Forestry Activities
Impacts
Timber harvesting for pulp or lumber occurs on DoD's forested peatlands in the southeast. Activities related to forestry may affect the soils, hydrology, and vegetation of these communities. Modified rubber-tired carriers with wide or dual tires increase mobility, but can cause a large amount of visible damage to the site (Jackson and Stokes 1991). Dual tire skidders are cost effective under wet conditions and are able to work in harsh conditions, but also may leave the site with high levels of disturbance. The capabilities of dual tire skidders might allow loggers to work beyond acceptable ground condition limits (Jackson and Stokes 1991). The resulting soil damage under wet conditions can permanently reduce tree growth on the site (Terry and Campbell 1981). Logging in bay forests that occur on seepage slopes is known to destroy the soil structure of the community (FNAI 1994a). Disrupted soil can become stabilized if vegetation regrowth is successful within a few years following tree harvest (Campbell and Hughes 1991).
The removal of vegetation and alteration of soils with high organic matter content can result in substantial short-term changes in the timing, duration, and discharge rates of flood waters (Ash et al. 1983). Immediately after harvesting there may be temporary increases of fresh water delivery, sediment erosion, and nutrient and chemical loading in runoff waters (Skaggs et al. 1980, Ash et al. 1983). High-flow flushing in rivers due to storm events could transport sediment down channel, where some may enter into small creeks with relatively sensitive spawning beds and nursery areas. The light reduction that results from siltation can have serious effects on aquatic organisms and habitat (Corbett, Lynch and Sopper 1978). Clearing of vegetation near waterways may significantly increase the temperature of surface runoff, adversely affecting aquatic organisms.
Roads running through peatlands may pose a threat to these communities. They function as berms that restrict natural water movement (Miller and Maki 1957, Gosselink et al. 1990) and they expose soil, allowing for increased erosion (Gosselink et al. 1990, Walbridge and Lockaby 1994, FNAI 1994a). Extensive systems of roadsand canals were constructed in the 1980's specifically to increase logging access in Dare County, NC (Laney and Noffsinger 1987).
Nutrients in runoff can increase through fertilization and/or from the release of soil nutrients during soil disturbance. Organic soils contribute large amounts of nutrients to runoff, whether or not they are fertilized, if they are ditched and drained (Hortenstine and Forbes 1972). Erosion of peatlands also results in considerable nutrient export (Crisp 1966). Nitrogen concentration in runoff is much higher in developed areas (pine plantings, etc.), and is highest from mineral soils (Ash et al. 1983). Conversely, phosphorus concentration in runoff is higher in cleared peatlands, and is greatest in deep peat areas (Ash et al. 1983).
Timber harvest directly affects the composition of the peatland plant community. Some species and communities, even though they are adapted to natural distur bance, may not regenerate themselves following logging. Logging and its consequential alteration of hydrology is listed as one of the two processes responsible for the more than 90 percent decrease in white cedar acreage (Frost 1987). AWC often do not regenerate and are replaced by pocosin (Ash et al. 1983, D. Stewart 1996, McKinley and Day 1979) or swamp hardwoods (Frost 1987, Zampella 1987). Shrub-dominated vegetation has been documented as replacing logged AWC stands in the Dismal Swamp (McKinley and Day 1979) and Dare County Air Force Range (Fussel et al. 1995); red maple and black gum have replaced white cedar following logging in the Dismal Swamp (Levy 1987). The rapid growth of hardwood sprouts enables them to gain an initial advantage over the white cedar reproduction that starts from seed. Rapid growth may be the primary reason for the frequent replacement of AWC with hardwoods following cutting (Little 1950). Seedlings may become established under cover of shrubs following logging, but the shrubs rapidly become thick and exclude light, making establish ment of the cedar very difficult (Korstian and Brush 1931, Akerman 1923). Conversion of AWC stands to hardwoods following cutting is increased by leaving many of the larger hardwoods (Little 1950, Frost 1987). Over time, the conversion of white cedar stands may proceed at an increasing rate as more hardwoods reach the overstory and are again left after logging (Little 1950, Frost 1987). This process seems to be influenced in part by the advanced reproduction of hardwoods present before logging and the relative growth rate of the species present (Little 1950).
Slash and brush that remain following cedar harvest also affect the regeneration of AWC. Piles of slash, and surviving shrubs, shade out young AWC seedlings and provide fuel for wild fires, encouraging the establishment of more fire-tolerant pocosin species to the exclusion of AWC (Ash et al. 1983). White cedar seedlings have been observed to form dense stands in cleared areas between masses of slash,while few seeds germinated and still fewer survived under the dense slash (Korstian 1924). Areas that are relatively free of logging debris have been observed to have 30 to 40 times as many seedlings as areas with debris. In slash-free areas, the largest seedlings were two to four times taller than those found in slash-covered areas (Little 1950). Hardwood sprouts are able to emerge through dense slash, however, and by the time slash has decayed sufficiently to form a seedbed suitable for white cedar, the hardwoods have become so tall that they form the main part of the stand. Logging slash, therefore, results in regeneration of mixed stands (Korstian and Brush 1931).
