Effects of prescribed fire on the composition of woody plant communities in southeastern Texas

Abstract

Abstract. The response to prescribed burning of plant communities ranging from dry to wet habitats was monitored using permanent plots sampled from 1989 to 1993. Temporal controls for fire effects were provided by matched sets of plots protected from fire by newly constructed fire breaks. Changes in species composition were studied by ordination of strata of trees (> 5 cm DBH), small trees (2–5 cm DBH), large saplings (1–2 cm DBH), and small saplings and seedlings (50–140 cm tall). Results show that changes occurred largely in the small tree stratum, in which xeric species increased in importance. Although there were changes in sapling and seedling strata, no clear direction of change was recognized. Fire had little effect on the tree stratum. Of the seven community types under study, three types, sandhill, upland pine, and upperslope pine‐oak, were most strongly affected, as indicated by post‐fire change in positions of samples representing these communities in ordination space and reduction in understory species abundance. Samples representing the other four mesic and wet communities showed little or no change in their positions. These short‐term results indicate that changes in vegetation resulting from fire were small and were mostly restricted to the dry types in which possible compositional change is expected to occur. This differential effect of fire suggests that the influence of fire is secondary to that of topographical and soil gradients in determining vegetation pattern under current fire regimes. Fire seems to reinforce an overall vegetation gradient controlled by soil in southeastern Texas.

Land use effects on groundlayer composition and regeneration of mixed pine hardwood forests in the Fall Line Sandhills, S.E. USA

“…Differences in groundlayer composition developed between 2-year and 4-year fire sites after 2 years; composition of the 2-year stands was similar to that of stands with heavier military use and clayey soil, while composition of the 4-year stands was similar to that of stands with lighter military use and sandy soil. An increase in legumes, grasses, and pines, and decrease in fire-susceptible hardwoods and forbs, has been shown in other frequently burned southeastern forests (Waldrop et al, 1992;Liu et al, 1997;Beckage and Stout, 2000;Provencher et al, 2001), but we could find no examples of pronounced composition shifts in response to a short-term change in the customary fire frequency. The patchy soils, topography, vegetation, and land use at Fort Benning may allow species of diverse fire tolerances to persist at the landscape-level and provide a rapid regeneration pool in sites with changes in the fire return interval.…”

“…Throughout the southeastern US, prescribed fire has been implemented to restore pine dominance, and especially longleaf pine (Pinus palustris) savanna, on appropriate sites (e.g., Jones and Davo, 1997). Historically, longleaf pine communities on the southeastern Coastal Plain were maintained by frequent fires, which slow succession to less firetolerant hardwoods and promote open canopy and a groundlayer rich in graminoids and legumes (Waldrop et al, 1992;Liu et al, 1997;Provencher et al, 2001). Considered more desirable and more tolerant than hardwoods and co-occurring pines (e.g., Pinus taeda, loblolly, and P. echinata, shortleaf), longleaf may become relatively more abundant with frequent fire, drought, and impoverished soil (Beckage and Stout, 2000;Collins et al, in press).…”

Responses to Prescribed Fire at Big Thicket National Preserve, Texas, USA

“…In the reference of Liu et al [21], treatments reduced small tree densities immediately post burn, with minimal effects in the wetter vegetation types of midslope, lowerslope, and wetland savanna. Small tree data initially showed distinction among the wetland savanna and sandhill types, with the other types overlapping; over time the upperslope and midslope types became more distinct.…”

“…Plots can then be visualized on a two-dimensional projection according to their centroids to identify locations that have similar species compositions. CCA has been used to examine the temporal change in vegetation in relation to the prescribed burns in southeast Texas, including plots established at Big Thicket National Preserve [21]. Species abundance was used to compare differences in the vegetation communities.…”

“…Pine litter and the herbaceous vegetation carry fire well. However, hardwood invasion due to fire suppression can lessen the intensity of subsequent fires and result in further proliferation of hardwoods and recommended high intensity summer fires to combat hardwood invasion, but concluded winter burns have similar benefits to summer burns depending on management objectives [21][22][23].…”