Seasonal variation in carbon isotopic composition of bog plant litter during 3 years of field decomposition

In this study, we describe the seasonal variation in C-13 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 delta C-13 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 delta C-13 probably due to the incorporation of microbial organic compounds rich in C-13 in the residual litter. In the litter of Eriophorum vaginatum, Carex rostrata and Calluna vulgaris, we observed a decrease of delta C-13 with an increase in the concentration of lignin-like compounds. The residual litter of Potentilla erecta showed a decrease of C-13 abundance during the first 2 years, but on proceeding the decomposition, the delta C-13 increased again probably reflecting the incorporation of microbial organic compounds.