Opuscula Philolichenum, 7: 101-120. 2009
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Opuscula Philolichenum, 7: 101-120. 2009. Lichens and Related Fungi of Pine Bluff Arsenal, Arkansas 1 DOUGLAS LADD ABSTRACT. – A total of 161 taxa of lichens and related fungi were documented from Pine Bluff Arsenal in Jefferson County, on the Gulf Coastal Plain in south-central Arkansas. Constrained time entitations in five natural area units within the arsenal revealed a high degree of similarity among the lichen biota of the units. Crustose lichens are the most common growth form, comprising nearly 60% of the lichen diversity at the site. The lichen biota of the Pine Bluff Arsenal has strong biogeographic affinities to the southeastern coastal plain, including western range extensions for sev- eral coastal plain species. INTRODUCTION Pine Bluff Arsenal encompasses 14,944 acres (5,978 ha) along the west side of the Arkansas River in Jefferson County, south-central Arkansas, north of the town of Pine Bluff. Established in 1941, the facility has provided various manufacturing, storage and dismantling functions for specialty munitions and chemical weapons. Most of the site lies within the West Gulf Coastal Plain ecoregion, although some of the low wetlands and riparian areas fall within the Mississippi River Alluvial Plain ecoregion (TNC 1999). The site consists of a mix of flat lowlands and moderately dissected low rolling uplands, with a total elevational relief of 145 feet. Some steep soil banks with generally eastern exposure occur along the Arkansas River and Yellow Lake. Detailed descriptions of the site, its physical features, and vascular vegetation are provided by Campbell et al. (1997). Despite a long history of disturbance associated with military use, more than 10,000 acres (4046 ha) of the tract is forested. These woodlands range from hardwood and pine-hardwood stands in the uplands to bottomland hardwoods in the poorly drained sites, and a few wetlands with old growth Bald Cypress (Taxodium distichum). Dominant trees in the uplands include Loblolly Pine (Pinus taeda), Shortleaf Pine (Pinus echinata), White Oak (Quercus alba), Post Oak (Q. stellata), and Southern Red Oak (Q. falcata). In addition to Bald Cypress, trees of more mesic and wet sites include Sweetgum (Liquidambar styraciflua), Water Oak (Quercus nigra), Willow Oak (Q. phellos), Green Ash (Fraxinus pennsylvanica), Beech (Fagus grandifolia), Sugarberry (Celtis laevigata), Box Elder (Acer negundo), Hornbeam (Carpinus caroliniana), and Bitternut Hickory (Carya cordiformis). METHODS Most field work for this project was conducted in December 1999 (Ladd 2000). Attempts were made to survey all habitats and substrates throughout non-restricted portions of the Pine Bluff Arsenal. To assess the equability of lichen distribution within the arsenal property, and to ensure the completeness of the survey, detailed lichen inventories were compiled for five natural area units within the site, spending approximately equal area-corrected survey time in each unit (minimum 0.5 person days/unit). Four of these units, the Phillips Creek, Refuge Woods, Tripletts Bluff, and Yellow Lake units, are the same as those described in Campbell et al. (1997). The Eastwood Bayou unit is immediately east of the unit described in Campbell et al. (1997). Attempts were made to investigate all habitat types and substrates within each unit. All lichens observed in each unit were recorded, along with substrate information and qualitative observations of abundance. A lower intensity of survey effort was also directed to areas outside of the natural area units, in an attempt to assess as many potential habitats, substrates, and landscape conditions as possible. Where appropriate, acetone extracts of lichens were chromatographed on Whatman K6 60Å 250μm silica gel coated 10 Η 20 cm glass plates using the three solvent system of Culberson and Kristinsson (1970), with the methyl tert- butyl ether substitution modification in solvent B (Culberson & Johnson 1982). 1 DOUGLAS LADD – The Nature Conservancy, 2800 S. Brentwood Blvd., St. Louis, MO, 63144, USA. – e-mail: [email protected] 101 RESULTS AND DISCUSSION I. – DIVERSITY A total of 161 taxa of lichens and related fungi, including some unnamed species, have been documented from Pine Bluff Arsenal. This level of lichen diversity is less than would be expected for an equivalent area in the Ozark region, which is one of the few areas in midcontinental North America for which within-site lichen diversity is available. Lichen diversity at the arsenal is likely constrained by both the lack of saxicolous substrates and the long history of intensive land use, including farming prior to establishment of the arsenal. For comparison, Ladd (1996) documented 201 lichens from two forest units totaling 1,231 acres (492 ha) in the northern portion of the Missouri Ozarks, although 62 (31%) of these taxa were obligately saxicolous. Wetmore (1992) reported 179 lichens from Hercules Glades Wilderness, a 12,315 acre (4,926 ha) wilderness area in southwestern