The fungal communities of decomposing plants in southern boreal peatlands of Alberta, Canada

Peatlands are some of the world's most important ecosystems, primarily because they cover a large area of the world and store large quantities of carbon in peat. Under a global warming scenario, this peat is predicted to decompose more rapidly than at current rates, thereby releasing increasing quantities of CO2 and/or CH4 into the atmosphere, providing a positive feedback to global warming. Therefore, it is important to understand current decomposition dynamics of plant litters in peatlands and gain an understanding of the microbial communities involved in the decomposition of these materials.;In a decomposition study of above- and belowground plant litters in a fen and a bog in southern boreal Alberta, mass losses of Carex aquatilis rhizomes significantly exceeded those of C. aquatilis leaves, Salix planifolia leaves, S. planifolia roots, and Sphagnum fuscum after two years. Tissue nutrient concentrations and alkalinity- and phosphorus-related surface water chemistry variables explained most of the variation observed in these mass losses. Over 90 different fungal species were isolated from these plant litters. Community analyses showed that significantly different fungal communities (mycotas) were involved in the decomposition of these litters, with clear separations among the mycotas of the root, rhizome, and bryophyte litters. The mycotas of the leaf litters were similar to each other. Furthermore, distinct successional patterns of the mycota were apparent in the S. fuscum and C. aquatilis leaf and rhizome litters. Contrary to the literature, litter quality variables accounted for most of the underlying trends, with environmental variables playing only a minor role.;A comparative in vitro analysis of fungal and bacterial decomposition of Sphagnum fuscum and Carex aquatilis leaves and rhizomes at two temperatures showed that fungi caused greater mass losses at elevated temperatures (6°C temperature increase), similar to those predicted under a global warming scenario. Mass losses of S. fuscum by bacteria were significantly greater than those by fungi at current mean growing season temperatures. These data suggest that increased decomposition rates of peat in peatlands as predicted by current ecosystem climate models may be premature and simplistic.;Nutrients released into the soil and water columns during the process of decomposition are then available for plant uptake. Mycorrhizal fungi associated with roots of most bog and fen plant species (Ericaceae, Pinaceae, Salicaceae) facilitate the acquisition of these nutrients and ensure plant vigor and survival. In contrast, plants belonging to the Cyperaceae and Typhaceae in fens and marshes were non-mycorrhizal, but had a suite of often dark-coloured, septate fungi associated with their roots. These may act like mycorrhizal fungi in some instances, aiding plants in the acquisition of nutrients.