Managing Shortleaf Pine with Prescribed Fire

Management Considerations for Wildlife

From early seral stages through late seral stages of stand development, shortleaf pine provides habitat for a large number of wildlife species.  Well-spaced seedlings of less than about 1,730 stems/ha (700 stems/ac) and in young sapling stands up to about 2 m (6.5 ft) prior to canopy closure provide some value as cover for early seral species such as many small mammals, eastern cotton-tailed rabbit (Sylvilagus floridanus) and northern bobwhite (Colinus virginianus).  Saplings provide beneficial escape and bedding cover for white-tailed deer (Odocoileus virginianus) in naturally or artificially regenerated stands (Masters 1991a,b; Masters et al. 1997).  Use of these stands is extended when prescribed fire is introduced early and at least on a 3-year late-dormant season cycle.  Elk (Cervus elaphus) populations also use dense sapling stands in areas where elk restoration efforts are underway (Masters et al. 1997).  Deer and elk also use saplings as territorial marking sites or antler rubbing sites during the rut.   When high stem densities develop, use by either species will decline rapidly with canopy closure where fire is excluded (Masters 1991a, b; Masters et al. 1997).  

Early successional songbird species such northern bobwhite and Bachman’s sparrow (Aimophila aestivalis) make some use of sparse regenerating stands as long as adequate ground cover and some scattered hardwood brush are present.  Where ground cover is predominantly needle litter in dense sapling stands, species such as the prairie warbler (Dendroica discolor) and hooded warbler (Wilsonia citrina) have been noted.  Periodic burning on at least a 3-year rotation in young sapling stands ensures that numerous small mammals, bobwhite, turkey and numerous songbirds will continue to use the stands as they develop (R. E. Masters, Tall Timbers Research Station, unpublished data).  

Once a shortleaf stand enters the post size-class (the smallest merchantable size class), use by wildlife will decline dramatically in dense stands if fire is excluded.  At age 12-15 depending on the site index, many songbird species characteristic of later stages of succession will once again begin using the canopies of shortleaf stands as well as stands of other southern pine species (R. E. Masters, Tall Timbers Research Station, unpublished data).  The importance of fire in retaining early seral wildlife species was recently shown in a study that examined northern bobwhite use of these types of stands.  Following only 3-4 seasons of fire exclusion, northern bobwhite began avoiding stands with densities ranging from 1,483-1,730 stems/ha (600–700 stems/acre) that were once heavily used (Walsh 2004).

A host of song birds use the canopies of pole-sized [average diameter of 15-25 cm (6-10 inches)] stands and to a much lesser extent the understory where frequent fire is used.  The songbird species complement in pole stands is similar to mature stands (Wilson et al 1995, Masters et al. 2002).  In mature stands excluded from fire, both species richness and density of small mammals and songbirds decline markedly as midstory hardwoods develop, and as the herbaceous layer declines from litter buildup and shading by hardwoods (Masters et al. 2002).  However mature shortleaf pine-bluestem stands, which are characterized by abundant herbaceous ground cover, basal areas less than 16 m²/ha (70 ft²/ac), little to no hardwood midstory, and managed with late-dormant season fire at three year intervals, show dramatic increases in both richness and density of small mammals and songbirds (Wilson et al. 1995; Masters et al.1998, 2002).  These low basal area pine-bluestem stands managed with frequent fire also provide more than adequate forage for white-tailed deer (Masters et al. 1993, 1996) of high nutritional quality (Masters 1991a) and are used to a greater extent than unburned closed-canopy sites (Masters et al. 1997).  At least 11 species of breeding birds are considered pine-grassland obligates and are benefited by pine-bluestem management (Wilson et al. 1995, Conner et al. 2002, Cram et al. 2002, Masters et al. 2002).  These include red-cockaded woodpecker (Picoides borealis), red-headed woodpecker (Melanerpes erythrocephalus),  brown-headed nuthatch (Sitta pusilla), northern bobwhite, prairie warbler, pine warbler (Dendroica pinus), eastern bluebird (Sialia sialis), Bachman’s sparrow, chipping sparrow (Spizella passerina), eastern wood-pewee (Contopus virens), and indigo bunting (Passerina cyanea) (Wilson et al. 1995, Cram et al. 2002, Masters et al. 2002).  These species are distinctly disadvantaged by fire exclusion and following mid- to upper midstory development will cease use of these stands (Wilson et al 1995).  This suite of species has declined more precipitously than any other group of songbirds in eastern North America (Jackson 1988­).  Midstory hardwood development has been directly associated with cavity tree abandonment by red-cockaded woodpeckers and subsequent populations declines (Masters et al. 1989, Jackson et al. 1986).