AWC do not become established in the hollows of the naturally hummocky microtopography of the forest floor (Figure 11), only on the elevated mounds formed from roots and debris (Akerman 1923, Ehrenfeld 1995). Akerman (1923) observed that only the moss-covered logs, stumps, or hummocks that are above the water level form favorable seedbeds during periods of high water in the spring and early summer. Logging operations may reduce the elevation of these mounds. Logs laid down to create skid trails (Figure 12) sink over time (Figure 13) and cause depressions in the soil that last for several years. These depressions fill with water making them unsuitable for reestablishment by cedar (D. Stewart, 26 March 1996). Logging may also reduce the natural cover of sphagnum moss characteristic of this habitat; Ehrenfeld and Schneider (1991) stated that sphagnum moss is sensitive to trampling (Studlar 1983), changes in the hydrological regime (Andrus, Wagner, and Titus 1983), and elevated nitrogen concentrations caused by fertilization (Press, Woodin, and Lee 1986). The decline in cedar establishment following logging may be related to the decline of sphagnum moss following disturbance (Ehrenfeld and Schneider 1991). Sphagnum moss is the substrate on which cedar reproduction is generally found (Little 1950) and it holds a large reservoir of buried viable seed (Korstian 1924, Little 1950). Changes in Sphagnum spp. cover may have important implications regarding successional change and community dynamics (Ehrenfeld and Schneider 1991).
Figure 11. Hummocky microtopography of the Atlantic White Cedar forest floor.
Figure 12. Skid trail built with downed logs on wet peat soils in North Carolina.
Figure 13. Older skid trail with sinking logs, North Carolina.
Despite the many cases in which AWC has not regenerated following logging, it has been suggested that clearcutting helps maintain this community type by mimicking the stand-killing fires of the past (S. Smith, 20 March 1996; Little 1950). Apparently, the success of regeneration depends on site-specific conditions and timing of disturbance following timber harvest (Figure 14; Little 1950). Whether or not fire is beneficial for white cedar regeneration following clearcutting depends on several variables. These include: hardwood composition and abundance in the original stand, numbers of viable seed stored in the forest floor at varying depths, the composition of nearby stands that survive the fire and will disperse seed over the burn, the depth to which the fire burns into the forest floor, and the position of the water table after the burn (Little 1950). Further study is needed to better understand the factors involved in successful AWC regeneration.
Repeated cutting of AWC forests has created younger stands that are more susceptible to damage; in addition, repeated removal of the competing overstory has encouraged shrubby understories. Such understories would be absent under a natural closed AWC canopy, particularly if affected by periodic, light fires; when understories do exist, they tend to increase the intensity of any fire (Little 1950).
Cypress dome communities are also affected by timber harvests. Changes in harvesting equipment and marketing have made the clearcutting method of regeneration a much more common management practice. Now small and large trees are just as likely to be cut. Additionally, modern equipment allows deeper penetration into wetlands (Ewel, Davis, and Smith 1989). Although cypress trees can reproduce vegetatively from stumps and produce cones within 2 years, logging in cypress wetlands has been reported to result in poor cypress regeneration and changes in species composition (Bull 1949, Allen 1962, Gunderson 1977). Drainage of cypress domes to improve access for timber harvest often favors hardwood regeneration at the expense of cypress (Marois and Ewel 1983). In some cases, though, cypress reproduction has responded favorably to clearcutting, presumably due to the increased light conditions (Marois and Ewel 1983). Ewel, Davis, and Smith (1989) concluded that clearcutting without immediate burning, and with no alteration of the hydrology, has little long-term effect on ecological and hydrological patterns on the community and surrounding areas. Because of the importance of cypress domes to wildlife and endangered species, however, the practice of clearcutting has undergone scrutiny (Ewel, Davis, and Smith 1989) and is not presently practiced on military installations (Laurie Gaywin, The Nature Conservancy, Savanna, GA, professional discussion, 15 May 1996).
Pond pine woodlands is another community sometimes used for logging. Pond pine woodlands in North Carolina that were cut and not reseeded, and were protected from fire, contain almost no pond pine. This suggests that logging is not an adequate substitute for fire to promote the regeneration of this species (Fussel et al. 1995). Pond pine is harvested mostly as pulpwood, since it lacks the straight boles of other pines, like loblolly and slash pine (S. Smith, 20 March 1996). Harvesting for pulpwood is disadvantageous compared to harvesting boles of trees and leaving leaves and branches since it results in a considerably larger export of nutrients from the ecosystem (E. DeLucia, Professor, Department of Plant Biology, University of Illinois, professional discussion, 17 March 1996). Often, pulpwood harvest of pond pine is conducted after draining the area and is followed by reseeding with slash or loblolly pine (Ash et al. 1983).
