Immobilization of 15N in forest litter studied by 15N CPMAS NMR spectroscopy |
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| Authors: | PW CLINTON RH NEWMAN RB ALLEN |
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| Institution: | New Zealand Forest Research Institute Ltd, c/-University of Canterbury, Private Bag 4800, Christchurch, New Zealand;Industrial Research Ltd, PO Box 31-310, Lower Hutt, New Zealand;Landcare Research New Zealand Ltd, PO Box 69, Lincoln, New Zealand |
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| Abstract: | Solutions labelled with 15N were applied as (15NH4)2SO4 or K15NO3 to isolated microplots in the floor of mountain beech forest (Nothofagus solandri var. cliffortioides) and incubated for 135 days under field conditions of moisture and temperature. Solid state 15N CPMAS NMR spectra of the forest litter layer showed that more than 80% of the total signal intensity was attributable to the secondary amide-peptide peak. The degree of 15N enrichment or form of N did not alter the relative intensity of signals attributable to 15N in peptides, nucleic acids and aliphatic amine groups (amino sugars and free NH2 on amino acids). Combinations of 13C and 15N-NMR spectra, edited by a process that exploited differences in proton spin properties between distinct categories of organic matter, indicated incorporation of 15N in humified organic matter rather than partly degraded plant material. This application demonstrated that solid state 15N CPMAS NMR has potential for use in studies of N immobilization under field conditions and with materials containing little N and small 15N enrichment. |
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