As a food resource, shortleaf pine seed provides an important and preferred food source for northern bobwhite (R. E. Masters, Tall Timbers Research Station, unpublished data) and for numerous small mammals (Stephenson et al. 1963) including gray squirrel and numerous ground feeding song birds (Martin et al. 1951).  Extensive consumption of shortleaf seed by many songbirds and small mammals has been reported as a hindrance to suitable seedling establishment from either natural seedfall or direct seeding of sites (Lawson 1990).

Snags are important for primary and secondary cavity nesting songbirds (e.g., red-headed woodpecker and eastern bluebird, respectively) (Masters et al. 2002).  Snags may be created or consumed by fire.  An important consideration in prescribed burning when snag retention is a management objective is the fact that snags are 1,000 hr fuels.  Burning when these fuels have high moisture content (>25%) (Scott and Burgan 2005) or when the Keetch-Byram Drought Index (KBDI) is low will prevent consumption.

See also: Using Prescribed Fire to Manage Wildlife Habitat

Using Prescribed Fire to Control Insects and Diseases

Relatively few insects and diseases cause serious problems in shortleaf (Tainter 1986). The major threats include the southern pine beetle (Dendrococtonus frontalis) in the south and west, and littleleaf disease (associated with Phytophthora cinnamomi) in the eastern Piedmont states and across the mid-south (Campbell et al. 1953, Harlow and Harrar 1969, Tainter 1986, Zarnoch et al. 1994).  These two are potentially serious (Tainter 1986) especially in plantation stands and in overstocked stands under stress.

The Nantucket pine-tip moth (Rhyancionia frustrana) can be a serious problem in young plantation grown pines where sites have been mechanically prepared and particularly when in combination with herbaceous weed control (Tainter 1986).  Shortleaf stands that were naturally regenerated using fire have not been reported with serious incidences of this moth.

The southern pine beetle is by far the most injurious to shortleaf pine of all insects (Tainter 1986)(Figures 10-12).  Shortleaf are particularly susceptible when undergoing stress.  Outbreaks are common in overstocked stands, following lightning strikes, mechanical injury to the bark, excessive fire damage, extremely slow growth rates, drought stress, and the incidence of disease (Tainter 1986).  In particular, outbreaks of southern pine beetle may be associated with littleleaf disease (Campbell et al. 1953, Tainter 1986).  Control of stem density through low thinning (Smith et al. 1997) and introduction of prescribed fire on a 3- to 5-year cycle lowers the susceptibility of the stands to southern pine beetle attack (Stanturf et al.  2004). Maintaining high basal area stands of mixed loblolly-shortleaf pine stands at > 23 m²/ha (>100 ft²/ac) was found to increase losses due to bark beetle infestation (Cain and Shelton 2003a) and is presumed to be true for shortleaf as well.

Littleleaf disease was first recognized in 1934 in Alabama (Walker and Wiant 1966, Tainter 1986).  It has not been reported west of the Mississippi River.  This condition expresses itself in trees as young as 20 years of age but most commonly in 30 to 50 years of age (Campbell et al. 1953).  It has been associated with old-field natural stands and plantations established on previously intensively cultivated agricultural stands. The symptoms include short needles and overall reduced and yellow foliage with trees typically dying in 3–10 years. This condition is considered a disease by most authorities but has been termed a “decline phenomena” by others because of the unique combination of factors for symptoms to be expressed (Mueller-Dombois et al. 1983).  It occurs on nutrient deficient, poorly drained, and poorly aerated soils with high clay content or with clay subsoil, but is also associated with the soil fungus Phytophthora cinnamoni (Copeland and McAlpine 1955).  These combined factors evidently impede nitrogen uptake (Lawson 1990).  Symptoms may be alleviated with the application of high amounts of nitrogen (Lawson 1990).  Long term strategies have included retaining hardwoods within these stands because of benefits of hardwood leaf litter in improving soil conditions, and the exclusion of prescribed fire from these stands (Walker and Wiant 1966, Campbell et al. 1953).  However there is no direct evidence to suggest prescribed fire exacerbates this condition.  Selective breeding from progeny of resistant trees has shown some success (Zarnoch et al. 1994).

