Litterfall and Leaf Decay in Three Australian Rainforest Formations

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Abstract
(1) Litterfall was measured monthly over five years (1979-84) in three representative rainforest formations of New South Wales, Australia. Known weights of leaf material of selected canopy tree species were laid out on the forest floor in mesh bags and weighed monthly to determine relative rates of lead decay. (2) Mean annual litterfall was 6.2 (.+-.0.22), 7.3 (.+-.0.57), and 10.0 (.+-.0.74) t ha-1 for cool temperate (microphyll fern forest or MFF), warm temperate (simply notophyll vine forest or SNVF), and subtropical (complex notophyll vine forest or CNVF) rainforests, respectively, with an average of 7.4 t ha-1 for rainforests in New South Wales. (3) Litter caught in traps was sorted into major components of leaf material, wood and reproductive parts for two years to determine proportions of each component and to quantify the seasonal patterns of the canopy. Leaf material averaged 54% over all years and sites, with 35% wood and 11% reproductive parts. MFF exhibited bimodal peaks of leaf-fall in autumn (March-June) and spring (September-October), while CNVF canopies showed a summer leaf-fall peak (November-December), and SNVF had an early summer (October-December) leaf-fall peak. (4) Multiple analyses of variance were performed on the data to analyse a range of spatial and temporal factors affecting litterfall measurements. In some cases, estimates of litterfall were significantly affected by presence of overhanging subcanopy branches, closeness to tree trunks, and species of canopy tree overhead. Litterfall did not vary with placement of traps between rainforest patches, under different sides of one tree, at different distances away from the trunk of one tree (albeit under its canopy) or among individuals of the same canopy species. (5) Australian rainforest trees exhibited variability in rates of lead decay, ranging from less than six months for complete leaf decay in Dendrocnide excelsa to over three years for Nothofagus moorei. (6) The differences in litterfall and leaf decay rates are discussed in relation to differences in biomass, seasonality, and activities of canopy-associated fauna of these rainforest formations.