Northern Hardwood Forests
The 2015 North Carolina Wildlife Action Plan defines 41 priority habitats for the state. More information about this habitat can be found in Section 4.4.3.
Contents
Habitat Priorities
Surveys
- Fill in distribution gaps for Carolina Northern Flying Squirrel. Continue survey work on distributions within and between known populations. (Surveys Priority)
- Obtain baseline data on SGCN and priority species, especially species that depend on high-elevation forests. (Surveys Priority)
- Conduct shrew surveys to determine the distribution of Long-tailed, Pygmy, and Water shrews and surveys to document the response of shrews to disturbance/management. (Surveys Priority)
- Conduct surveys for rare salamanders like Weller's, Northern and Southern Pygmy, Seepage, and Tellico, as well as more common species such as Ravine Salamanders, to determine their actual distribution and better define their habitat associations. (Surveys Priority)
Monitoring
- Establish monitoring systems and protocols and implement programs to monitor population trends for all high-elevation species.
- Develop and implement monitoring systems and protocols for population trends for all high-elevation species, including those associated with northern hardwood forest, with top priority toward rare species and secondary priority toward all species occurring in this relatively rare community of the North Carolina landscape.
- Establish more Monitoring Avian Productivity and Survivorship (MAPS) stations, point counts, and migration banding stations; montane birds are not adequately picked up in BBS routes.
Research
- Conduct genetic studies across taxonomic groups to assess degree of population isolation/gene flow and determine taxonomic status (primarily bird taxa thought to be southern Appalachian endemics).
- Initiate habitat use studies for many species to assess use of microhabitats, forest age classes, and habitat spatial relationships.
- Conduct research on habitat management techniques to successfully establish mixed spruce–northern hardwood stands in non-forested areas or appropriate pure/young northern hardwood stands.
- Research phenological relationships of priority species to better understand how changing climate conditions will affect seasonal availability of food resources.
Management Practices
- Consider and implement silvicultural management at appropriate locations to enhance understory development, provide regeneration and habitat for disturbance-dependent species or early successional species, such as Golden-winged Warbler, and enhance mature forest conditions in young to middle-aged pure stands.
- Expand management of existing northern hardwood forests and adjacent habitats (particularly spruce–fir forests) to ensure the complete mix of age class, composition, and conditions necessary to sustain populations of a wide range of species that utilize this community.
Conservation Programs and Partnerships
Description
Northern hardwood forests are found on high mountain slopes with a cool climate and high levels of rainfall in western North Carolina and are concentrated in many of the same high-elevation areas as spruce–fir forests. The name refers to the resemblance of these forests to those in the northeastern United States, which have similar canopies, but the presence of southern Appalachian endemic species makes the community types in North Carolina different from those in the north. High-elevation climate, slope, aspect, and past disturbance are critical ecological determinants of the distribution of northern hardwood forests today. In general, they are widespread throughout the region owing to their lower elevation range.
Northern hardwood forests are dominated by combinations of moist-site hardwoods such as Yellow Birch, beech, Yellow Buckeye, and Sugar Maple. The herb layer is often lush, and may range from low to fairly high diversity. These forests are subject to periodic widespread disturbances, such as ice storms or severe winds, which provide canopy openings, but probably seldom or never remove the whole canopy at once.
Three recognized variants of this community type are determined primarily by topography and soil chemistry: boulderfield forest, beech-gap, and typic subtypes.
- In the boulderfield forest, Ice Age freeze–thaw processes have left the ground completely covered with large boulders with very little soil. These areas are dominated by Yellow Birch with a distinctive undergrowth of gooseberries and moss on the rocks.
- The beech gap subtype occurs in high-elevation gaps and peaks, where beech trees stunted by the wind predominate. In the most extreme cases, the tree canopy may be reduced to shrub size. The trees may be quite old, although small, as growth and reproduction are relatively slow.
- The typic subtype varies in composition and diversity. Some have a lawn-like ground cover of just a few species of sedges and grasses, while others have a lush and diverse herb layer.
While the northern hardwood habitat can be defined in general terms, ecologically, it should be considered in association with spruce–fir forest for the purposes of maintaining ecological relationships and sustainability. Often components of spruce–fir habitats are present in sub-dominant numbers within northern hardwood communities, and increase in dominance along the elevation gradient to a point where spruce–fir becomes the dominant community.
The 2005 WAP described Southern Blue Ridge Mountain northern hardwoods as a priority habitat (see Chapter 5) (NCWRC 2005).
