Studies of Litter in Eucalyptus regnans Forests

Abstract

The litter of Eucalyptus regnans forests forms a mull humus, and leaf material is readily incorporated into the topsoil. The annual litter fall is high by world standards, averaging 7.66 tonneslha. The amount of bark and twig fall and the contribution of the understorey to the total litter are also com- paratively high. The annual leaf fall in even-aged stands is in the order of spar stage > mature > pole stage. The maximum fall at 40-50 years coincides with the culmination of annual growth increment. Leaf fall is at a maximum in summer and early autumn and at a minimum in winter and early spring. The nutrient return by the total litter is fairly high, although bark and wood have low nutrient contents. The understorey of Pomaderris aspera contributes much of the calcium return. Leaf litter decays and disintegrates within 12-18 months, but bark and wood tends to accumulate on the floor. Crustaceans, millipedes and earthworms contribute to the incorporation of leaf material. Their number fluctuates seasonally, locally and between stands. Lyrebirds are important 'cultivators' of the forest floor and litter may be buried once every two years. Rapid nutrient turnover, high rainfall and excellent soil structure are favourable for high growth rates of these forests.