribed fire. Scrub oak can support extreme fire behavior, and mowing/mulching thickets over 6’ tall may be necessary prior to burning. When using a mulching head for vegetation management on a prescribed fire site, it is important that dull “hammer” teeth are used instead of sharp cutting teeth. The mowed product should appear shattered or shredded, like kindling, not fine chips, like mulch.
Bare soil is an important element of dry woodland and barren habitats that is needed to promote many characteristic plants and animals. Bare sand supports many uncommon ground nesting bees, rare beetles, and nesting areas for various reptiles. Heavy machinery and fire usually produce enough bare soil in a restoration site to engage the native seed bank as well as create habitat for species that need access to bare soil. In areas where fire is not an option, intentional soil disturbance may fill that role; however, any exposed soil with an open canopy and pitch pine nearby will probably become dominated by pitch pine seedlings. Areas of bare sand may take slightly longer to fill in with pitch pine than soil with some organic material. Maintaining discrete areas of exposed soil would eventually require some pitch pine control. Alternatively, small patches of soil disturbance could be abandoned and new areas established as the old ones are overtaken by young pitch pine. Soil disturbance should be a complementary practice on a small scale for specific objectives.
Maintenance
Prescribed fire should be the primary maintenance tool wherever possible. Barrens should generally burn every 2-10 years depending on site conditions and objectives. Less frequent fire may be acceptable in pitch pine–oak forests and woodlands, but long intervals can sometimes lead to invasion by white pine or high fire danger where flammable vegetation becomes too thick. To maximize effectiveness, burns should be conducted at different times of the year depending on specific site management objectives, rare species considerations, and land use history.
Spring fires are often used in early restoration because the project materials are moist and will not cause smolder problems. Spring burns also help warm season grasses establish. When burning early in the spring, prior to leaf out, fire behavior can be very high, especially in scrub oak, because there is little moisture in the leaves. Early spring burns also promote resprouting woody vegetation. Burning exclusively in the spring will likely cause a proliferation of woody plants that may end up a management problem requiring herbicide treatments or other interventions. Burning in late April to early May, at the time when foliar moisture content in pitch pines is low, can cause increased torching potential. Burning on warm spring days before leaf-out, usually in early May, can cause oak mortality. Burning during the summer and early fall can be challenging because dry dead fuels can smolder, and fire may not carry through areas with green growth. However, summer and early fall burns have the greatest impact on small trees and shrubs while causing significant reductions in the depth of leaf litter and duff. Summer and early fall burns can temporarily damage heath, which should be a consideration if goals include promoting blueberry or huckleberry.
Periodic understory mowing and/or herbicide treatments of trees and shrubs may be required if fire is not an option or does not achieve all the desired results. It is common for fire and other treatments to be needed in combination for long-term management and maintenance. Like the seasonal effects of burning, mowing has different impacts on vegetation depending on the time of year. Summer and early fall mowing tend to have a greater impact on reducing the vigor of resprouting trees and shrubs, while dormant season mowing will cause increased resprouting. Mowing helps to establish the desired structure and provides scarification for herbaceous plant regeneration; however, it also contributes to the buildup of organic material on the surface, which can facilitate the establishment of undesirable trees and shrubs.
The early detection and rapid treatment of invasive plants should be a priority. Because of the harsh conditions of barrens soils, there are usually fewer invasive plants than in moister and richer sites, but invasives can still be a management problem. Invasive plants often establish after mechanical treatments because seeds germinate in the exposed soil, increased light allows dormant plants to grow, and new invasive seeds come in on equipment. Fire can be helpful for discouraging some invasive plants, but usually herbicide is required for treating widespread invasive plant infestations. Evaluating and controlling established invasive species prior to management activities - and monitoring and treating invasives after management has taken place - should aways be included in a management plan. Protocols to prevent the introduction or spread of invasive species during management, such controlling potential vectors (contaminated soil, equipment, etc.) by powerwashing equipment prior to arriving on site, should be implemented to the greatest extent practicable. Finally, regular monitoring and rapid response to pioneering invasive species before they begin to impact habitat should be a priority.
In particular, southern pine beetle monitoring can help with early detection of infestations, allowing for quick action. In large pitch pine systems, pheromone traps can help monitor population levels and can pick up infestations in the early expansion phase. Without trapping, managers should look out for groups of pitch pines with browning needles. Popcorn-like pitch tubes at eye level and above can indicate southern pine beetle attack. If an infestation is found, contact the Department of Conservation and Recreation's Forest Health Program, and consider pursuing suppression activities.
Examples
- Myles Standish Complex Pine Barrens Restoration: Ongoing restoration project at Myles Standish State Forest and conjoining Wildlife Management Areas to restore pine barrens.
- Massachusetts Army National Guard Camp Edwards Natural Resources Program: Camp Edwards contains the largest intact pine barrens in the Commonwealth. The base has examples of pitch pine – oak forests and woodlands, pitch pine – scrub oak community, scrub oak shrublands, sandplain grasslands, and is home to many rare plants and animals.
- Montague Plains WMA barrens restoration is one of the best examples in New England and contains several uncommon plant and animal species.
- Sudbury Valley Trustees Desert Natural Area: Recent pine barrens project in the early phases of restoration.
- Muddy Brook WMA barrens restoration includes a patchwork of pitch pine–oak woodlands, oak woodlands, heathlands, and grasslands. Since restoration efforts began, the diversity of plants and animals, especially insects, has increased dramatically.
- West Barnstable Conservation Area: Town conservation land on Cape Cod glacial moraine. The area is pitch pine–oak forests and woodlands. Portions have been managed with prescribed fire.