Transactions of the Illinois State Academy of Science received 5/15/98 (1999), Volume 92, 1 and 2, pp. 37-51 accepted 8/25/98 Vascular Flora of Chauncey Marsh Natural Area, Lawrence County, Illinois Loy R. Phillippe1, Jennifer A. Tate2, David M. Ketzner1, and John E. Ebinger1 1Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820 2Department of Botany, The University of Texas at Austin, Austin, Texas 78713-7640 ABSTRACT The vascular flora of the Chauncey Marsh Natural Area, Lawrence County, Illinois was studied during the 1994 to 1996 growing seasons. A total of 351 taxa were found: five fern and fern-allies, 101 monocots, and 245 dicots. The families with the largest number of taxa include the Poaceae with 48 taxa, the Asteraceae with 33 taxa, and the Cyperaceae with 30 taxa, of which 20 were members of the genus Carex. An overstory analysis of the second growth wet-mesic floodplain forest that occurs on the site was also undertaken. In this forest, tree density averaged 353 stems/ha, with an average basal area of 28.5 m2/ha. Carya laciniosa (Michx.) Loud. (kingnut hickory) ranked first with an importance value (IV) of 44.9 (out of 200). Associated species included Liquidambar styraciflua L. (sweet gum), Quercus palustris Muenchh. (pin oak), Acer saccharinum L. (silver maple), and Ulmus americana L. (American elm), all with IV’s >15. INTRODUCTION Chauncey Marsh is an extensive wetland about four miles east of Chauncey, Lawrence County, Illinois. The marsh is located on an old ox-bow of the Embarras River, and is the largest marsh remaining in the Illinois portion of the Wabash River basin. The site contains an outstanding example of marsh and bottomland forest that was typical of this region at the time of European settlement. Elevation is from 130-133 meters above sea level. Chauncey Marsh is recognized by the Illinois Natural Areas Inventory of White and Madany (1978). It is located in the Chauncey Marsh Natural Area (CMNA) and is a dedicated Nature Preserve. Though subjected to some disturbance, including drainage attempts, the marsh still contains a relatively high diversity of plant and animal life. Ebinger (1982) found 165 taxa of vascular plants growing within the marsh community. Within the CMNA five major plant communities occur. The cultural communities are represented by prairie plantings, successional fields, croplands, and roadsides. Four natu- ral wetland communities are present: small, scattered shrub swamps, an extensive marsh, an extensive wet-mesic floodplain forest, and a small, wet floodplain forest. The present study was undertaken to document the vascular flora in these plant communities at the 38 CMNA, and to determine the composition and structure of the extensive wet-mesic floodplain forest. MATERIALS AND METHODS Field trips were made to the CMNA at various times in late 1994, every two weeks dur- ing the growing season of 1995 and in the summer of 1996. During each trip voucher specimens were collected, habitat data for each taxon were determined, and the plant communities were delineated. A few taxa were not collected as they were endangered or rarely encountered at the site. The material collected was identified and deposited in the herbarium of the Illinois Natural History Survey (ILLS), Champaign, Illinois. Criteria for designating native and non-native taxa followed Fernald (1950), Steyermark (1963), Mohlenbrock (1986), and Gleason and Cronquist (1991). During the summer of 1995, a 5 ha section (100 m x 500 m) of the wet-mesic floodplain forest was divided into 80 quadrats 25 m on a side. In each quadrat all living and dead- standing tree individuals 6 cm dbh (diameter at breast height, 1.5 meter above the ground) and above were identified and their diameters recorded. From these data the density (stems/ha), basal area (m2/ha), relative density, relative dominance, importance value (IV), and average diameter (cm) were calculated for each species. The determina- tion of the IV follows the procedure used by McIntosh (1957), and is the sum of the rela- tive density and relative dominance of a given species. The density (stems/ha) of the understory tree species was determined using 80 nested circular plots 0.0001, 0.001, and 0.01 ha in size randomly located along line transects through the study area. Two addi- tional 0.0001 ha circular plots were located 6 m to the east and west of each center. In the 0.0001 ha plots seedlings (<50 cm tall) and all shrubs were counted, in the 0.001 ha circular plots small saplings (>50 cm tall and <2.5 cm dbh) were recorded, and in the 0.01 ha circular plots large saplings (2.5-5.9 cm dbh) were tallied. Nomenclature pri- marily follows Mohlenbrock (1986). DESCRIPTION OF THE STUDY AREA The CMNA is 393 acres (159 ha) in size, and contains the 128 acre (51.8 ha) Chauncey Marsh Nature Preserve (T5N, R12W, S30). Located in