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Vegetational changes due to prescribed fire in Mission Tejas State Park.

ABSTRACT. -- Park managers are faced with increasing use of recreation areas by the public, so careful management of the park's resources is required to prevent their degradation. Prescribed fire is a widely accepted method for managing and restoring natural ecosystems. Fire can be used to reduce the buildup of hazardous fuels, improve wildlife habitat, enhance aesthetic values, create a diversity of plant communities, and maintain endangered species. A prescribed burn was conducted at Mission Tejas State Historical Park in East Texas to evaluate the effects of prescribed fire on the ecological and aesthetic values of forest stands in the park. Pre-burn and post-burn analysis of sample plots indicated that the fire top-killed woody understory vegetation, but most hardwood species resprouted. Changes also occurred in forest floor coverage. After the fire, leaf litter and shrubs were reduced, while grasses and forbs increased. Overall stand density and diversity was increased, which should provide visitors with a quality recreation experience. Key words: prescribed fire, aesthetics, understory vegetation.

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In the last few decades, the demand for public outdoor recreation opportunities has increased rapidly. However, the supply of recreation facilities has generally not kept up with the increase in the number of visitors. Park visitors demand a wider variety of services and simultaneously insist on protection of natural ecosystems (Daniel, 1990). This has put a heavy responsibility on managers of parks and wilderness areas to provide adequate outdoor recreation opportunities while protecting their park's natural resources from degradation and decline.

Fire has long been recognized as an important component in natural ecostystems. Many plant communities are specifically adapted to survive fires, and some species, including endangered or threatened species, depend on periodic fire for their continued existence. It is obvious that most recreation areas cannot be left exposed to the damaging and potentially life-threatening effects of random, uncontrolled wildfires. Park managers have learned to use prescribed fire (set under exacting conditions of weather and fuel) to bring about changes in plant and animal communities to preserve the underlying processes of natural ecosystems.

Current fire terminology indicates a prescribed fire can be either initiated by managers or a natural fire occurring under specified conditions in selected wildland areas. A typical prescribed fire is one that is intentionally ignited by managers to accomplish specific objectives. A natural fire ignited by lightning may be allowed to burn so long as it stays within the agency's weather and fire behavior prescriptions. Both fire types are closely monitored to assure they meet management objectives.

BENEFITS OF PRESCRIBED BURNING

Some benefits can be derived from the use of prescribed fire as a park management tool. Fire provides these benefits effectively and with relatively low cost when compared to mechanical or chemical treatments.

Wildlife Habitat Improvement

Burning is highly effective in managing wildlife habitat. A mosaic of burned and unburned areas increases edge effect (transition) between different plant communities, promoting a varied population of wildlife to be enjoyed by visitors.

Burning opens up densely forested sites that develop in the absence of fire and results in an increase in the amount of grasses and sprouts that browsing animals, such as white-tailed deer (Odocoileus virginianus virginianus), feed upon (Wade and Lunsford, 1989; Fuller, 1991). Minerals and nutrients from burned forest fuels are released into the soil, which stimulates fruit and seed production, resulting in both a qualitative and quantitative increase in the food supply (Chandler et al., 1983). Ground-dwelling birds, such as wild turkey and bobwhite quail, generally benefit from fires because they can feed on vegetation that grows close to the ground in newly created openings.

Reduction of Hazardous Fuels

Probably the most important goal of prescribed burning is the reduction of forest fuels which tend to build up on the forest floor over time. Previous management policies have sometimes led to hazardous accumulations of fuel because of attempts to exclude all fire from forested environments. The situation is made even more serious by the increasing wildland-urban interface areas (caused by large numbers of people moving into forested areas) that expose more people and property to danger from wildfires. Because of the potential danger of fire escaping, some resource managers are reluctant to use prescribed fire to correct the imbalance of fuels. But these accumulating fuels will ultimately burn. Careful reintroduction of fire in the form of prescribed burning may be the only economical (practical) way to prevent catastrophic wildfires.

Enhancement of Aesthetic Values

Prescribed burning can be used to enhance a park's appearance to visitors by increasing diversity in the park landscape (Wade and Lunsford, 1989). Diversity of view helps to create a more pleasing visual mix of forest vegetation. For example, increased flowers and wildlife make open forest stands more interesting places for hiking. A mixture of burned and unburned stands increases the diversity of view and thus enhances the visual attractiveness of plant communities. Scenic vistas can also be created by burning, enabling the visitor to see interesting landscape features.

