THE EFFECTS OF FORAGING BY THE SUPERB LYREBIRD (MENURA-NOVAE-HOLLANDIAE) IN EUCALYPTUS-REGNANS FORESTS AT BEENAK, VICTORIA

In an early spar-stage stand of Eucalyptus regnans at Beenak, Victoria , foraging by lyrebirds in bare floor areas on steep slopes results in a complex microtopography of excavations, accumulations and terracett es. About 200 t ha(-1) of litter and top soil may be displaced an aver age of 70 cm downhill per year. Magnetic ferruginous pisolite was used as a marker to monitor progressive soil movement over 3 years. Very l ittle disturbance occurred in areas of dense ground fern, but in bare areas the whole forest floor may be turned over every 20 months. In th e site studied, foraging activity by lyrebirds varied seasonally and t opographically. Disturbance by other biotic agents was minimal. The me an depth of soil cultivation was about 10 cm and litter was frequently buried or mixed intimately with soil. Since buried leaf litter decays more quickly than that on the surface, lyrebird foraging is likely to increase the rate of nutrient cycling. The small, steep clifflets lef t at the uphill limits of each scratch microsite provide litter-free n iches for the establishment of tree fern prothalli and shade-tolerant herbs. All stages in the growth of the rough tree fern, Cyathea austra lis, were present in bare floor areas, but in dense ground fern patche s, young stages were confined to rotten logs and upturned root balls. Since dense tree fern development tends to diminish the cover of dense ground fern, lyrebird foraging activity may maintain an accessible fo od resource which would otherwise diminish with increased ground fern cover in these forests in the course of secondary succession after fir e.