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The importance of bogs in the catchment hydrology of the Australian Alps has been long recognised but little studied. Damaged bogs are thought to be the source of dried peats now common throughout the Alps. We described the characteristics of a bog peat and a dried peat, to better understand the relationship between the two. Standard chemical properties of peat were measured: pH, loss on ignition, gravimetric contents of carbon and nitrogen, and electrical conductivity. We also measured the concentrations of total and plant-available elements, and the chemical composition of the organic carbon, leading to a measure of the extent of decomposition. The results suggest that this is a typical Sphagnum bog peat?low pH, high carbon content?and the distribution of carbon groups and other elements reflect the stable water source of this groundwater-fed Sphagnum bog. The properties of the dried peat were most similar to the catotelm (lower layer) of the bog peat. This resemblance, combined with decades of field observations, indicates that dried peat may form from the catotelm of bog peat, after the acrotelm (upper layer) dries and erodes. These results have implications for the management of Alps catchments, and further studies are needed to ascertain the hydrologic and carbon cycling roles of organic soils in the Australian Alps.

Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy has become an important tool for examining the chemical structure of natural organic materials and the chemical changes associated with decomposition. In this paper, solid-state 13C NMR data pertaining to changes in the chemical composition of a diverse range of natural organic materials, including wood, peat, composts, forest litter layers, and organic materials in surface layers of mineral soils, were reviewed with the objective of deriving an index of the extent of decomposition of such organic materials based on changes in chemical composition. Chemical changes associated with the decomposition of wood varied considerably and were dependent on a strong interaction between the species of wood examined and the species composition of the microbial decomposer community, making the derivation of a single general index applicable to wood decomposition unlikely. For the remaining forms of natural organic residues, decomposition was almost always associated with an increased content of alkyl C and a decreased content of O-alkyl C. The concomitant increase and decrease in alkyl and O-alkyl C contents, respectively, suggested that the ratio of alkyl to O-alkyl carbon (A/O-A ratio) may provide a sensitive index of the extent of decomposition. Contrary to the traditional view that humic substances with an aromatic core accumulate as decomposition proceeds, changes in the aromatic region were variable and suggested a relationship with the activity of lignin-degrading fungi. The A/O-A ratio did appear to provide a sensitive index of extent of decomposition provided that its use was restricted to situations where the organic materials were derived from a common starting material. In addition, the potential for adsorption of highly decomposable materials on mineral soil surfaces and the impacts which such an adsorption may have on bioavailability required consideration when the A/O-A ratio was used to assess the extent of decomposition of organic materials found in mineral soils. Additional keywords: composts, forest litter, peat, soil organic matter, wood, chemical composition.