%0 Journal Article
%T Nitrogen Release in Pristine and Drained Peat Profiles in Response to Water Table Fluctuations: A Mesocosm Experiment
%A Merjo P. P. Laine
%A Rauni Str£¿mmer
%A Lauri Arvola
%J Applied and Environmental Soil Science
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/694368
%X In the northern hemisphere, variability in hydrological conditions was suggested to increase as a consequence of climate warming, which may result in longer droughts than the area has experienced before. Due to their predominately anoxic conditions, peatlands are expected to respond to changes in hydrological conditions, such as successive drying and rewetting periods. As peatlands are rich in organic matter, any major changes in water table may influence the decomposition of it. The hydrological conditions may also influence release of nutrients from peat profiles as well as affect their transport to downstream ecosystems. In our mesocosm experiment, artificial water table fluctuations in pristine peat profiles caused an increase in dissolved organic nitrogen (DON) and ammonium concentrations, while no response was found in drained peat profiles, although originating from the same peatland complex. 1. Introduction High latitudes are expected to experience considerable climatic warming during the 21st century [1]. As a response to climatic change, the position of the water table in boreal and subarctic peatlands will be modified [2], and heavy precipitation events and number of wet days are expected to increase in northern Europe [3]. Climate change predictions for northern Europe, and specifically for Finland, indicate an increase in precipitation by 5¨C40% and in air temperature by 2¨C7 degrees Celsius (¡ãC) by the 2080s, depending on the climate model and scenario used [4]. Variation in hydrological processes in both space and time causes changes in nutrient transport from land to surface waters [5]. Modelling studies predict that plausible high climate change scenarios will increase the annual N fluxes in small, forested watersheds in Finland. Increase in 30 years in dissolved inorganic nitrogen can be as high as 25% [6]. Holmberg et al. [7] predicted that an increase in total nitrogen load in 40 years can be 26%. Studies concerning the effects of fluctuating water table on N compounds and their concentrations in soil water in peatlands are scarce. Even though anaerobic bacteria are involved in the nitrogen cycle in various ecosystems [8], N mineralization in peatlands is usually more effective in aerobic than in anaerobic conditions and not least in bogs [9]. Therefore, rewetting after a dry period brings an interesting aspect for understanding nutrient dynamics in a changing climate. Also at high latitudes, where annual rainfall is predicted to increase, there may be heavy rainfall events which follow exceptionally dry seasons. For example, in
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