Maintain Fire-subclimax Species

Such diverse plant species as longleaf pine (Pinus palustris) and pitcher plants (Sarracenia sp.) benefit from an active prescribed burning program. Both the Nature Conservancy at Roy E. Larson Sandylands and the National Park Service at the Big Thicket National Preserve have used fire in the management of these and other plant communities (Reeves and Corbin, 1985).

POTENTIAL DISADVANTAGES OF PRESCRIBED BURNING

There are some effects from prescribed burning that may be considered unfavorable for recreational areas, but most of these impacts are relatively short-term. Park resource managers should consider these potential complications and take precautionary steps before a prescribed fire program is initiated.

Smoke and Air Quality

One of the more immediate effects of fire is the short-term degradation of air quality caused by smoke. Burning of organic materials releases water vapor, carbon dioxide, and particulate matter, and some of these compounds are emitted into the air (Reeves, 1977). Many areas have now passed laws that regulate or restrict burning with the intention of reducing air pollution. But the most objectionable effect of smoke in a recreational setting is that it reduces visibility. This effect can be minimized by conducting the prescribed burn in as short a time as possible and by avoiding burning during temperature inversions and other periods of high atmospheric stability (Reeves, 1972; Wright, 1982).

Deleterious Effects on Wildlife

Some species of wildlife can be negatively affected by fire. For example, ground nesting sites can be destroyed by a poorly timed prescribed burn. This problem can be minimized by planning prescribed burns when nesting activity has ceased and by providing ample escape routes for small mammals on the site.

Prescribed fire can also have adverse effects on fish habitat (Wade and Lunsford, 1989). Burning close to a stream or lake could result in silt and sediment entering the aquatic environment. If a fire removes the shading vegetation along a stream, water temperatures can increase to levels that are harmful to fish. Therefore, a buffer zone of litter and vegetation should always be left around riparian or stream-side areas to protect fish habitat.

Attitudes of Visitors

The ash and scorched trees left immediately after a fire can affect the perceived scenic beauty of a forest stand, but burned areas usually recover rapidly and vegetation often surpasses its pre-fire condition. The reaction of the public to the effects of burning depends largely on individual opinions and biases, the type of recreational activity being pursued, and the extent of interpretation efforts employed to inform park visitors. The interpretative efforts of park managers may be most important in shaping the attitudes of visitors toward burning and should be considered when developing a fire management plan.

In most cases, the benefits of using prescribed fire to manage vegetation resources in parks outweigh the negative effects. Although prescribed burning has been used in the past to manage forested recreation areas, more effort is needed to gain public approval for prescribed burning programs. This can best be accomplished by interpretive programs that explain the role of fire in forest ecosystems and park management. Also, additional research is needed to relate the ecological effects of fire to the quality of recreation experiences.

MISSION TEJAS PRESCRIBED FIRE PROJECT

In fall and winter of 1991, through a cooperative arrangement between Texas Parks and Wildlife Department (TPWD) and the College of Forestry at Stephen F. Austin State University (SFASU), a prescribed burning program was initiated at Mission Tejas State Historical Park, located in the Pineywoods vegetation region of East Texas. The park, containing 47.75 hectares, was purchased by local citizens in 1935 and transferred to the Texas Forest Service. The Texas Forest Service operated the park as a demonstration of good forest management practices and for recreational purposes. The park was transferred to the Texas Parks and wildlife Department in 1957. The TPWD is charged with protecting and preserving the natural and historical features within the park.

The park's forested area is an even-aged stand consisting of primarily loblolly pine (Pinus taeda) and shortleaf pine (P. echinata). This loblolly-shortleaf mixture is the most widespread forest cover type in the southern United States (Mann, 1980). Intermingled with the pines are a variety of hardwoods. The forest floor in most areas of the park was covered with a dense growth of understory vegetation that limited visibility and discouraged access by park visitors. In addition, the accumulation of unburned fuels over time presented an extreme fire hazard to historical structures, park developments, and neighboring private land.

The purpose of the prescribed fire project at Mission Tejas Park is to study the aesthetic and ecological changes caused by using fire to manage natural resources in a recreational setting. The results of the evaluation will be incorporated into an interpretive program that will be applicable in Texas state parks using prescribed fire. This interpretive program will be used to increase the public's knowledge of the role that fire plays in forest ecosystems and to promote the acceptance of prescribed fire as a sound park management practice.

