Habitat description
Barrens are habitats with vegetation adapted to harsh environmental conditions such as dry nutrient poor soils, salt-spray, wind, frost, and fire. In the Massachusetts habitat classification, the barrens term is more narrowly used to include several specific natural communities such as open woodlands, shrublands, and ridgetops. The Pitch Pine - Scrub Oak, Pitch Pine - Oak Woodland and Scrub Oak Shrubland communities typically occur on sand and gravel glacial outwash, and the Ridgetop Pitch Pine – Scrub Oak community occurs on shallow acidic soils over bedrock. The name “barrens” comes from European colonists who called any area that did not support large trees or productive farms “barrens”.
The structure of Barrens 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 (Pinus rigida) and tree oaks (Quercus spp.), and with increasing tree density transition to open pitch pine, oak, or pitch pine - oak woodland. Openings where trees are sparse grade into Sandplain Grasslands and Heathlands or Ridgetop Heathland. 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.
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.
Associated habitat types
Sandplain Heathland or Ridgetop Heathland and Sandplain Grassland communities typically occur within a larger matrix of Barrens. Pitch Pine - Oak Forest/Woodland is included in this habitat type because where fire or other disturbance is absent for a sufficient period of time or environmental conditions are somewhat less harsh, Barrens grade into Pitch Pine - Oak Forest/Woodland.
Characteristic communities and species
More information on the specific natural communities (Swain 2020) within this habitat type is available from the following fact sheets:
- Pitch Pine - Scrub Oak Community (S2)
- Pitch Pine - Oak Forest/Woodland (S4)
- Ridgetop Pitch Pine - Scrub Oak Community (S2)
- Scrub Oak Shrubland (S2)
Key indicators of these communities are a dominant presence of scrub oak (Quercus ilicifolia, Q. prinoides), pitch pine (Pinus rigida), huckleberry (Gaylussacia baccata), and lowbush blueberries (Vaccinium angustifolium and V. pallidum). Other shrubs frequently include bayberry (Morella pensylvanica), sheep laurel (Kalmia angustifolia), teaberry (Gaultheria procumbens), and bearberry (Arctostaphylos uva-ursi). Species commonly found in Barrens but that are not necessarily indicators include Pennsylvania sedge (Carex pennsylvanica), little blue stem (Schizachyrium scoparium), stiff aster (Ionactis linariifolia), and wild yellow indigo (baptisia tinctoria).
Barrens are habitat for many specialized and often rare animals in Massachusetts. Endangered, Threatened, and Special Concern species inhabiting Barrens include the New England Cottontail (Sylvilagus transitionalis), reptiles such as the Eastern Hog-nosed Snake (Heterodon platirhinos), birds such as the Eastern Whip-poor-will (Antrostomus vociferus) and Northern Harrier (Circus hudsonius), and insects such as the Barrens Tiger Beetle (Cicindela patruela), Purple Tiger Beetle (Cicindela purpurea), and more than a dozen species of moths and butterflies, including the Buck Moth (Hemileuca maia) and Frosted Elfin butterfly (Callophrys irus).
Ecological processes
Drought prone soils and fire or other disturbance - and the interaction of these factors - determine the presence and persistence of Barrens and associated natural communities. The dry and nutrient-poor, sandy or rocky soils are an essential foundation for Barrens because specialists such as scrub oak, pitch pine, heaths, and warm-season grasses thrive, while more widespread species (which may invade the community where moisture and nutrients are greater) fare poorly. However, harsh soil conditions alone are not always enough for Barrens to persist. Without regular fire or other disturbance, Barrens will take one of two pathways. 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 such as 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 Barrens. 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 to the persistence of Barrens is absence or suppression of disturbance such as fire, and lack of habitat management. Development threatens Barrens directly through destruction and fragmentation, and indirectly by reducing the ability of managers to apply prescribed fire because of concerns about smoke impacts. Invasive plants and insects pose an ongoing risk, as does damage by off-road vehicles.