Location of Habitat
Northern hardwood forests are found throughout western North Carolina on high-elevation sites with abundant rainfall and a cool climate. Generally these conditions occur above 4,000 feet, but more often it is above 4,500 feet. The majority of northern hardwood forests are on public lands and many are in protected status. Significant amounts of northern hardwood forest occur on federally owned lands including US Forest Service (Pisgah and Nantahala National Forests) and National Park Service lands (Blue Ridge Parkway and Great Smoky Mountains National Park), in the Great Smoky Mountains, Great Balsams, Plott Balsams, Black/Craggy Mountains, Unicoi Mountains, and in the vicinities of Roan Mountain and Grandfather Mountain. While most of the available northern hardwood forest is associated with these high-elevation mountain ranges, significant amounts are present in other areas of suitable elevation throughout the region, such as in the Amphibolite Mountains in Ashe and Watauga counties. A small percentage does occur on state-owned lands, and other conservation ownerships (e.g., The Nature Conservancy, local land trusts, etc.).
Problems Affecting Habitats
Development pressure includes threats from a large increase in second homes and recreation facilities. Many nonnative pathogens are a potential problem for several tree species in this ecosystem, including the Hemlock Woolly Adelgid, Balsam Woolly Adelgid, Gypsy Moth, Emerald Ash Borer, and beech scale. The isolated nature of several populations of wildlife, such as the Carolina Northern Flying Squirrel, Northern Saw-whet Owl, Black-capped Chickadee and Weller’s Salamander, is likely detrimental to the genetic flow and overall long-range health of the species.
Many of the former fir forests and logged or grazed areas are regenerating into northern hardwood stands, without a conifer component (spruce or fir). Development on private lands, and logging on private and some public lands remain threats, and are likely the most immediate and greatest threats to a significant number of good examples. Climate change, particularly associated drought and wildfire, is the greatest threat to protected examples. However, the threat of climate change is less severe than in spruce–fir forests and the threat of logging and development are relatively greater.
The aging of many northern hardwood stands has resulted in closed canopy conditions and decreasing habitat for bird species that rely on diverse understory development, such as the Canada Warbler. Lack of disturbance has reduced available habitat for disturbance-dependent species such as the Golden-winged Warbler and Yellow-bellied Sapsucker (Hunter et al. 2001a). In turn, the impacts to other wildlife from stand-level disturbance will need to be examined. For example, small mammals in the family Soricidae, such as Masked and Smoky shrews, can respond favorably to forest disturbance in northern hardwoods (Ford et al. 2002), but this may not be true for other small mammals or salamanders.
Climate Change Compared to Other Threats
Comparing climate change to other ecosystem threats can help define shortand long-term conservation actions and recommendations. The effect of a changed climate is likely to vary widely among examples of these communities, depending on topographic sheltering, configuration of rocks, soil depth, size of groundwater pools, and amount of overland runoff. These systems are tied to specialized small environments and will be unable to migrate as the climate changes. Many may change very little, while a few will shrink, will be disturbed by wind or flood, or will change substantially because of temperature changes or drought. A small net loss of acreage may occur, but more seeps may be temporarily affected by drought.
Impacts to Wildlife
Northern hardwood forests provide habitat for numerous wildlife species that also rely heavily on spruce–fir forests. Because of the spatial relationship between them, and the fact that they share many ecological components and plant species, northern hardwood forests are critical to maintaining many species of birds and mammals dependent upon spruce–fir habitats. In addition, northern hardwood plant species may be critical components of spruce–fir habitats even in their sub-dominant role. Consider, for example, the fact that many spruce–fir dependent wildlife species are cavity nesters. Yellow Birch, beech, Sugar Maple, and Buckeye often provide more natural cavities and decaying wood than spruce or fir for species such as Northern Flying Squirrels, Yellow-bellied Sapsuckers, Black-capped Chickadees, Northern Saw-whet Owls, and other wildlife.
There is a major concern about salamanders, as this is a key ecosystem group for rare and southern Appalachian endemic species. On the other hand, the bird species are all more common and widespread farther northward, though a few species may become rare in the state. The aging of many northern hardwood stands has resulted in closed canopy conditions and decreasing habitat for bird species that rely on diverse understory development, such as the Canada Warbler.
At least six taxa are endemic to northern hardwood forests in the southern Appalachians; three others may also fall in this category, but have not yet been formally described as separate subspecies. Additionally, one moth appears to be a major disjunct from the northern Appalachians and several others are likely to have a similar distribution but are presently too poorly known. All species listed for this ecosystem group are likely to be strongly affected by climate change, as well as the effects of increased fragmentation.