Preparation for Burning

In 1991, park facilities and vegetation types were analyzed, and a 12 hectare section of the park was selected for the study. The following spring, randomly selected parts of the study area were prescribed burned (Fig. 1). Prior to the treatment, a fire management plan was developed. Also, 20 circular plots 1/40 hectare in size were established throughout the fire management area. Ten plots were selected to be burned while the remaining 10 plots remained unburned as controls. The centers of the circular plots were marked with a metal T-post. The area was divided so that burned and unburned sections were equally representative of the vegetation types in the study area, yet both burned and unburned areas would be visible to visitors driving or walking the park road.

A preliminary vegetation survey was conducted in fall 1991 to determine the species composition and density of the understory species in the stand before burning (Table 1). In each sample plot, the sample plot, the species and height of understory vegetation was recorded, and the plot was photographed from each cardinal direction to record vegetation density and visual aesthetics.

To prepare for the prescribed burn, SFASU personnel constructed fire lines with hand tools to control the spread of the fire and to protect areas that would remain unburned. The actual prescribed burn took place in early March, when atmospheric conditions and fuel moisture were within prescription. One of the major concerns of the fire crew during the prescribed burn was protecting the Rice Family Home, a historic log cabin located inside the area to be burned. Extra personnel were stationed around the structure with fire suppression equipment to protect the building.

Post-burn Vegetation Inventory

Four months after the prescribed burn, a second inventory was taken at the sample plots to determine changes in the vegetation composition since the prescribed burn. Since the initial survey did not reveal much variation in the vegetation complex between areas to be burned and those to be left for controls, it was assumed differences observed later primarily would be due to fire effects. The species and height class of each understory species that survived the fire and each sprout originating from plants that had been top-killed were recorded.

At this time, the overstory vegetation was also inventoried. All live trees with a diameter-at-breast-height (dbh) of five centimeters or greater at each plot were tallied. The species, total height, and dbh of each tree in the plots were recorded. Since overstories are seldom altered by a prescribed burn, we did not make a survey until after the first treatment.

To inventory the herbaceous vegetation on the forest floor, four subplots, each 0.2 [m.sup.2] in size, were established at the perimeter of each main plot. The frequency of woody species, vines, grasses, and forbs within the subplots was recorded. Also, the percent coverage of the following categories was recorded: shrubs, forbs, grasses, leaf litter, and bare soil. Shrubs included all woody perennials, grasses included herbaceous annual plants, and forbs included all other herbaceous species.

The relative and absolute density of each species of woody vegetation in the understory before and after the prescribed burn was calculated. The results of the two inventories were compared to ascertain any changes in vegetative composition caused by the fire. In addition, the relative and absolute frequency of herbaceous species was determined, and the changes in species composition and frequency between the burned and unburned areas compared.

[FIGURE 1 OMITTED]

RESULTS AND DISCUSSION

Effects on Understory Woody Vegetation

The pre-burn inventory of woody vegetation showed that the most common species in the understory were loblolly and shortleaf pine, with an average of 7,030 seedlings per hectare (Table 2). The second most common species was rusty blackhaw (Viburnum rufidulum), a hardwood understory species. Other common species (over 40 stems per hectare) included American beautyberry (Callicarpa americana), eastern redbud (Cercis canadensis), sweetgum (Liquidambar styraciflua), yaupon (Ilex vomitoria), vaccinium (Vaccinium spp.), and various species of oaks (Quercus spp.) and hickory (Carya spp.). The total number of woody stems per hectare in the understory was 17,185 before the prescribed burn.

After the prescribed burn, differences in the composition of understory vegetation could be observed between the burned areas and unburned areas within the fire management zone. In the burned areas, the number of pines dropped significantly after the fire. Most of the pine mortality consisted of small seedlings less than three meters in height and smaller than five centimeters in diameter that had not yet developed resistance to fire.

The tops of almost all young hardwoods up to three meters were killed by the fire. Hardwoods generally are much more susceptible to fire injury due to the lack of thick, fire-resistant bark. However, most of the understory hardwood species sprouted readily, and the sprouts of some species, such as yaupon, were so numerous that the toatl number of stems present after the fire greatly exceeded their pre-burn density. The most successful sprouting species in the burned areas were yaupon, various oaks, eastern redbud, and rusty blackhaw (Table 2). Total density for all species nearly doubled the pre-burn density.

