Palaeoecology and Development of Peatlands in Indiana

Abstract

The progressive development of ten Holocene peatlands in northeast Indiana was determined by analysis of macroscopic subfossils recovered from sediment cores. All of the peatlands began as extremely mineral-rich lakes or ponds after retreat of Wisconsin-age glacial ice. The oldest basal date was 13,170 radiocarbon 14C y BP. The subfossil assemblage characterizing the lake stages included Chara sp., Ceratophyllum demersum, Najas flexilis and Potamogeton spp. The transition from lake to peatland was marked by a marsh flora dominated by Nuphar sp. Nymphaea sp., and, especially, Brasenia schreberi. Evidence for the development of a fen began early in the hydrosere (in the limnic phase) and colonization of the open water by a floating fen mat brought closure to the emergent marsh. Calcicolous mosses of the family Amblystegiaceae, including Calliergon stramineum, Calliergon trifarium, Campylium polygamum, Drepanocladus aduncus and Scorpidium scorpioides, dominated the fens. During the later stages of the fen phase an association of Calliergon trifarium and Meesia triquetra dominated the subfossil assemblage. Depending on the morphometry and geology of the respective basins, some of the fens became Sphagnum-dominated bogs. Subfossil assemblages of the bog phase included remains of ericaceous shrubs as well as sedges. Regardless of their developmental pathways, all of the peatlands exhibit an apparent trend towards senescence into lowland forests dominated by Acer rubrum.