An appraisal of techniques for the study of litter decomposition in eucalypt forests

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Abstract
The merits of methods which have been or could be used to estimate the rate of decomposition of litter in eucalypt forests are discussed, and recommendations are given for their improved application. Since each method has serious limitations, several approaches need to be combined in most studies for conclusions to be drawn with confidence.Suitable methods for studying the loss of weight of litter as it decays include the use of mesh bags, the tethering of leaves, the measurement of respiration rate, and the temporal comparison of inputs of litter with changes in accumulated litter. Where the litter can be aged with some confidence (e.g. after afire) and where grazing by litter invertebrates is low, the loss of weight per unit of leaf area is a useful index of the decomposition rate of leaves in situ. For study of the pattern of nutrient release from litter the most promising method is the collection and analysis of litter leachate. Fresh, naturally shed litter should usually be used in studies which require measurements on a selected sample. Green foliage picked from branches normally has a much higher nutrient content and decomposes more rapidly than leaves which are naturally abscissed.Difficulty in identifying and thus measuring the weight of the incorporated component (mull‐type humus) of accumulated litter, and the likely absence of steady‐state quantities of accumulated litter because of widespread fires, seriously hinder both the estimation and application of decomposition constants (k) in Australian eucalypt forests.Based on limited available evidence, initial rates of litter decomposition (e.g. as measured in litterbags over a 12–18 month period) should not be extrapolated to predict long‐term rates of decomposition.In several eucalypt forests, the major release of organically bound nutrients does not occur until litter has undergone several years of decay, and probably occurs after some fragmentation and incorporation of litter into the surface soil. Much more information is needed on these processes, including the role of C: element ratio, litter fauna, changed microclimate as litter is incorporated, and the influence of plant roots on mineralization processes.