Management Recommendations
Management of peatland forested communities in sites and watersheds where TES conservation is a primary concern should seek to minimize soil disturbances and erosion-related impacts to waterways, and should promote the native species, structural characteristics, and disturbance processes that enhance TES survival and reproduction. Although the relationship between peatland habitat require ments of TES species and human activities largely has not been documented, recommendations here are based on review of known conservation literature.
Intensive management for maximum wood production should not be practiced near ditches, streams, or other bodies of water. Buffer strips between areas of erosion and watercourses should be maintained permanently, and their effectiveness should be monitored. Within buffer strips, only selective harvesting should be practiced, and use of heavy equipment, prescribed burning, and application of fertilizers and pesticides should be avoided. To protect waterways from aerial, ground vehicle, hand spraying, and hand injection methods of pesticide application, untreated buffer strips of 30, 15, 7.5, and 4.5 meters, respectively, are recommended (Ash et al. 1983). Pesticide use in forests is best limited to precise applications in specific areas, avoiding widespread aerial application (Ash et al. 1983). When it is judged necessary to use pesticide and/or fertilizer on peatlands, it is best to avoid application during times of high rainfall and runoff, to prevent pollution of surrounding community types (Ash et al. 1983).
Clearcut sizes should be minimized, ideally including no more than 5 acres, with buffer strips between cuts. Implementing smaller individual clearcuts helps to prevent erosion and runoff immediately following clearcutting (Ash et al. 1983) and reduces impacts to wildlife (D. Stewart, 26 March 1996).
Roads that are not used for logging, military, or recreational needs should be closed and managed for erosion problems (FNAI 1994a). After harvest, roads should be closed, seeded with vegetation, and barricaded if possible. In forested peatlands, forest buffer strips of 30 m should be maintained between roads and streams or ditches. In shrub-dominated pocosins, where the road must be built next to a canal, an interception ditch filled with vegetation should be created between the road and canal (Ash et al. 1983).
Several alternatives exist for low-impact harvesting systems on wet soils. The following suggestions are taken from Jackson and Stokes (1991).
Felling: Mechanized felling can be accomplished using swing feller-bunchers on tracks. Although costly, this equipment reduces disturbance by limiting the amount of travel on the site and by using wide tracks. Under certain circumstances, mats may be desired to increase feller-buncher mobility and reduce site disturbance. Felling technology is now available that includes lightweight, long-reaching machines that combine high production with little disturbance. Use of grapple-saws would increase the flexibility of the feller-buncher since the weight on the end of the boom would be reduced and bucking and topping problems should be minimized. Such a machine can cut the trees, remove the tops and some of the larger limbs, buck logs, and pile stems. Integrating all of these functions into one machine can reduce subsequent extraction impacts.
Extraction: Vehicles with wide tires or tracks are recommended since they reduce rutting of the soil and the resulting hydrologic impacts. Fifty and 68-inch-wide tires have been used in the southern United States. Such tires may exert pressure as low as 3 psi, and are still relatively maneuverable. Mellgren and Heidersdorf (1984) list the advantages of extra-wide tires, including: increased productivity, fuel savings, reduction in ground disturbance, less soil compaction, smaller machine require ments, smoother ride, improved stability, and increased access to timber. Disadvantages were listed as high price, reduced maneuverability, and necessity for specialized repair and maintenance equipment.
Flexible tracked skidders have been reintroduced; design changes decreased operating costs to the point that such machines may be cost effective. Advantages of track skidding over tire skidding include lower ground pressure and higher traction. These have been observed to have lower overall soil impacts in peat soils (D. Stewart, 26 March 1996).
Large, six-wheel drive, wide-tire forwarders in combination with grapple skidder, feller-bunchers, and in-woods loaders can significantly reduce the number of logging roads needed; they may also make logging feasible where conventional systems cannot operate. Such equipment allows access to roadless areas in such a way that also improves stability, safety, and comfort, requires less maintenance, and provides greater productivity, because the machine stays on top of even saturated ground, which also reduces residual damage to the site (Griffin 1989). Large payloads reduce the number of passes required on the same trail. The clambunk skidder has been used successfully in the marsh lands of Canada. It has a loaded psi of 4.8 with 68-inch tires and 7.4 with 44-inch-wide tires. Generally the productivity of one large capacity forwarder or clambunk skidder is equivalent to three regular skidders. It is easy to imagine how such equipment may reduce the damaging effects that logging can have on peatland forests (Jackson and Stokes 1991). Quantitative research is needed at this time to determine whether the benefits this equipment offers is adequate to allow intensive forestry operations to coexist with TES habitat on peatland soils in the long run.
Transport: Since building roads is more disturbing to the site than harvesting, and since roads are expensive to build and maintain, options that allow log removal on lower quality roads or transport of wood further without roads are advantageous. Central tire inflation (CTI) systems that allow the use of low-pressure tires onlogging trucks can permit the trucks to operate on low quality roads and reduce road maintenance. Special matting and matting-handling equipment may allow the use of low-quality roads and reduce residual disturbance (Jackson and Stokes 1991).