In the unburned areas of the fire management zone, the total density of understory vegetation, at 27,730 stems per hectare, was only slightly less than in the burned areas, but the species composition and density distribution was quite different. A comparison of the species present in the unburned areas with those in the burned areas indicates that the overall understory diversity increased where fire had been used. As in the pre-burn sample plots, the understory of the unburned areas was dominated by pine seedlings, with oaks, rusty balckhaw, and American beautyberry accounting for the majority of additional stems.

The predominance of pine seedlings in the understory of the unburned areas may reflect good regeneration potential due to an especially large seed crop in 1991. Most of the small pine seedlings had not developed secondary needles. Therefore, many of these seedlings apparently germinated after the pre-burn survey, which could account for the smaller proportion of pine seedlings in the pre-burn data.

Effects on Forest Floor Coverage

An analysis of the forest floor after the prescribed burn showed changes in the percent ground coverage in all categories. In the unburned areas, leaf litter covered the greatest percentage of the forest floor, followed by woody shrubs (Table 3). Together these categories accounted for almost 85% of the ground cover. Herbaceous plants occurred somewhat infrequently, and exposed soil was rare. The large amount of pine needles in the litter layer was due to the pine overstory. Shade caused by the combination of overstory trees and dense understory vegetation along with the litter layer hindered the growth of many herbaceous plants which require direct sunlight and limited competition to grow properly.

In the burned areas, the percent coverage by leaf litter decreased by 11.2%, as would be expected after a fire (Table 3). However, much of the burned area was covered with litter of newly fallen leaves and pine needles following the fire.

Coverage by shrubs decreased by nearly 40%, an indication that low woody species had not fully recovered after being top-killed by the fire. Forbs and grasses showed modest increases in coverage. The major limiting factors were apparently shade and the litter layer (which in some areas was not reduced sufficiently by the fire to allow establishment of herbaceous species).

Implications for Park Management

One of the most important effects of the prescribed fire at Mission Tejas State Park was the reduction in the amount of hazardous fuels in the forest stand. The buildup of fuels around the historic Rice Family Home was a cause of concern, because an uncontrolled fire could have easily destroyed the structure. The area around the cabin has now been made more open by the fire and some mechanical clearing, making it much easier for visitors to walk around and explore the structure.

The increase in diversity of woody species following the fire indicates that many species respond well to prescribed burning. If a park manager wished to maintain a diversity of plant species, a mosiac of burned and unburned areas would provide a variety of site characteristics needed to satisfy the ecological requirements of many species. Regular periodic burning would help prevent the return of dense vegetation on selected areas of the park.

The reduction of understory vegetation by the fire also opened up the forest stand, allowing greater visibility from the main park road and the nature trails. It improved wildlife habitat in the fire management area where top-killing of understory vegetation encouraged prolific sprouting, which in turn attracted browsing species such as white-tailed deer. Seed- and fruit-eating birds may find more food among the various grasses and shrubs, especially where crown canopies were more open and litter competition was reduced. However, the production from some fruiting shrubs and small trees may be reduced temporarily as they were top-killed by the fire. Regular prescribed burning for a few years would help keep the woody species suppressed enough to increase the flowering herbaceous component on the forest floor.

The openness of the forest stand, combined with the mature pine overstory, may encourage its use by the red-cockaded woodpecker (Picoides borealis), a bird native to East Texas and listed by the U.S. Fish and Wildlife Service as an endangered species. The red-cockaded woodpecker thrives in open, mature pine stands which have minimal hardwood understory/midstory. In the future, some parks may play an increasing role in the management and restoration of endangered species, making prescribed fire an essential management tool.

CONCLUSION

The on-going prescribed fire project at Mission Tejas State Park helps demonstrate the effectiveness and desirability of fire in managing the natural resources of recreation areas. As the land base of natural areas continues to shrink, parks will play an important part in providing areas where natural ecosystems can operate. As the number of visitors to parks continues to increase, it will become even more important for resource managers to apply sound management methods to protect natural ecosystem processes. Prescribed fire is an excellent choice for enhancing ecological values of parks, while still providing a quality recreation experience for the public.
TABLE 1. List of woody understory species found in the fire management
zone.

