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The fate of 15N-nitrate in a northern peatland impacted by long term experimental nitrogen, phosphorus and potassium fertilization |
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| Authors: | Yangping Xing Jill Bubier Tim Moore Meaghan Murphy Nathan Basiliko Sybille Wendel Christian Blodau |
| Affiliation: | 1. Limnological Research Station and Department of Hydrology, University of Bayreuth, 95440, Bayreuth, Germany 6. Department of Earth Science, University of Ottawa, 140 Louis Pasteur Street, Ottawa, ON, K1N 6N5, Canada 2. Environmental Studies Program, Mount Holyoke College, 50 College Street, South Hadley, MA, 01075, USA 3. Department of Geography and the Global Environmental and Climate Change Centre, McGill University, 805 Sherbrooke Street W, Montreal, QC, H3A2K6, Canada 4. Department of Geography, University of Toronto at Mississauga, 3359 Mississauga Road North, Mississauga, ON, L5L1C6, Canada 5. School of Environmental Sciences, University of Guelph, Guelph, ON, Canada |
| Abstract: | Information about the impact of nitrogen (N) deposition on the fate of deposited N in peatland ecosystems is lacking. Thus we investigated the fate of experimentally added 15N in long-term N-fertilized treatments in a Sphagnum-dominated ombrotrophic bog. Fertilization significantly stimulated vascular plant and suppressed Sphagnum and Polytrichum moss growth. N content in peat, mosses, and vascular plants was raised by the fertilizer addition and reached a maximum at 3.2 g m?2 N input level with phosphorus (P) and potassium (K) addition. Most of N was retained in the vegetation and upper 10 cm of the peat. When N deposition equalled 1.6 g m?2 and less, or 3.2 g m?2 N with P and K addition, no inorganic N leaching was observed on the plots. This result indicates that co-fertilization with P and K raised the N retention capacity and that critical N loads with respect to N saturation depend on P and K availability. Most of the deposited 15N was recovered in the bulk peat, which may be related to a rapid immobilization of inorganic N by microorganisms and mycorrhizal assimilation. Increase of N, P, and K fertilization increased the contribution of vascular plants to N retention significantly and reduced those of mosses. The increase was mainly related to enhanced productivity, vascular biomass and N content in tissues; the reduced retention by mosses resulted from both reduced moss biomass and assimilation. The study shows that the N filter function of ombrotrophic bogs will be influenced by interactions with other nutrients and shifts in plant community structure. |
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