Seasonal variation in nitrogen isotopic composition of bog plant litter during 3 years of field decomposition
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In this study, we describe the seasonal variation in 15N abundance in the litter of two Sphagnum species and four vascular plant species during 3 years of field decomposition in an Italian Alpine bog. Litter bags were periodically retrieved at the end of summer and winter periods, and the δ15N in residual litter was related to mass loss, litter chemistry, and climatic conditions. In Sphagnum litter, higher rates of decomposition during summer months were associated with an increase of δ15N probably due to the incorporation of microbial organic compounds rich in 15N. The litter of Eriophorum vaginatum and Carex rostrata was characterized by a decrease of δ15N, so that the final signature was significantly lower than in initial litter. On the other hand, the residual litter of Potentilla erecta and Calluna vulgaris was characterized by a final δ15N higher than in initial litter. Our data reported a seasonality of 15N abundance in the residual litter of Sphagnum species, but not in that of vascular plant species, thus highlighting the role of differences in litter chemistry.
Keywordsδ15N Decomposition Italian Alps Litter C/N quotient Peatland Sphagnum Vascular plants
Thanks are due to I. Targa for field assistance and to R. Marchesini and F. Tressino for laboratory assistance. R. Gerdol acknowledges the funding of this study by the “Fondazione Cassa di Risparmio di Verona, Vicenza, Belluno e Ancona” through the project “R.I.T.A.”, whereas L. Bragazza acknowledges the contribution by the useful discussions during the NSF-RCN (U.S.)-sponsored PEATNET Workshop “Why is There Peat?” (Villanova University, March 27–28, 2008). Helpful comments and suggestions from P. Nannipieri and three anonymous reviewers are also acknowledged.
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