Microbial communities in natural and disturbed peatlands: A review

Even though large extents of boreal peatlands are still in a pristine condition, especially in North America, extensive areas have been affected by natural or anthropogenic disturbances that change some of the systems from being sinks to sources of carbon dioxide and shift the methane production/consumption patterns through alterations of both above- and below-ground communities and functions. In order to fully assess the role of peatlands on global C balance, now and in the future, it is imperative that we deepen our understanding of the relative contributions of various groups of microorganisms to organic matter transformations. Here, we review the drivers structuring fungal, bacterial and archaeal communities in natural peatlands and the response of these microbial communities to natural and anthropogenic disturbances, including fire, drainage, nutrient deposition, peat mining and climate change. The microbial diversity in peatlands is characterized by organisms that have developed physiological and metabolic adaptations to cope with the constraining conditions found in these ecosystems, such as low oxygen availability, cold temperature, acidity and oligotrophy. Furthermore, these unique organisms sometimes appear to be organized as repeat mosaics responding to vegetation, physicochemical and hydrological characteristics more than to geographical distance, in other words, similar to the much valued biodiversity aspects of the peatland vegetation itself and associated higher organisms. The response of microbial communities to disturbances is far from fully understood. In particular, whilst many studies have identified changes in microbial community composition or on microbially driven processes following a given disturbance, it remains unclear how the two components, diversity and function, relate with each other. Future challenges involve designing studies that will test whether ecological theories like species sorting, stress physiology, temporal niche or functional redundancy can be used to understand what regulates microbial populations and activity in peatlands, and studies that will allow us to predict more accurately how peatlands respond to global change or anthropogenic disturbances. (C) 2012 Elsevier Ltd. All rights reserved.