Effects of prescribed burning on vegetation and fuel loading in three east Texas state parks.

Abstract. -- This study was conducted to evaluate the initial effectiveness of prescribed burning in the ecological restoration of forests within selected parks in east Texas. Twenty-four permanent plots were installed to monitor fuel loads, overstory, sapling, seedling, shrub and herbaceous layers within burn and control units of Mission Tejas, Tyler and Village Creek state parks. Measurements were taken during the summers of 1999 and 2000. Prescribed burning was conducted between these sampling periods in early spring 2000. Results indicated that the current applications of prescribed burning do not significantly influence vegetation or fuels. Sustained drought, prior management practices and imposed local burn bans reduced the window within which prescribed burns could be applied, and limited the effectiveness of the burns.

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Historically, fire has played an important role in most terrestrial ecosystems. Fire has an influence in such ecosystem components as recycling of nutrients, regulating plant succession and wildlife habitat, maintaining biological diversity, reducing biomass, and controlling insect and disease populations (Mutch 1994).

When conducted properly, prescribed fire undoubtedly alters the composition and structure of the understory vegetation within forests. Several subclimax communities and endangered species of Texas are dependent on fire. For example, fire is an essential element in the restoration and management of longleaf pine (Pinus palustris Mill.) stands and pitcher plant (Sarracenia alata Wood) wetland ecosystems. These and other communities benefit from an active prescribed burning program (Reeves & Corbin 1985).

Prescribed burning is currently used as a management tool in several Texas state parks for the purposes of reducing forest fuels, improving wildlife habitat, altering the composition and structure of the understory vegetation and enhancing park appearances. This study was conducted to evaluate the initial effectiveness of prescribed burning in the ecological restoration of forests and consisted of monitoring pre- and post-burn vegetative characteristics and fuel loads at three Texas state parks. At Mission Tejas State Historical Park, Tyler State Park and Village Creek State Park, 24 plots, eight in each park, were monitored in the summers of 1999 and 2000 to determine short-term ecological effects of pre-scribed burning on vegetation and fuel loads.

METHODOLOGY

The three parks surveyed in this study were all part of the Piney-woods Region of Texas Parks and Wildlife Department's Parks and Historic Sites. Mission Tejas and Tyler State Parks had similar ecological characteristics. Typical overstory species within the burn units of these parks included shortleaf pine (Pinus echinata Mill.), loblolly pine (Pinus taeda L.), sweetgum (Liquidambar styraciflua L.), water oak (Quercus nigra L.), white oak (Q. alba L.), mockernut hickory (Carya tomentosa (Poir.) Nutt.), white ash (Fraxinus americana L.) and American holly (Ilex opaca Ait.). Common understory species included yaupon (Ilex vomitoria Ait.), flowering dogwood (Cornus florida L.), American beautyberry (Callicarpa americana L.), longleaf uniola (Chasmanthium laxum var. sessiliflorum (L.) Yates), panicums (Panicum sp.) and various sedges (Texas Parks and Wildlife 2000a; Texas Parks and Wildlife 2000b).

Average low temperatures in January range from 0 to 2[degrees]C, while July averages highs of 34 to 36[degrees]C. The first and last freezes typically occur around mid to late November and mid March to early April, respectively. Average rainfall exceeds 100 cm per year (Texas Parks and Wildlife 2000a; Texas Parks and Wildlife 2000b). Steep slopes abound in these parks, with elevation changes of 100 m within both parks (Texas Parks and Wildlife 2000a; Texas Parks and Wildlife 2000b; Robinson & Blair 1997). The historic fire return interval where these parks are located was 4 to 6 years. It is presently greater than 20 years (Jurney 2000) due to suppression, fragmentation and urbanization of the surrounding areas. Heavy fuel loads persist throughout the park due to decades of sporadic use of fire.

Unlike the others, Village Creek State Park included cypress swamps, bottomland wetlands and blackwater sloughs in the flood plain of the Neches River. The burn unit was once a longleaf/little bluestem (Schizachyrium scoparium (Michx.) Nash.) stand. Due to fire exclusion it was being overtaken by broadleaf trees, such as water tupelo (Nyssa aquatica L.), river birch (Betula nigra L.), water oak and redbay (Persea borbonia (L.) Spreng.), in addition to the invasive Chinese tallowtree (Sapium sebiferum (L.) Roxb.). Common understory vegetative species included yaupon, flowering dogwood, American beautyberry, poison ivy (Toxicodendron radicans (L.) Kuntze), little bluestem, panicums and various sedges. The park's mean elevation was 7 m. January's average low temperature was 3[degrees]C, while July's average high was 34[degrees]C (Texas Parks and Wildlife 2000c). Historic fire return interval in the area was 1 to 3 years. Now it is greater than 20 years (Jurney 2000).

Methods for establishing plots, and sampling vegetation and fuel loads were as defined in the National Park Service Western Region Fire Monitoring Handbook (Western Region Prescribed and Natural Fire Monitoring Task Force 1992). Plot size and sampling locations varied for each monitoring …