In addition to these general management recommendations, the different peatland communities discussed in this report may have specific requirements. Bay forests that serve as TES habitat and occur on seepage slopes should not be harvested, since the machinery involved would be likely to permanently alter the soil structure and hydrology required to maintain this community (Wharton 1978).
Basin pocosins are affected indirectly by logging or road construction in adjacent areas. Forestry practices throughout watersheds that supply water and nutrients to pocosin wetlands should minimize changes in hydrologic input, nutrient and chemical input, and siltation from uplands, if management objectives include conservation of TES that rely on the basin pocosin community for habitat (Ash et al. 1983).
Although harvest of cypress domes is not reported to occur currently on DoD lands, nearby logging of adjacent areas may lead to impacts. When nearby logging occurs, adequate buffer zones should be maintained between the cypress dome and logging activities. Buffer zone recommendations range from 30 to 50 meters for other plant communities with similar drainage characteristics (i.e., herbaceous seeps in the Southeast; Platt et al. 1990; Palis and Jensen 1995). Because there is little quantitative data to guide buffer zone design in peatland communities, managers should closely monitor areas potentially affected to determine if a larger buffer zone might be needed (Harper et al. 1997). Maintaining adequate buffer zones will avoid direct disturbance of rare plants in the ecotone, decrease siltation, and prevent the addition of chemicals into cypress domes during precipitation events.
AWC forests are a rare community that has adapted to an identifiable disturbance regime that has largely changed; remnant examples of these forests should receive high priority for conservation and old growth characteristics. Across an entire landscape, many separate high quality sites should be maintained to increase species diversity and improve survival probability in the face of catastrophic fire, disease, or storm damage.
Conservation of different successional stages is also desirable across the landscape, so if one patch of AWC is destroyed, sufficient similar patches persist. Although the oldest stands are most attractive for harvesting, some climax communities should be protected since these rare mature stands require many years (200 to 300) fortheir development (Ash et al. 1983). Old growth forests are particularly valuable for both species richness and abundance of wildlife (Carter 1987).
If logging of an AWC is determined to be desirable, and the site does not serve as TES habitat, the following practices may increase the probability that a high quality stand of AWC may regenerate:
1. Cut all trees in an area, including all hardwoods. Cutting all hardwoods in areas logged for AWC will promote pure AWC stands, since advanced recruitment of hardwoods results in mixed stands at best. Furthermore, removal of competitive species may be required during early years of the stand development (Little 1950).
2. Cut 5 acres or fewer at one time, leaving a thick band or dense patches of mature AWC on the western edge of the harvest site, to serve as seed sources. Distance and direction from a seed source greatly affect the establishment of white cedar seedlings. Because of the prevailing westerly winds in most areas where this habitat occurs, white cedar reproduction extends rather slowly westward where seed dispersal from tall trees is as little as 20 m. The establishment of white cedar is favored on the eastern side of seed sources. It is advisable to leave at least some large trees on the western edge of a small clearcut to provide seed in case the seed source in the soil is not sufficient for regeneration, or the first cohort of regenerat ing cedar fail to survive (Little 1950). Cutting in strips, checkerboard patterns, or small areas within larger AWC forest has been reported to facilitate satisfactory reseeding from the remaining individuals (Cottrell 1929, Noyes 1939, Little 1950), and is consistent with management goals to preserve older stands for wildlife. Strips with widths of 30 to 50 m have been recommended (Moore 1946), depending on the heights of the surrounding trees (Little 1950). Older trees produce more seed of higher genetic value (Little 1950). Leaving small stands is more advisable than leaving isolated trees because of the risk of windthrow (Little 1950, Moore and Carter 1987).
3. Create and use minimal roads into the stand, and the fewest number of passes possible.
4. Clear all brush and slash piles. Following the harvest and during a period with a high water table, conduct a light prescribed burn on the site to totally eliminate slash.
5. Control hardwood competition during early stand formation. This is important since the tree species that are present in the early stages of succession tend to remain or increase in the stand over harvest cycles (S. Smith, 20 March 1996).
Fire Management
Impacts
Fire is the dominant natural disturbance in the southeastern United States; many plant communities in the region are adapted to this disturbance and even depend on fire for persistence. However, one community discussed here (bay forests) is destroyed by fire, and the other communities are adapted to certain intensities and frequencies of fire. A fire regime characterized by more frequent, less frequent, or more intense fires will serve as a negative impact to most of these communities. Some of the decline in these communities is due to almost complete fire suppression, which may result in loss of habitat for endangered species (Sutter and Kral 1994).
The bay forest community is considered a late-successional community that is destroyed by fire. Bay forests usually revert to a grass-sedge community, basin or streamhead pocosin, or AWC forest after burning occurs (Penfound 1952). In areas where bay forests serve as valued wildlife or TES habitat, fire should be considered detrimental.