Missouri. Again, at least 37 (21%) of the taxa in Wetmore’s report are obligately saxicolous. Thus the non-saxicolous diversity known from Hercules Glades Wilderness is lower than that for that of Pine Bluff Arsenal, an area of approximately similar size. Ladd and Grabner (1998) reported more than 250 lichens from the nine units of the Missouri Ozark Forest Ecosystem Project, encompassing some 9,400 acres (3,760 ha) in the southeastern Missouri Ozarks. All of these areas, however, have well-developed saxicolous substrates, greater microhabitat diversity, and a less intensive and environmentally severe land use history. Thus, given the paucity of saxicolous substrates and the past disturbance history of the area, the presence of 161 taxa of lichens at Pine Bluff Arsenal is significant, and represents a diverse cohort of lichens. As shown in Table 1 (below), coefficients of similarity reveal that the lichen biota among the five natural area units is compellingly similar. Even more compelling is the uniform variance displayed by the narrow range of similarity coefficients among the lichens of any pair of units, ranging only from 0.67 to 0.73. Forty-seven (30%) of the lichens are common to all five units, and an additional 21 (14%) are known from four units. Site (lichen taxa) YL TB RW PC Eastwood Bayou (76) .68 .73 .69 .73 Phillips Creek (92) .70 .73 .67 Refuge Woods (95) .69 .68 Tripletts Bluff (92) .70 Yellow Lake (102) Table 1. Coefficients of similarity among the lichen biota of natural area units within Pine Bluff Arsenal. With the exception of the Eastwood Bayou unit, the lichen biota of each of the survey units has a similar level of diversity of about 100 lichen taxa. The significantly lower diversity of the Eastwood Bayou unit probably results from a combination of less survey time and more anthropogenically disrupted habitat, including large areas of former farmland. Forty-one (26%) of the lichens are known only from a single unit. Most of these are uncommon lichens of minor importance from a dominance or cover perspective. Fourteen of these are known only from the Refuge Woods unit, eleven are known only from the Yellow Lake unit, nine are known only from the Tripletts Bluff unit, and seven occur only within the Phillips Creek unit. There were no lichens unique to the Eastwood Bayou unit. II. – PHYSIOGNOMY A majority of the lichens of Pine Bluff Arsenal are crustose (Table 2, below). This parallels physiognomic profiles from elsewhere in North America: Ladd (1996) reported a similar distribution of physiognomic types from woodlands in the northern Ozarks of Missouri, with 65% of the lichens crustose, 25% foliose, and 9% fruticose. A study of the lichens of a small preserve in southwestern Connecticut (Ladd et al. 2009) was also similar in pattern of lichen physiognomy: 59% crustose, 26% foliose, 15% fruticose. It is interesting to speculate whether this ratio among physiognomic classes prevails throughout intact habitats in eastern and central North America. The low diversity of 102 gelatinous lichens at Pine Bluff is likely due to past land use history and the sensitivity of many gelatinous lichens to both habitat perturbation and air pollution. The former clearing of much of the Pine Bluff site, and the presence of a large pulp mill immediately to the south, have both undoubtedly impacted the local biota, including the lichens. Physiognomy # of taxa % of flora Crustose 96 59.6 Foliose 45 28.0 Fruticose 20 12.4 Table 2. Physiognomic profile of the lichens of Pine Bluff Arsenal III. – SUBSTRATES AND HABITATS At Pine Bluff Arsenal, primary substrates available to lichens are trees and, to a lesser extent, soil, and lignin. There are extremely limited occurrences of saxicolous substrates associated with poorly consolidated sand and siltstones in soil exposures, as well as some weathered old concrete bridges and culverts. Bryophytes are locally abundant, but muscicolous lichens are rare at the site. Lichens are widely distributed on almost every available substrate throughout all portions of the arsenal that were surveyed, except for mowed open lawn expanses and high usage areas surrounding buildings and other facilities. In some of the more heavily overgrown or younger secondary timbers, lichens were not as abundant as in more mature and open woodlands, but all woodlands had a pervasive lichen presence. Corticolous lichens dominated the site diversity, with 126 lichens (87% of the biota). Fifteen lichens (10% of the biota) occurred on lignin, which consisted primarily of decorticate stumps and logs of oaks and pines. Twelve lichen taxa (8% of the biota) were terricolous; these occurred primarily on exposed to lightly shaded, stable, well-drained soil embankments above flood levels along streams and in association with established cultural features such as ditches and dikes. Despite the near absence of saxicolous substrates, eight taxa (5% of the biota) inhabited the sparse, small sedimentary fragments found in a few soil embankments, and on weathered concrete of bridges, culverts, and abutments.