Annousus root rot (Heterobasidion annosum) is another problem in shortleaf but of lesser importance than the above (Tainter 1986).  Prescribed fire can be used to control this disease only somewhat (Froelich et al. 1978).  One other notable disease is red heart (Phellinus pinii) which generally occurs in trees older than 80 years (Tainter 1986).  While red heart is costly economically in that infected trees have little value for sawtimber use, it has tremendous benefit ecologically in areas identified for recovery of the endangered red-cockaded woodpecker because trees infected with this disease are selectively chosen as cavity trees by the bird (Jackson 1977).

See also: Using Prescribed Fire to Control Insects and Disease

Key Issues in the Implementation of Prescribed Burning

Prescribed fire is commonly used within shortleaf types as a silvicultural tool for hazardous fuel reduction, for ecosystem restoration, for management of competing hardwoods and herbaceous vegetation, for wildlife habitat management, to improve access, to enhance aesthetics, for improved grazing, to perpetuate fire-dependent species, and to maintain ecosystem health (Van Lear 1985, Masters 1991a, Wade 1989, Masters et al. 2003).  Frequent fire typically less than 12-year intervals on more exposed sites and less than 4-year intervals on better sites is essential to maintain shortleaf as a type.

The largest issue which looms in the implementation of prescribed fire is achieving prescribed fire targets both on public and on private lands (Palmer et al. 2004).  Part of this, in the case of public lands may be related to capacity of the organization to carry out burns but as with private lands it may be related to the will to carry out prescribed burns.  Even with our knowledge about the benefits of fire for ecosystem perpetuation, the application of fire on the land is not keeping up with what is necessary.  This leads to ecosystems that are departed from reference condition structure and function and ultimately are degraded (Schmidt et al. 2002).  On private lands lack of implementation of burns is often related to state and local regulations regarding burning.  It may also be related, in part, to the general apathy of landowners with respect to active forest management on their lands.  It is also related to the issue of strict liability for those conducting burns (Palmer et al. 2004).  As the wildland urban interface expands and urban areas encroach upon wildlands, many in the public are intolerant of smoke because of the perception of physical danger and potential health risks (Wade 1993, Palmer et al. 2004).  Although many landowners are less concerned with smoke management and public perception, these issues are important because it the public perception that dictates prescribed fire legislation.

Associated with this is the administration of the 1970 Clean Air Act by the Environmental Protection Agency (EPA) (Achtemeier et al. 1998).  This law limits the various types of pollutants that are acceptable in air across different regions of the country.  Of concern are the regional limits of particulate matter and carbon monoxide in smoke.  Currently the smoke from wildfire and from prescribed fire is viewed as equivalent by EPA when reported findings suggest otherwise (K. Robertson, Tall Timbers Research Station, personal communication).  Burn bans are increasingly being put in place in counties surrounding high urban populaces where air quality issues are paramount (Palmer et al. 2004).  Additional research is needed to arrive at standards that are acceptable for both the health of the citizenry and for the health of regional forests.

Another issue about implementation of prescribed burns is related to the current ecological debate over the appropriate season to burn.  Because of the recent push to burn in the growing season, managers may forego burning because of the fewer number of suitable burn days or the risk associated with burning during the growing season (Sparks et al. 1998, 2002; Glitzenstein et al. 2003).  As these authors have suggested fire in any season is preferable to no fire in fire-adapted or fire-dependent systems.  Fire frequency should take precedence over fire season when these two are at issue (Glitzenstein et al. 2003).  Where possible a mixture of both growing and dormant season prescribed fire at frequent intervals will insure perpetuation of shortleaf and associated species (Masters et al. 1995, 2005; Sparks et al. 1998, 1999, 2002).