Unlike bay forest communities, AWC communities depend on periodic fire to create conditions for successful regeneration (Motzkin, Patterson, and Drake 1993). It is thought that fire return intervals of 25 to 250 are appropriate for maintenance of AWC forests (Frost 1987).
It has been known since at least 1924 (Korstian 1924) that AWC regenerates following a fire during a period of high water table. Under moist conditions, fire does not burn the top layer of peat in which there may be stored enormous numbers of viable seeds. With fire control and fragmentation of large peatlands, suitable fires have become extremely rare. The loss of natural regeneration, coupled with widespread logging and draining, have restricted these once-abundant communities to rare sites throughout their range (Fussel et al. 1995).
Despite the requirement for occasional catastrophic fire for community persistence, frequent fire is harmful to the AWC communities under certain conditions. Intense fire kills the adult trees, with regeneration coming from a seed bank in the peat. However, many hardwood competitors can sprout from roots if the fire is of moderate intensity. For this reason, certain fire regimes are detrimental to high quality AWC forests. Younger stands are more susceptible to fire damage than older ones (Little 1950). Little (1950) stated that the effect of fires on the white cedar community had not been as positive as concluded by Buell and Cain (1943), and that fire and cutting have usually worked together to reduce the proportion ofwhite cedar compared to other associated species. Severe fires, when the soil is dry, destroy the upper layer of peat and the cedar seed bank (Buell and Cain 1943).
Fire was probably less harmful in pre-settlement times. There was a far greater supply of seeds since relatively old and large stands stored more seeds in the peat within the stands, as well as in adjoining areas. Frequent fires in the surrounding habitats were not intense and were less likely to penetrate the stands (Little 1950). Fires that could penetrate into these wet areas would have been hot enough to prevent sprouting by associated hardwoods. Following such a burn, the large amount of wind-distributed seed from old growth stands nearby had a good chance of restocking the areas when moisture conditions became suitable (Little 1950).
Intense fire on peat soils may not only destroy seed reserves but also lower the soil surface, causing the community to revert to a more hydric community such as cypress swamp or pocosin if the water level stays relatively stable (Little 1950, Levy 1987). Such conditions favor the development of a hardwood swamp (Buell and Cain 1943).
Fire suppression has been responsible for the vast reduction in the switch cane understory once characteristic of pond pine woodlands (Hughes 1966). Estimates of the original extent of cane dominated areas are 250,000 acres in Virginia (Frost 1989) and 2 million acres in Virginia and the Carolinas (Hughes 1966), whereas the estimate was as low as 2000 acres in 1989 (Frost 1989). It is likely that large areas that are now dominated by pond pine with dense broadleaf evergreen vegetation were once dominated by pond pine/cane (Type I community) when the natural fire regime was prevalent. An extensive area dominated by this community in North Carolina has declined greatly just since being described in 1982 (Fussel et al. 1995).
Fire suppression is a primary threat to remaining streamhead pocosin communities. Fire suppression is believed to eventually kill rough-leaved loosestrife due to shading by shrub dominance, but the endangered plant may persist for years or decades under a fairly dense shrub layer. Plow lines constructed to control fire in upland communities can adversely affect streamhead pocosin hydrology by channeling sheet flow surface water away from the site and by promoting severe erosion (Frantz 1995, Harper et al. 1997).
Fire, which has historically occurred in cypress domes during the dry seasons, is an important factor in preventing the dominance of cypress wetlands by other tree species (Cypert 1961, Gunderson 1977, Ewel and Mitsch 1978, Marois and Ewel 1983). Periodic fires will not significantly affect the species composition of normally wet domes, but does maintain cypress domination in drier domes by killing newlyestablished slash pines and hardwoods (Ewel and Mitsch 1978, McCulley 1950). Fire may kill younger cypress but they generally resprout from the stumps (Kurz and Wagner 1953). Light burning has been observed to increase cypress regenera tion while severely burned cypress swamps tend to favor regeneration of black gum (Ewel, Davis, and Smith 1989).
Firebreaks surrounding cypress domes are detrimental to the biota in this community type. Besides physically disturbing the soil and hydrology of the depression, they exclude fire that is necessary for the maintenance of habitat required for native plants and animals. Fire suppresses the development of a thick shrub layer, opens the canopy, and allows the light penetration that is necessary for herbaceous growth. Rare plants including Curtiss' sandgrass, Boykin's lobelia, and Chapman's butterwort require the open, meadow-like environment of cypress dome perimeters maintained by fire under natural conditions. Chapman's butterwort may appear upon creation of pine plantations, but disappears when three layers of vegetation close over it, probably due to shading and reduction of soil moisture (Kral 1983). In cypress ponds, the herbaceous layer that is sensitive to fire regime is also important in providing habitat to endangered amphibians (TNC 1995).