Species Common name

Acer rubrum red maple
Baccharis halimifolia eastern baccharis
Bumelia lanuginosa gum bumelia
Callicarpa americana American beautyberry
Carpinus caroliniana American hornbeam
Carya spp. hickory
Celtis laevigata sugarberry
Cornus florida flowering dogwood
Diospyros virginiana persimmon
Fraxinus americana white ash
Gleditsia triacanthos honeylocust
Ilex opaca American holly
Ilex vomitoria yaupon
Juniperus virginiana eastern redcedar
Liquidambar styraciflua sweetgum
Magnolia virginiana sweetbay
Morus rubra red mulberry
Nyssa sylavatica black tupelo
Ostrya virginiana eastern hophornbeam
Pinus spp. pine
Prunus caroliniana Carolina laurelcherry
Prunus serotina black cherry
Quercus spp. oaks
Rhus copallina shining sumac
Sassafras albidum sassafras
Ulmus alata winged elm
Vaccinium spp. vaccinium
Viburnum rufidulum rusty blackhaw

TABLE 2. Density distribution of common woody species (50 stems per
hectare or more) occurring in the fire management zone before and after
prescribed burning.

 Stems/hectare
 Pre-burn Post-burn
Species Burned area Unburned area

Callicarpa americana 2063 1093 2745
Carya spp. 247 766 220
Celtis laevigata 0 0 56
Cercis canadensis 556 4769 0
Cornus florida 185 642 413
Diospyros virginiana 0 148 54
Fraxinus americana 136 840 0
Gleditsia triacanthos 0 99 27
Ilex opaca 37 0 166
Ilex vomitoria 297 7487 961
Juniperus virginiana 49 0 54
Liquidambar styraciflua 482 1408 371
Magnolia virginiana 0 49 0
Morus rubra 0 0 82
Ostrya virginiana 0 0 109
Pinus spp. 7030 1285 12602
Platanus occidentalis 124 0 0
Prunus caroliniana 0 0 329
Quercus spp. 1903 6548 5024
Rhus copallina 136 1334 193
Sassafras albidum 161 1384 467
Ulmus alata 136 371 301
Vaccinium spp. 395 1581 109
Viburnum rufidulum 3237 3237 3855
Total 17186 36348 27730

TABLE 3. Percent forest floor coverage by vegetation and soil components
in burned and unburned areas of the fire management zone.

Forest floor component Unburned plots Burned plots

Shrubs 26.2 15.8
Forbs 3.8 7.3
Grasses 8.5 11.0
Leaf litter 58.7 47.5
Bare soil 2.8 18.4
Total 100.0 100.0


LITERATURE CITED

Chandler, C., P. Cheney, P. Thomas, L. Trabraud and D. Williams. 1983. Fire in forestry, volume 1: forest fire behavior and effects. John Wiley and Sons, New York, 450 pp.

Daniel, T. C. 1990. Social/political obstacles and opportunities in prescribed fire management. Pp. 134-138, in Effects of fire management on southwestern natural resources (J. S. Kramme, tech. coord.), USDA Forest Serv. Gen. Tech. Rep. RM-191, Fort Collins, Colorado, 293 pp.

Fuller, M. 1991. Forest fires: an introduction to wildland fire behavior, management, firefighting, and prevention. John Wiley and Sons, New York, 238 pp.

Mann, W. F., Jr. 1980. Loblolly pine--shortleaf pine. P. 56 in Forest cover types of the United States and Canada. Soc. Amer. Foresters, Washington, D. C., 148 pp.

Reeves, H. C. 1972. Minimizing air pollution due to prescribed burning. The Consultant, 17:1-5.

______. 1977. Use of prescribed fire in land management. J. Soil and Water Conserv., 32:102-104.

Reeves, H. C., and D. Corbin. 1985. Fire and the Big Thicket. Texas Nat. Hist., 1:23-26.

Wade, D. D., and J. D. Lunsford. 1989. A guide to prescribed fire in southern forests. USDA Forest Serv. Tech. Pub. R8-TP11, Atlanta, 56 pp.

Wright, H. A., and A. W. Bailey. 1982. Fire ecology, United States and Canada. John Wiley and Sons, New York, 501 pp.

RICK L. TURNER, HERSHEL C. REEVES, AND MICHAEL H. LEGG

College of Forestry, Stephen F. Austin State University, Nacogdoches, Texas 75962
COPYRIGHT 1994 Texas Academy of Science
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1994 Gale, Cengage Learning. All rights reserved.

 
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Author:Turner, Rick L.; Reeves, Hershel C.; Legg, Michael H.
Publication:The Texas Journal of Science
Geographic Code:1U7TX
Date:Feb 1, 1994
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