northwestern Lawrence County, Illinois, it is in the Bottomland Section of the Wabash Border Division (Schwegman et al. 1973). This section encompasses the bottomland forest, sloughs, marshes, and ox-bow lakes in the floodplain of the Wabash River, the Ohio River, and their major tributaries. The presettlement vegetation of this section was mostly bottomland forest, though wet prairies, marshes, upland forest and shrub swamps were commonly associated with the sloughs and ox-bow lakes. The forest surveyed is located near the middle of a large tract of timber at the CMNA. This wet-mesic floodplain forest (White and Madany 1978) is situated on a terrace of the Embarras River. This terrace is 131 m above sea level, and about 4 m above the normal flow of the river. The forest is flooded for short periods of time in most years; for about eight days during the spring of 1995, and for two months during the spring of 1996. 39 Soils of the CMNA are alluvial deposits from the Embarras River. The soil of the wet- mesic floodplain forest is predominately Darwin clay which occurs extensively on the Embarras and Wabash river floodplain and has developed under very poor natural drain- age (Fehrenbacher and Odell 1956). The soil of the wet floodplain forest, shrub forest, and marsh is Wabash silty clay which occurs in sloughs and old, partially filled channels. The black, plastic silty clay or clay is formed from fine-textured sediments deposited by slack water and from large accumulations of organic matter (Fehrenbacher and Odell 1956). The climate of east-central Illinois is continental with cool winters, hot summers, and little or no water deficit at any season of the year (Page 1949, Fehrenbacher et al. 1967, Schwegman et al. 1973). Average annual precipitation is between 101 and 106 cm, with most occurring in the spring. In Palestine, Illinois, just 15 km to the north, the average precipitation is 104.5 cm, with the month of May having the highest rainfall. Mean aver- age temperature in Palestine, Illinois is 12.7°C with the hottest month being July (average of 25.3°C), and the coldest month being January (average of -0.9°C). The average num- ber of frost free days is between 180-190. RESULTS AND DISCUSSION Vascular Plant Species Present The flora of CMNA consists of 351 species and subspecific taxa within 224 genera and 78 families. Of these taxa, 60 (17%) were not native to Illinois, and several taxa planted in a man-made prairie were probably not original components of this natural area. Only one Illinois endangered species, Silene regia Sims (royal catchfly) was encountered, and no state threatened species were observed (Herkert 1991). The royal catchfly was planted in the man-made prairie. As expected, the fern and fern-allies were poorly represented at the CMNA accounting for only five taxa (1% of all taxa). Gymnosperms were not represented, the Angiosperms accounting for the remaining species. Among the Angiosperms, monocots accounted for 101 taxa (29% of all taxa) in 50 genera and 12 families, while dicots made-up the remainder, 245 taxa (70% of all taxa) in 170 genera and 62 families. The largest genera were Carex with 20 species and Polygonum with 10 species. The largest families were Poaceae (48), Asteraceae (33), Cyperaceae (30), Fabaceae (16), Rosaceae (15), and Poly- gonaceae (14). For a complete list of taxa see Appendix 1. Habitat Types Present Plant communities were designated using the Illinois Natural Areas Inventory (White and Madany 1978). The communities are influenced by periodic flooding of the Embarras River, management practices such as controlled burning and wildlife activities, particu- larly by white-tailed deer (Odocoileus virginianus). Below is a description of each plant community at the CMNA along with the indicator species. 1. Wet-mesic floodplain forests (110.1 ha) occur on poorly drained soils that are periodi- cally flooded during a portion of the growing season and are characterized by a high diversity of deciduous tree species. More than 20 tree species made up the overstory, with Carya laciniosa, Liquidambar styraciflua, Quercus palustris, Acer saccharinum, 40 Ulmus americana, Q. bicolor, and Celtis occidentalis being the most common. Few woody species occur in the very open understory, although the woody vines Campsis radicans, Toxicodendron radicans, and Vitis cinerea are common. The herbaceous layer is dominated by Aster lanceolatus, A . ontarionis, Cryptotaenia canadensis, Geum canadense, Laportea canadensis, Leersia virginica, Pilea pumila, Sicyos angulatus, Solidago gigantea, and Zizia aurea. 2. Wet floodplain forests (9.0 ha) occur in areas frequently flooded during the growing season and are characterized by a low diversity of woody and herbaceous species. Dominant tree species include Acer saccharinum, A. negundo, Populus deltoides, and Fraxinus pennsylvanica.