Overgrowth of shrubs and loss of the herbaceous layer due to a combination of changes in the natural hydrology and fire suppression are common factors in the degradation of basin peatland communities on DoD lands (TNC 1995, FNAI 1994a). Fire suppression in low, high, and small depression pocosins results in the reduction and disappearance of the herbaceous layer and the characteristic herbaceous openings that support most of the TES plants found in the community (Fussel et al. 1995; T. Cruise, 8 April 1996). Relatively frequent fire also is important for the release of nutrients, especially phosphorous, that are limiting in this habitat (Wilbur and Christensen 1983).
Management Recommendations
Any fire regime will favor some plant communities over others, and some species over others. Managers must first and foremost identify the landscape that they desire and apply fire appropriately through time and space to maintain the desired mix of species and community types. General information for fire management in support of different peatland communities follows.
Bay Forests. Protection from fire is required to maintain bay forests since they are late successional communities. If managers believe that a bay forest has taken theplace of another, more desirable, community type, due to unnatural changes in the fire regime, then prescribed burning would be appropriate.
AWC Forests. It is clear that under natural conditions, the AWC forest is dependent upon periodic, sometimes infrequent, burns. However, under human influence, the community has largely been logged and converted to young stands, often mixed with hardwood species. Throughout most, if not all, of the AWC range, it is currently more important to retain stands and encourage old growth characteristics, than to convert additional sites to earlier stages (NCNHP and TNC 1995). Although details about the requirements of TES in AWC habitat are not readily available, there is no information suggesting that prescribed burning is necessary or desirable for TES conservation in this community. It would be unusual to identify a mature AWC stand for which protection from disturbance, at least for many decades, is not recommended on the basis of TES conservation and natural values considerations.
Pond Pine Woodlands. It is recommended that pond pine natural communities be burned at 5- to 8-year intervals. The entire area should not be burned at one time but should be divided into several burn units to prevent extirpation of insect populations (Fussel et al. 1995) and to comply with smoke regulations (T. Cruise, 18 April 1996). Growing season burns are preferable since they mimic natural fire regimes (Fussel et al. 1995). Areas with remaining stands of switch cane should be given high priority for burning and implementation of a frequent fire regime to preserve and encourage the spread of this habitat type through clonal regeneration (Hughes 1966). Five- to 8-year burn intervals should allow for habitat diversity on the landscape, since the recently-burned sites will have an almost-pure understory of switch cane, while sites that were burned earlier will have an increased shrub component to the understory (Frost 1989). Extensive areas are known where cane persists in varying densities under pond pine forest and under closed canopies of pond pine and hardwoods growing on peatland soils (Frost 1989). If cane doesn't appear (from a persistent rhizome mat) following fire, it may have to be re-introduced through cuttings or seed, since it does not have a persistent seed bank (Hughes 1966).
Basin Pocosins. Prescribed burning is recommended for low pocosins. Though the optimal fire frequency is not known, an average rotation of 20 years is suggested as an initial approximation. In North Carolina, a reduction in abundance of cranberry or northern white beaksedge is used to indicate the need for a prescribed burn (Fussel et al. 1995). In general, the need for fire can be assessed by the extent of the herbaceous openings within the low pocosin (Fussel et al. 1995; T. Cruise, 18 April 1996).
Prescribed burning for high pocosins is recommended at 5- to 8-year intervals. The entire area should not be burned at one time but should be divided into at least three burn units to prevent extirpation of insect populations (Fussel et al. 1995) and to stay within regulations for smoke production when necessary (T. Cruise, 18 April 1996). Growing season burns are preferable in that they mimic the natural fire regime (Fussel et al. 1995). Intense fires may occur in areas where flammable organic matter has built up due to fire suppression earlier in the century; in these cases, the peat may burn. Managers are attempting to control the hydrology of burn units in order to control burn intensities. The water level is managed through pumping stations and flashboard risers to allow the vegetation to burn without ignition of the peat. The water level may be raised to extinguish the fire (T. Cruise, 18 April 1996).
Streamhead Pocosins. Management of fire in streamhead pocosin habitats should consider the rare plant species present. Fire return intervals of 3 to 5 years are recommended for bog spicebush and/or rough-leaved loosestrife. Since these species require shading, additional experiments should examine whether a fire return interval greater than 5 years may be beneficial to these species. Three- to 5-year fire return intervals are recommended for Carolina asphodel as well (LeBlond, Fussell, and Braswell 1994a). Pondspice is fire tolerant but seems to respond negatively to annual or biennial fire regimes (TNC 1995), so an initial fire return interval of 3 to 5 years should be implemented and monitored. Where Carolina goldenrod occurs alone, shorter than 3-year fire intervals should be conducted experimentally. Carolina goldenrod occurs with pondspice on some installations, and in these cases, a 3- to 5-year burn cycle should be used to maintain both species (Schafale and Weakley 1990, TNC 1995). To help determine the appropriate fire frequencies for different sites and different species, a monitoring program is recommended. The program should assess natural burn frequencies when fires are allowed to invade pocosin ecotones, and the resulting effects on TES plant survival and reproduction. It is possible that the moist, shrubby end of the moisture gradient, where pondspice typically occurs, is naturally limited in its frequency despite frequent fires in the surrounding upland and further upslope, where Carolina goldenrod occurs.
