Oak and Mixed Hardwood/Pine Forests and Managed Timber
The 2015 North Carolina Wildlife Action Plan defines 41 priority habitats for the state. More information about this habitat can be found in Section 4.4.11.
Contents
Habitat Priorities
Surveys
- Conduct surveys to document priority and common species in areas poised for development (edge of urban expansion) to establish baseline populations and identify problems before development expands. (Surveys Priority)
- Determine the current baseline distribution and status of species mainly associated with oak and mixed hardwood/pine forests (especially those that are state-listed or believed to be declining) for which that information is lacking. (Surveys Priority)
Monitoring
- Initiate long-term monitoring for breeding neotropical migrants (especially ground-nesters and cavity-nesters), bats and small mammals (e.g., moles, shrews, rodents), amphibians that use woody debris as a microhabitat, and Timber Rattlesnakes and other secretive reptiles.
- Monitor tree infestations and diseases to document potentially destructive organisms shortly after they show up, while there is still a chance to contain or eradicate the pest.
- Develop standardized monitoring programs analogous to the Breeding Bird Survey for reptiles, amphibians and small mammals. Of particular interest is trend information for those species dependent upon snags and woody debris.
Research
- Research and identify important wildlife crossing areas; evaluate connectivity issues between intact and fragmented habitats used by priority species; work with partners to improve crossing and connectivity.
- Conduct long-term and large-scale replicated studies that have controlled experimental approaches and that focus on population demographics and the response of species to habitat manipulations, where appropriate, for oak/mixed hardwoods forest taxa including birds, bats, small mammals, amphibians, and reptiles.
Management Practices
- Create transportation facilities that utilize longer bridges at streams and wetlands to minimize impacts (and thereby reduce mitigation requirements) and provide crossing options for wildlife that often travel these riparian corridors and disperse to upland communities.
- Work with adjacent states on mutual planning and conservation for regional species concerns, especially since some priority species are likely to expand their range due to climate change impacts.
- Control invasive species in the short run, while populations are relatively limited and small, to prevent greater damage by them in the future.
- Use infrequent prescribed fire and canopy gap management to improve forest structural heterogeneity (frequent fire will limit shrub and understory development necessary to breeding bird species).
- Manage and protect mixed hardwoods/pine to promote future large, unfragmented tracts. This is especially important for amphibians, reptiles, small mammals, and bats.
- Target invasive and exotic species control at ecologically sensitive areas and at new and potentially manageable outbreaks.
Conservation Programs and Partnerships
Description
This ecosystem has an oak or mixed hardwood/pine component and occurs on both xeric and mesic sites, in the Piedmont and Coastal Plain ecoregions. (Oak and pine forests in the Mountains are covered in other sections in this chapter.) Oak forests were once the most common natural community type in the Piedmont ecoregion, occurring over most of the uplands. In the Sandhills and Coastal Plain ecoregions, they were much more limited, occurring primarily in dissected areas near streams. They also range across topographic gradients from the Piedmont to some of the highest Mountain ranges.
The following communities are present within this ecosystem; dry oak–hickory forest, dry-mesic oak–hickory forest, basic oak–hickory forest, xeric hardpan forest, and Piedmont monadnock forest (Schafale and Weakley 1990).
- Dry–mesic oak–hickory forest and dry oak–hickory forest are the most typical of the five community types, occurring on upland slopes and ridgetops on acidic soils. White Oak is usually the most abundant tree in both. Post Oak and Southern Red Oaks are the primary associates in dry oak–hickory forests and Northern Red Oak and Black Oak in dry–mesic oak–hickory forests.
- Piedmont monadnock forests, typically dominated by Chestnut Oak and Scarlet Oak, occur on scattered hills, which are resistant to the erosion affecting the surrounding land.
- Basic oak–hickory forests occur on upland flats and slopes in sites similar to dry and dry-mesic oak–hickory forests, but with soils that are not acidic. Most of the soils are apparently near neutral pH rather than truly basic and usually occur over mafic rocks such as gabbro and diabase. They are dominated by White Oak in combination with Post Oak or Black Oak, and a number of understory, shrub, and herb species that are scarce or absent on acidic soils are present.
- Xeric hardpan forests are the most distinctive of the Piedmont and Coastal Plain oak forests. They occur on flat to gently sloping uplands with clay hardpans that restrict water and root penetration. This situation is most common on mafic rocks, but it also occurs on acidic shales. These sites may have shallow standing water in wet seasons, but are extremely dry in dry seasons. The canopy is dominated by some of the most drought-tolerant species in the state, Post Oak and Blackjack Oak, and is often somewhat open.
In addition to these natural communities, there are numerous acres of managed pine plantations, primarily of Loblolly and Shortleaf pines, as well as successional stands of these pines scattered across North Carolina (Huang et al. 2015). Successional communities, which may have a pine stand component, are addressed in Section 4.4.17 in this chapter. Managed stands may be thinned to reduce overcrowding, subjected to prescribed fire to reduce fuel for wildfires, or herbicide applied to control insect or disease attacks. Scientific literature provides evidence that intensively managed Loblolly Pine stands can provide a diverse herbaceous plant community throughout a significant portion of a plantation’s rotation that benefits conservation of biological diversity (e.g., Wigley et al. 2000; Loehle et al. 2005; Miller et al. 2009; Homyack et al. 2014), including species of special concern (Miller 2003; Duchamp et al. 2007; Wigley et al. 2007; Morris et al. 2010; O’Bryan 2014; Bender et al. 2015; Johnson 2015). Intensively managed pine forests may contain a diversity of habitat types and conditions, depending on different ages of intensively managed stands, different silvicultural treatments, presence of non-intensively managed stands, such as natural stands and riparian buffers, non-forested areas, and the interaction of these habitat conditions across the landscape (Wigley et al. 2000; Jones et al. 2008; Miller et al. 2009; Morris et al. 2010).
