Habitat description
Northern hardwood and conifer forests are associated with higher elevations, northerly latitudes, and cool, moist microclimate of the Berkshire Plateau, Worcester Plateau, and Taconic Ridge. Tree species include American beech, yellow birch, and sugar maple, and coniferous species, such as red spruce and balsam fir. Northern red oak also appears in some transitional northern hardwood forests.
Characteristic natural communities
Northern hardwood and conifer forests include several distinct natural communities ranging from fairly widespread northern hardwoods–hemlock–white pine forest and red oak–sugar maple transition forest, to more restricted high elevation spruce–fir forest.
Learn more about the natural communities found in dry woodlands and barrens:
- High elevation spruce–fir forest /woodland (S1)
- Hemlock forest (S4)
- Red oak–sugar maple transition forest (S4)
- Spruce–fir–northern hardwood forest (S4)
- Northern hardwoods–hemlock–white pine forest (S5)
- Successional northern hardwood forest (S5)
Natural communities are given state rarity/imperilment ranks ranging from S1-S5 (S1: rarest/most imperiled)
Characteristic plants and animals
Species of greatest conservation need (SGCN), such as the Jefferson salamander, blackpoll warbler, ski-tipped emerald dragonfly, and the early hairstreak butterfly rely on one or more of the natural communities in the northern hardwood–conifer habitat type. Black bear, bobcat, moose, several bat species, and nesting forest interior birds use this and other forested habitat types regularly. State-listed rare plants include dwarf rattlesnake plantain, black-fruited woodrush, showy orchid, and large-leaved goldenrod.
Associated habitats
Due to infrequent natural disturbance events, northern hardwood and conifer forests support some of the best examples of mature forest in the state. However, past extractive timber harvesting without long-term silviculture (often called “high-grading”) has degraded many northern hardwood and conifer forests, resulting in successional forests that would often benefit from active restoration. Young forest habitat is sometimes established in stands with shade intolerant northern hardwood tree species, such as aspen and paper birch. If allowed to mature undisturbed, young forest will develop into intermediate-aged and eventually mature northern hardwood and conifer forest. A variety of wetland and aquatic habitats including forest swamps and seeps, vernal pools, and steep cold streams often occur within northern hardwood and conifer forests.
Ecological processes
High elevations, northern latitudes, north-facing slopes, and acidic bedrock and soils limit the species of trees and other vegetation that can successfully survive and reproduce in some portions of Massachusetts. This leads to forests dominated by combinations of certain conifer and hardwood trees. Northern hardwood species range from pioneer, shade-intolerant species, such as quaking aspen, to shade-tolerant species, like sugar maple. In northern hardwood forests dominated by shade-tolerant American beech, yellow birch, and sugar maple, the combination of deep shade, moist soils, and less-flammable leaves results in wildfire return intervals of centuries to millennia. Natural disturbances leading to forest age diversity include ice damage, hurricanes, tornados, other severe storms, and insect outbreaks.
Threats
Development for residential and other purposes results in forest loss and fragmentation.
Invasive species of plants and insects also pose a significant threat. Japanese barberry and glossy buckthorn can dominate the understory shrub layer, limiting tree regeneration and reducing herb and shrub diversity. Hardy kiwi, a vine that can kill canopy trees, is an emerging threat in some locales. Hemlock wooly adelgid, emerald ash borer, and Asian long-horned beetle impact tree species common in northern hardwood and conifer forests, and these stressors interact with the climate change impacts detailed below. Invasive earthworms increase nutrient cycling and loss of forest floor organic material, which reduces or prevents the regeneration of many native plant species in mature forest, to the benefit of invasive exotic plant species.
Over-browsing by white-tailed deer result in natural system modifications that are hindering forest health and regeneration. High white-tailed deer abundance and herbivory can have a significant negative impact on the biodiversity of native herbs, tree seedlings and sprouts, and has been shown to also impact forest-breeding birds.
Climate change: Predicted increases in summer temperature, fall droughts, and winter freeze-thaw cycles are expected to increase stress on many high-elevation/northern-latitude tree species. This is likely to impact the stability of northern hardwood and conifer forests and may lead to changes in species composition. Increases in drought may increase frequency, severity, and extent of wildfire in this habitat type.
Conservation actions
- Proactive habitat protection. Protect northern hardwood and conifer forests 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. Policies related to sustainable forestry in privately owned forests may reduce the risk of forest loss and contribute to local economies.
- Conservation planning. Include key northern hardwood and conifer forests 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 northern hardwood and conifer forests and associated habitats in biodiversity conservation, flood mitigation, water filtering, and climate resiliency as part of broader communication strategies.
Restoration & management recommendations
The history of extractive timber harvesting with inadequate attention to biodiversity and species regeneration in many Massachusetts forests has altered their composition by preferentially removing tree species with high monetary value without making adequate preparation for regenerating those species. This history has also led to removal of many of the healthiest and fastest-growing individuals of harvested species, leaving behind poorly formed stems.