All of the above species require continuously moist substrates for survival, and so maintenance of the natural hydrology of these sites is imperative. Digging ditches and creating fire plowlines that alter site hydrology should not occur in these areas. Existing fire plowlines should be filled in with native soil, if possible, without use of machinery that would cause further damage to the site.
Cypress Domes. Fire has occurred historically in cypress domes during dry periods, and is a useful management tool for maintaining desired plant composition of cypress domes. Burns of the upland-cypress dome ecotone are recommended at 2- to 5-year intervals, coupled with a monitoring program to determine the effect on rare plants and animals. When combined with restoration of natural hydrology and the removal of firebreaks, the fire regime of cypress domes should not differ from that of the surrounding pine woodlands under natural conditions. Monitoring should be designed to assess the natural burn frequencies when fires are allowed to invade cypress-upland ecotones, and the resulting effects on TES plants (FNAI 1994a). Adjustments in burn interval and intensities should be made as needed. Prescribed burning should be used to maintain a meadow-like habitat on the edges of cypress domes where Boykin's lobelia, Chapman's butterwort (Kral 1983), savanna aster (Godfrey and Wooten 1981, FNAI 1994a), and Curtiss' sandgrass (Johnson 1993) are found. Pondspice, although it is fire tolerant and can sprout from roots after burning, may be harmed by a frequency of fire that other rare plants of the habitat can endure, such as annual or biennial burns. Of course, burns conducted when pondspice are surrounded by standing water will protect the species, even if the edges of the dome successfully burn (TNC 1995).
Rehabilitation of fire-excluded cypress domes may require burning to reduce fuel loads. Burning should be done in the dormant season to minimize smoke and safety problems that would occur during the growing season (FNAI 1994a). However, winter burns should not be carried out if there is concern about harming amphibian populations, such as the endangered flatwood salamander, which deposits its eggs on grasses during the winter (TNC 1995). Ideally, burning should be conducted in the spring, specifically from March to June. This is when natural ignitions from lightning strikes have been most likely to occur under historic conditions. In Georgia and the Carolinas, spring burns are less likely to harm amphibian populations. On the Gulf coast where these habitats are wettest in the winter, spring burns would be more effective than winter burns (FNAI 1994a). Spring burns should be conducted at such a time when the surrounding habitat and dome margins would be dry enough to burn adequately, at which time salamanders are least likely to be migrating through the grassy ecotones.
In the case of a conflict between fire management recommendations for cypress domes and the surrounding upland (for example, if the cypress dome was located near a stand managed for timber or an urban area), fire may be restricted to the cypress dome site using a temporary fire line. The isolated wetland, the wetland-upland ecotone, and a buffer zone of upland forest should be included within the fire break, which is placed in the upland community. Implementing isolated burns may circumvent restrictions regarding smoke production that would otherwisediscourage early growing season burns (FNAI 1994a). After the burn is conducted, the fire plowline should be revegetated with native species and managed to prevent erosion.
Hydrologic Management
Impacts
Massive disruption of wetlands hydrology has occurred over 300 years of drainage efforts throughout the southeast (Frost 1987). Some natural communities have been affected over very large areas by conversion to urban and agricultural lands, while other communities are more at risk from localized activities within a small watershed. Bay forests and other communities that occur on seepage slopes are an example of the latter. These small areas can be severely affected by use of off road vehicles (FNAI 1994a) and road construction. Off-road vehicles (ORVs) damage vegetation directly and alter the natural hydrology by rutting and compacting the soil. Once soil stability is compromised, the sandy soils form erosion gullies that channel water off the hillside. Channelization and the subsequent drainage is devastating to this community (Wharton 1978), since most wetland plants are very sensitive to slight changes in soil moisture regimes (reviewed in Harper, Trame, and Hohmann 1998). Streamhead pocosins experience similar degradation due to channelization and drainage, since the hydrology is similar to seepage slope bay forests.
Lowering the water table across landscapes that support AWC forests will result in the replacement of white cedar by species tolerant of the drier conditions (LeBarron and Neetzel 1942; Penfound 1952). Ditching near logged AWC stands has promoted rapid drying and dominance by species usually occupying drier sites (Levy 1987). In the Dismal Swamp, an extensive network of ditches and roads have lowered the water table, adversely affected the establishment and growth of white cedar seedlings, and increased the risk of fire (Akerman 1923). This drainage network also has allowed soil moisture conditions that favor establishment of hardwood species (Hickman and Neuhauser 1977). Lowering the water table may result in subsidence of peat, oxidation, and the exposure of mineral soil (Frost 1987).
Low, high, and small depression pocosins are affected by ditching and drainage of the soil. Ditching at and below the interface of the peat and mineral layer increases discharge into estuaries because base flow contribution from the mineral layer occurs (Daniel 1981). By the 1960's, most pocosins were severely dissected bydrainage canals dug for the purpose of draining adjacent areas for pine silviculture (Ash et al. 1983.)