The Mid-Atlantic Coastal Plain ecoregion and Piedmont ecoregion oak forest (including mixed hardwoods and pine), another description for this community, is described in the 2005 WAP (see Chapter 5) (NCWRC 2005).
Location of Habitat
Mature hardwood and pine forests are found throughout the Piedmont ecoregion, though the total acreage has been declining in recent years. High-quality examples of oak forests in the Piedmont can be found on public lands such as Caswell Game Land, Umstead State Park, and Uwharrie National Forest. Examples of large size and good quality oak-dominated communities are now lacking in the Coastal Plain.
Problems Affecting Habitats
Many of the problems impacting oak and mixed hardwood/pine forests, including fire suppression and even-aged forest management, result in a loss of habitat complexity and associated wildlife niches (Hunter et al. 2001a). Most Piedmont forests have been logged or cleared at least once within the past 300 years, and many have been cut multiple times. The quality of existing tracts ranges widely across the Piedmont and depends primarily upon the age of the canopy trees, management history, and size of the tract (Godfrey 1997). Some native forest stands are being replaced by even-aged pine plantations, resulting in decreased habitat value for forest species that rely on diverse forest composition and structure, such as Kentucky Warbler and Wood Thrush. Pine plantations do, however, provide increased opportunity to provide habitat for Brown-headed Nuthatch and Northern Bobwhite Quail, with proper management.
Sudden oak death disease, which was detected at plant nurseries within North Carolina in 2004, could potentially have devastating impacts on oak forests across the state.
North Carolina is a major timber producer, with an estimated average 23.2 million cubic meters of wood products produced annually (Huang et al. 2015). Shorter rotation forestry limits the creation of old-growth forest dynamics, such as creation of canopy gaps, hollow trees, snags, and woody debris. In 2002, less than 1% of both hardwood and pine trees in the Piedmont measured greater than 19 inches diameter at breast height (Brown and Sheffield 2003), indicating that there are few old, large trees that help provide these old growth conditions. It should be noted, however, that tree diameter does not always correlate with tree age. Older stands will be more likely to be established and maintained on public land than on commercial forestland, though niche markets for larger timber may entice some landowners to extend cutting rotations.
An increase in hurricanes or other severe storms may increase wind damage in forests. These effects are likely to be localized. Small scale wind disturbances can create canopy gaps, downed woody debris, and patches of early successional habitat which can be beneficial to both early successional and mature forest species. Large scale wind disturbances will benefit early successional species but will harm mature forest species.
Lack of fire is leading to slow changes in composition, including reduced oak regeneration. In spite of benefits from fire, there is a need to control wildfires in drought conditions, to prevent intense fires, and to prevent whole patches of fragmented forest from being burned at the same time. Low intensity fires would be beneficial, but intense wildfires would be destructive. Increased prescribed burning will produce a more open canopy, reduced understory, increased herb cover with more grasses, and longer lasting canopy gaps.
Direct effects of the warmer climate on these communities are likely to be limited. Similar oak forests range well to the south of North Carolina where normal temperatures are higher. The most severe droughts and hot spells of recent record have had only limited effects on them. They can occupy some of the driest places on the Piedmont landscape. Increased drought may possibly favor oaks, but increased wind damage favors the understory species. If drought leads to severe wildfires, it would be harmful to oak forests, but the ease with which fires may usually be controlled in them makes this unlikely.
Climate Change Compared to Other Threats
Comparing climate change to other ecosystem threats can help define shortand long-term conservation actions and recommendations. While climate change is a significant concern for these communities, several other threats are more severe and may be a more immediate threat. Both the extensive examples in the Piedmont and the more limited range in the Coastal Plain continue to be rapidly destroyed by ongoing urban, suburban, rural, residential and commercial development. Continued population growth makes this the most severe threat, in the current and the future climate. However, the fragmentation and loss of extent caused by it will increase the alteration caused by climate change, as isolated communities are unable to migrate and species are unable to move to more favorable sites.
Impacts to Wildlife
Development causes direct loss of forest habitat and also fragments remaining forested patches. Fragmentation of forests into smaller contiguous blocks is a concern for forest interior birds (like Wood Thrush and Hooded Warbler), which may occur in lower densities or suffer lower productivity or survival in small habitat patches. Animals with large home ranges or dispersal needs may become isolated or absent in small tracts. Fragmentation by roads and development can be particularly problematic for reptiles (particularly Timber Rattlesnake).
Historical data suggests that oak communities benefited from periodic fires (Abrams 1992; Close 1996), and many oak species are fire tolerant. In pine stands, fire can play a very important role in reducing the midstory while enhancing structure in the understory. Fire helps to create snags, woody debris, and canopy gaps, and prepares a fertile seed bed, while also improving vegetative structure. The benefit of fire to understory plant development is highly dependent upon the density of canopy trees, with closed-canopy stands suppressing the growth of grasses and forbs following fire. Cavity-nesting birds, arboreal mammals, and some frogs, lizards, and snakes are impacted by the lack of snags, while reptiles, amphibians, and small mammals are impacted by lack of woody debris. Many bird species, such as the Hooded Warbler, Red-headed Woodpecker, Eastern Wood-Pewee, Northern Flicker, Nightjars, and many post-fledging juvenile birds utilize canopy gaps for cover, or for foraging habitat, as do some bat species. Lack of fire has also allowed some fire-intolerant mesophytic plant species to become quite common in oak-dominated communities, including the American Beech (Franklin and Kupfer 2004). The resulting loss of acorn production may be limiting for some wildlife in the future.