ABSTRACT Vegetation at couple dry...

ABSTRACT

Vegetation at couple dry sandstone barrens in bishop of rome County, Illinois was sampled to provide baseline data forward composition, structure, diversity, and species-abundance patterns for comparison with vegetational changes resulting from applications of prescribed fire. Permanent outlines were established at both sites. Data were garner uped from canopy, subcanopy/shrub, and ground-cover strata. single in kind site, Gibbons Creek Barrens, is the fire treatment site while the other, Forest Service Barrens, be subservient tos as a fire-free control site. The vegetation at these barrens remnants is similar in many regards facilitating their use as treatment and have the direction of units for experimental study of fire powers Both sites are dominated earnestly in the canopy by Quercus stellate Wangh. The subcanopy shrub/sapling stratum is dominated by dint of Ulmus alata Michx.; however, several other taxa are usual to occasional. Size-class distribution of over-story tree remind ofs a pattern of change characterized by way of stand closure as recruitment of Quercus stellata and Ulmus alata alters the explain barrens structure. Patterns of subcanopy recruitment and tree size-class distribution support an interpretation of sites that are compositionally stable and structurally unstable in the over-story.

The same six ground-cover species are the mostly abundant species at both sites; however, rank abundance differs. At Gibbons cove Barrens the dominant herbaceous species is the C^sub 4^ prairie grass Schizachyrium scoparium (Michx.) Nash. while at Forest Service Barrens the dominant species is the C^sub 3^ thirsty woodland grass Danthonia spicata (L) Beauv. Ground-cover species are distributed in somewhat discrete patches with C^sub 4^ grasses occurring in interpret areas, C^sub 3^ grasses and reeds more generally distributed but predominating in more clos areas, and several spread woodland species occurring in the barrens verges and where Q. stellata is in relatively gentle abundance. Ground-cover species diversity is correlated inversely with density of Quercus stellate. Stand areas exceeding about 25 tree by 0.05 ha particularly have lower diversity suggesting a benchmark for vegetation management designed for maintaining vegetational diversity. one as well as the other sites appear to be high-quality natural areas, support a rich assemblage of native species, and lack an adventive flora.

INTRODUCTION

Barrens are rare, heterogenous, savanna-like communities resulting from a place of environmental conditions that, in the region of the prairie-forest transition belt in the Midwest, limit or retard forest disclosure (Heikens and Robertson 1994). These environmental conditions include dry-to-xeric soil moisture conditions, xeric south-to-southwestern fronts nutrient-poor habitats, grazing, and fire. Removal of individual or more of these special conditions can lead to dramatic changes in form composition, and diversity. All the listed factors historically have been important in the maintenance of barrens habitats in southern Illinois (Heikens 1991 Heikens and Roberston 1995) However, the same of the abiotic factors, fire, nearly has been eliminated from the ecosystem and vegetational changes, equal in dry barrens habitats, apparently are underway (Taft 1997)

A major characteristic of barrens is the personality of many herbaceous species typical of tallgrass prairie and ecotonal habitats intermediate between prairie and forest. Ground-cover species diversity is inversely correlated with tree density in employment oak flatwoods (Taft et al. 1995); as tree encroach forward the barrens, it is likely this also will lead to a decline in diversity, particularly among the rich prairie/savanna ground-cover species. Because of the rarity of barrens, their apparent decline and isolation, and the rich species diversity characteristic of the habitat, there is considerable interest in conservation, management, and restoration of barrens. Consequently data are stand in want ofed on the structure, composition, and diversity patterns of remnants to aid in their identification and in assessing their sustainability. as it was baseline data, when collected from permanent sample projects as in this study, also oblige as benchmarks for comparison following restoration efforts.

This paper describes the composition, arrangement of parts and diversity characteristics of the vegetation that existed at pair dry barrens remnants, Gibbons inlet Barrens (GCB) and Forest Service Barrens (FSB) prior to applications of prescribed fire at GCB Fire management commenc in the dormant season following baseline data collection and the vegetational replication to fire was evaluated for three and sum of two units years, respectively, following each of brace fires (Taft 1999, Taft in prep)

Gibbons inlet Barrens and the nearby Forest Service Barrens were pitch uponed for study because: 1) barrens popularly are rare community types that in many regions have not received adequate descriptive or experimental consideration to gain sufficient insights into their biotic composition and ecology 2) GCB is considered common of the highest quality (i.e., high ecological integrity) barrens remnants in Illinois (White 1978) and thus could be considered as somewhat representative of the presettlement condition, 3) fire is an important management tool for the maintenance of barrens, nevertheless few intensive or medium to long-term studies of the forces of fire on barrens vegetation have been waysed in the Midwest, particularly in Illinois, and 4) plans to implement prescribed fire at GCB a site concedeed by The Nature Conservancy, coincided with the site-selection proces for the cogitation of post-fire effects on barrens vegetation. Because of the community restoration objectives at GCB where fire was prescribed as a treatment for the entire barrens area (approximately three hectares) and adjoining clos woodland habitat, a separate sway site was required. The FSB (fire-free curb area) occurs on a nearby unit of the Shawnee National Forest (Figure 1)