Palaeoecology and development of peatlands in Indiana

The progressive development of ten Holocene peatlands in northeast Indiana was determined by analysis of macroscopic subfossils recovered from sedimen t cores. All of the peatlands began as extremely mineral-rich lakes or pond s after retreat of Wisconsin-age: glacial ice. The oldest basal date was 13 ,170 radiocarbon C-14 y BP. The subfossil assemblage characterizing the lak e stages included Chara sp., Ceratophyllum demersum, Najas flexilis anti Po tamogeton spp. The transition from lake to peatland was marked by a marsh f lora dominated by Nuhar sp. Nymphaea sp., and, especially, Brasenia schrebe ri. 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 Amb lystegiaceae, including Calliergon stramineum, Calliergon trifarium, Campyl ium polygamum, Drepanocladus aduncus and Scorpidium scorpioides, dominated the fens. During the later stages of the fen phase an association of Callie rgon trifarium and Meesia triquetra dominated the subfossil assemblage. Dep ending on the morphometry and geology of the respective basins, some of the fens became Sphragnum-dominated bogs. Subfossil assemblages of the bog pha se included remains of ericaceous shrubs as well as sedges. Regardless of t heir developmental pathways, all of the peatlands exhibit an apparent trend towards senescence into lowland forests dominated by Acer rubrum.