- Climate Change: Barrens 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. Persistence of Barrens under 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 (Dentroctonus frontalis) from its native range in the southeastern and mid-Atlantic states into the Northeast, and it is expected to establish in Massachusetts soon. Pitch pine is particularly susceptible to the Southern Pine Beetle, and infested stands may be killed in a short period of time. Spongy Moth (Lymantria dispar formerly “Gypsy Moth”) severely impacts oaks during outbreaks, particularly during periods of drought. Under a climate change scenario of increased drought, spongy moth outbreaks may be more frequent, killing oaks while leaving other species to replace them.
Restoration & management recommendations
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.
At a landscape scale, large areas of 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 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 type. Small sites situated around and between large Barrens facilitate the movement of species (and genetics) and support the long-term persistence of obligate species across the landscape. Small patches of these communities are often remnants of much larger occurrences of important historic sites, and therefore have the potential to support rare obligates seldom found elsewhere.
- Planning Phase: Goals should be established for the site. If managing for a specific species or suite of species, the goals should match their habitat requirements. Some rare plants and animals prefer partial shade, while others demand sites with few or no trees. The site size and proximity to other Barrens may influence goals. Large sites may have numerous types of Barrens communities, while a small site may target one key plant community or build off nearby Barrens sites, expanding habitat size, providing a missing element, or linking sites for a certain species of concern. Goals need to 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. Goals need to match the level of maintenance effort that can be supported. Barrens management is often focused on controlling woody vegetation. Open habitats tend to require more frequent management actions, such as prescribed fire or mowing, than partially shaded habitats. Barrens sites that have not recently burned or experienced another disturbance are usually too densely covered with trees and include non-barrens species. To restore the overstory structure and composition tree cutting is normally part of the process. Because 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.
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. Harvest areas, skid roads, firebreaks, and burn units should be established in coordination to limit conflict and reduce overall cost. 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/or herbicide 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. Mortality is highly variable and depends on soil type, region, topographic position, residual tree density, and the timing of weather events like high winds and droughts. Generally, the drier the site, the warmer the region, and the fewer trees left behind, the higher the mortality rate. Some mortality may be reduced by delaying harvest and fire during drought or insect/disease outbreaks and limiting pitch pine cutting to winter months when insect activity is low. - Initial Restoration: The first step in restoration is to control invasive species that may be released by disturbance and increased light exposure. In overgrown Barrens, overstory thinning is usually next. Tree retention should be based on the target natural community. Species such as white pine, red maple, aspen, birch, beech, and cherry should be targeted for cutting as the overstory thinned to the desired cover. In all pitch pine-dominant systems residual basal area should be less than 80 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. Cutting more heavily 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. If the overstory density and composition is close to meeting the goals, prescribed fire or understory mowing may be all that is required. 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 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. Following burning, cutting and/or mowing, pitch pine tend to grow in high numbers, and are more likely to be too dense than too few.
Mowing and/or herbicide treatments may be required to control resprouting trees, shrubs, and invasive plants. Control of resprouting hardwood trees such as red maple, aspen, beech, and sometimes oak will likely require one or more herbicide treatments to kill the underground portions of the target trees. Foliar herbicide treatments should be done when resprouts are roughly between knee high and head high. Trees larger than head high may need to be mowed, in which case they will probably have to be sprayed after resprouting. Mowing can be necessary for “resetting” structure, but can have undesirable side-effects of increasing moisture retention in soil and causing smolder problems for prescribed fire. Excessive pitch pine regeneration can become problematic in open canopy Barrens, especially where soil is heavily disturbed. Herbicide treatments may be needed to kill seeding/sapling pitch pines and prevent the formation of overly dense stands. Dense stands of pitch pine are a fire danger and shade out desirable vegetation. 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 Barrens habitats which is needed to promote many characteristic plants and animals. Bare sand is an important type of bare soil that supports ground nesting bees, rare beetles, and nesting areas for various reptiles. Heavy machinery and fire usually produce more than enough bare soil in a restoration site. 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 to 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 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.
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: Restoration site for inland pine barrens. One of the best examples in New England. 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: A patchwork of pitch pine – oak woodlands, oak woodlands, heathlands, and grasslands. Since the restoration has begun, 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.
Additional resources
- Coming soon