Planning phase
Before undertaking a project, it is important to complete a thorough planning process that establishes 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 how to benefit them;
- evaluate key threats, such as invasive species;
- secure key resources required to implement the project, including subsequent monitoring and adaptive management; and
- secure community, stakeholder, and institutional support.
If landowner goals include carbon sequestration or timber production, it is vital that the health and growth rate of the current forest be analyzed by a licensed forester before deciding on a management approach.
Management of habitat in northern hardwood and conifer forests should be planned at a landscape scale where possible, with attention given to several objectives: development of mature forests, restoration of species diversity in previously high-graded forests (subject to extractive timber harvesting without long-term silvicultural objectives), and maintenance of stands of multiple age classes across the landscape, including young forests. Dynamic Forest Restoration (Jones, 2022) is a developing method of combining mature forests with inclusions or adjacent forest stands of varying ages. This approach diversifies forest age classes and provides food and cover resources in younger stands for the benefit of a variety of species (for example, interior-forest-nesting birds that use open habitats during the post-fledging and pre-migration periods).
Management approaches
Management approaches will vary depending on landowner objectives and may range from: passive management; establishment of forest reserves; active management for forest health, carbon storage, or income from forest products; or creation of young forest habitat for conservation purposes. Landowners interested in mature forest may want to consider management and restoration actions to promote structural complexity and other old-growth or mature forest characteristics (D’Amato and Catanzaro, 2022)—especially in larger areas of northern hardwood and conifer forest that have not been recently cut. These approaches may help shift these forests towards old-growth or mature forest habitat characteristics, may maintain more carbon storage relative to traditional silviculture, and may provide some of the desired habitat characteristics earlier than in stands without such restoration. Passive management is another option that may ultimately restore old-growth characteristics, particularly in large, forested areas that are remote from development and other fragmenting features, such as roads. See mature forests for additional discussion and recommendations.
Timber stand improvement and other “pre-commercial” forms of tree cutting may be necessary in heavily degraded stands to regenerate a more diverse set of tree species. These practices should focus on retaining the healthiest and fastest-growing individuals of desired, as well as under-represented species as a source of natural seed. Silviculture in these degraded stands should also focus on creating the appropriate understory conditions for germination of this seed and subsequent survival of the seedlings, as well as associated native shrubs and forbs. In many cases, this will require patch openings, small group selection, individual tree selection, or other uneven-aged management techniques. Because the land-use history and environmental characteristics for these forests are so diverse, the involvement of a Massachusetts Licensed Forester is crucial for planning and undertaking this management.
Northern hardwood and conifer forests often include stands dominated by pioneering, shade-intolerant species, such as aspen (Populus spp.) and gray birch (Betula populifolia). Where overstory aspen trees occur, consider creating openings of five acres or more through even-aged management as part of a landscape-scale Dynamic Forest Restoration approach. Forest stands dominated by aspen provide important young forest habitat for numerous species of greatest conservation need in Massachusetts, including ruffed grouse. As aspen regenerates primarily clonally from root sprouts, even-aged silviculture favor this sub-type, as well as other pioneer tree species. As aspen species are relatively short-lived, without active management, these species will decrease in dominance across the landscape. See young forests for additional discussion and recommendations.
Addressing invasive species when managing northern hardwood and conifer forests is a priority—especially when actively managing forest habitat—as invasive plant species are often able to colonize and spread in response to increased light availability and soil disturbance. Evaluating and controlling established invasive species prior to forest management activities - and monitoring and treating invasives after tree removal has taken place—should aways be included in a management plan. Protocols to prevent the introduction or spread of invasive species during forest 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. Herbicide is usually required for effective control, particularly in areas with widespread infestations prior to the initial treatment and canopy thinning.
Additional resources
Find a Local Professional. This tool will allow you to find contact information for land trusts, foresters, estate planning professionals, and neighbors with conservation training working in your town. From UMassAmherst MassWoods. https://masswoods.org/professionals
D’Amato, Anthony and Paul Catanzaro. 2022. Restoring Old-Growth Characteristics to New England’s and New York’s Forests. Amherst: University of Massachusetts.
Fahey, Timothy J.; Reiners, William A. 1981. Fire in the forests of Maine and New Hampshire. Bulletin of the Torrey Botanical Club. 108: 362-373
Ford, Sarah E. and William S. Keaton. 2017. Enhanced carbon storage through management for old-growth characteristics in northern hardwood-conifer forests. Ecosphere 8:4. https://doi.org/10.1002/ecs2.1721
Hale CM, Frelich LE, Reich PB. Changes in hardwood forest understory plant communities in response to European earthworm invasions. Ecology. 2006 Jul;87(7):1637-49. doi: https://doi.org/10.1890/0012-9658(2006)87[1637:cihfup]2.0.co;2
Holdsworth AR, Frelich LE, Reich PB. 2007. Regional extent of an ecosystem engineer: earthworm invasion in northern hardwood forests. Ecol Appl. 2007 Sep;17(6):1666-77. doi: 10.1890/05-2003.1
Jones, Benjamin C. 2022. Dynamic Forest Restoration. RGS & AWS Magazine, Winter 2021.
Keeton, William. Managing for Old-Growth Structure in Northern Hardwood Forests.