Alteration of the natural hydrologic cycle of cypress domes may reduce cypress regeneration since cypress depend on fluctuating water levels for germination (Demaree 1932, DuBarry 1963). Growth rates of cypress are highest in areas that are neither very wet nor very dry, due to the respective limitations of oxygen and water for growth (Marois and Ewel 1983). Water levels that are maintained at unnaturally high levels and not allowed to draw down during the dry season prevent establishment of cypress. Many amphibians require total draw-down at some point for reproduction, since drying out eliminates predators (TNC 1995). Limited drainage increases cypress growth rates, but the drier conditions of cypress domes that have unnaturally lowered hydrology and shorter hydroperiods are associated with changes in the plant community; hardwood species increase in importance and absolute density, shrubs increase in density, and slash pines may invade the cypress dome (Marois and Ewel 1983). These plants are not as tolerant to flooding as cypress and are restricted under natural hydrological conditions (Conner and Day 1976). Since most hardwoods may become established under lower light levels than cypress (Fowells 1965), high shrub densities in the drier cypress domes further reduce cypress regeneration by favoring competitive hardwood seedlings and saplings (Marois and Ewel 1983).
Maintenance of the natural hydrology of cypress domes is important to the rare plants found in this habitat on military installations. Boykin's lobelia, pondspice, and Chapman's butterwort require shallow standing water or wet peaty soils to persist (Godfrey and Wooten 1981, Kral 1983). Following ditching for drainage, Chapman's butterwort often lines ditches, where moisture conditions are still adequate, but the plant disappears once drainage is complete enough to dry out the site (Kral 1983). Curtiss' sandgrass inhabits shallow, temporarily flooded parts of cypress depressions and grows in a band surrounding deeper areas, suggesting it requires a specific hydrology to persist (Johnson 1993).
Since drainage through ditch construction is standard timber management practice for pinelands in poorly drained areas (Schlaudt 1955), cypress domes within these areas are often drained as well. Following drainage the ditches may be used for planting slash pine or used to facilitate drainage of surrounding pine sites. On the other hand, ditches and plowlines that circle the cypress dome, often dug for fire protection, can increase the natural water level by holding water (TNC 1995) and preventing water from seeping out through transpiration of trees in the surrounding uplands (Crownover et al. 1995). Berms of soil placed around cypress domes may also decrease water levels by restricting water flow into the cypress dome (Brown1981). Ditches dug across cypress domes and connected to lower areas may drain the cypress dome and decrease its natural water level. Connections with other wetlands may lead to introduction of foreign fauna, including fish that are predators of native salamanders. Pine plantations around cypress domes may also lower the water table of cypress domes because they increase transpiration in the surrounding area (Marois and Ewel 1983).
Management Recommendations
Seepage slopes should be closed to all vehicular traffic (FNAI 1994a). Ditches and firebreaks should not be dug, and existing ditches and fire breaks should be filled and re-contoured using local soil.
The natural hydrologic regime of the basin pocosin habitats is desirable to prevent the community from succeeding to a different vegetational type, such as low pocosin to high pocosin or high pocosin to pond pine woodland (Ash et al. 1983).
In areas where TES conservation is a priority, fire rings and trenches around, through, and between cypress domes should be closed and revegetated to maintain the moisture regime required by TES plant species and the flatwoods salamander. Maintaining a natural hydrological regime is also necessary to implement a fire regime that supports the biota of this ecosystem. Maintenance of a natural forest structure in upland communities surrounding cypress domes will provide natural transpiration rates and therefore natural rates of water movement into and out of the cypress domes (FNAI 1994a).
Chemical Pollution
Impacts
The pocosins of the Atlantic Coastal Plain are important nutrient filters for the maintenance of water quality in rivers and estuaries, as long as water flows through them at the slow rate characteristic of the undisturbed community. The dissection of these habitats by canals dug for drainage to promote agriculture and agro-forestry has reduced the ability of these wetlands to filter pollutants. Since much of the productive marsh area of the Atlantic Coastal Plain is in close proximity to pocosins, there is appropriate concern about potential pollution from pocosin development (Ash et al. 1983). Juvenile stages of aquatic organisms are dependent on stable patterns of substrate and salinity provided by the filtering action of pocosin wetlands. Nutrient enrichment increases growth of pathogenic bacteria(Ash et al. 1983). Nutrient enrichment of this habitat allows numerous competitive species to be supported, while native species are eliminated (Ehrenfeld and Schneider 1991).
Although net water flow is in most cases outward from cypress domes into the surrounding pineland community, water flow is slow enough that any solutes, such as fertilizers and pesticides, may affect the soil and habitat if brought in from the pinelands during precipitation events (Pionke and Chesters 1973).
Management Recommendations
Water flows into cypress domes during precipitation events, and outward during drier conditions when the water table is low. Thus, fertilizers and pesticides, if used at all, should be applied to surrounding uplands during dry periods (Crownover et al. 1995).