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C-NMR analysis of decomposing litter and fine roots in the semi-arid Mulga Lands of southern Queensland |
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| Authors: | Nicole J Mathers Rajesh K Jalota Ram C Dalal Sue E Boyd |
| Institution: | a CRC for Greenhouse Accounting, GPO Box 475, Canberra, ACT 2601, Australia b Queensland Department of Natural Resources and Water, 80 Meiers Road, Indooroopilly, Qld. 4068, Australia c PIRVic, DPI Ellinbank, 1301 Hazeldean Road, Ellinbank, Vic. 3821, Australia d Centre for Forestry and Horticultural Research, Griffith University, Kessels Road, Nathan, Qld. 4111, Australia |
| Abstract: | Plant litter and fine roots are important carbon (C) inputs to soil and a direct source of CO2 to the atmosphere. Solid-state carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy was used to investigate the nature of C changes during decomposition of plant litter and fine roots of mulga (Acacia aneura F. Muell. Ex. Benth.), wheat (Triticum aestivum L.), lucerne (Medicago sativa) and buffel grass (Cenchrus ciliaris) over an 18-month period. Alkyl C was closely associated with total N concentrations in all litter materials during decay and as alkyl C increased so did total N, indicating an increase in refractory biomacromolecules. Mulga phyllodes had the greatest alkyl C concentration of all litter and fine root materials, and also exhibited the NMR peaks assigned to tannins that may slow or hinder decomposition rates and nitrification. Mulga litter and fine roots decomposed slower than all other litter materials and the soil under mulga had the highest soil C concentration, indicating slower CO2 release. The alkyl C-to-O-alkyl C ratio is generally used as an index of the extent of decomposition, but is not useful for the decay of woody components. Of all the NMR ratios studied that may indicate the extent of decomposition, the carbohydrate C-to-methoxyl C ratio proved to have the strongest and most consistent relationship with decay time, fraction of mass remaining and total C, even though increases in alkyl C were observed with decreases in carbohydrate C. |
| Keywords: | Litter decomposition Fine roots 13C-NMR spectroscopy Mulga Buffel grass Semi-arid C sequestration Land-use change |
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