Woody Vegetation and Microtopography in the Bog Meadow Association of Cedar Bog, a West-central Ohio Fen

Abstract

The bog meadow association, a fen at Cedar Bog Nature Preserve in W-central Ohio, was studied to determine the short range establishment potential of woody species, especially arbor vitae (Thuja occidentalis). The presence of numerous arbor vitae seedlings and saplings, a 54% winter survival rate of seedlings, and possible invasion of the meadow by peripheral arbor vitae via branch-layering suggest that this tree species is invading the bog meadow. This vegetation change is thought to be recent and indicates succession of the bog meadow toward an arbor vitae forest. Active management of the vegetation in the preserve is recommended to maintain the bog meadow association as an herb-dominated fen. INTRODUCTION Cedar Bog Nature Preserve, Champaign Co., Ohio, contains a 20-ha relict of what was formerly a 2800-ha complex of wetlands and forest in W-central Ohio. Many of the plant species in the preserve occur S of their normal range, and Braun (1950) considered Cedar Bog to be the most southerly of the well-preserved bog remnants in North America. It is the only remaining alkaline fen in Ohio (Forsyth, 1974). As such, the area is an important relict of the rapidly disappearing northern wetlands. Frederick (1974) identified six plant associations in the preserve: bog meadow, marl meadow, arbor vitae, swamp forest, shrub and hardwood forest. The most ubiquitous tree species is arbor vitae (Thuja occidentalis') which is present in all associations except the hardwood forest. Frederick (1974) found small arbor vitae trees growing on many of the larger hummocks near the margins of the bog meadow. Braun (1928) hypothesized that portions of Cedar Bog were undergoing succession from bog meadow through an arbor vitae stage, and eventually developing into hardwood forest. If this is true, arbor vitae should be successfully invading treeless associations such as the bog meadow. The soil of the bog meadow association is an alkaline, wet marl resulting from groundwater which surfaces after passing through dolomitic glacial deposits (Forsyth, 1974). Therefore, this association is correctly classified as a fen, a type of vegetation which has been considered a precursor to bog and swamp forest communities (Moore and Bellamy, 1974). The meadow contains closely spaced hummocks of low elevation (< 0.5 m high) and 0.5-1.5 m in diam, which produce microenvironmental gradients from wet marl between hummocks to Carex-Sphagnum covered hummock tops. Invasion and establishment of woody species may be related to the microenvironmental gradients associated with these hummocks. The purposes of our study were to: (1) describe the woody vegetation in the bog meadow association; (2) evaluate the potential increase of woody species, especially arbor vitae, in the meadow, and (3) relate distribution of woody species to microtopographic position. MATERIALS AND METHODS Six belt transects 2 m wide and varying in length from 7.5-45 m were located 1 Department of Botany and Microbiology, University of Oklahoma, Norman 73019. 2 Perino & Associates, 900 West Lake Drive, Springfield, Illinois 62707. 1 Nomenclature follows Weishaupt (1971).