Ecological studies of Acmena smithii (Poir.) Merrill & Perry with special reference to Wilson's Promontory

Abstract

The Acmena smithii species complex occurs in a wide range of rain-forests (closed-forests) from 11� to 39� S. in eastern Australia. At its southernmost limit on Wilson's Promontory, it forms a structurally and floristically simple closed-forest of the microphyll fern type, and usually occurs up to altitudes of 300 m on relatively fertile alluvial and colluvial soils. It is replaced by thickets of Melaleuca spp. on very waterlogged soils and by nanophyll mossy forests of Nothofagus cunninghamii and Atherosperma moschatum at higher altitudes. It is often associated with emergent fire-induced strata of Acacia melanoxylon and Eucalyptus obliqua. On Wilson's Promontory, A. smithii rain-forest is a climax in fire-sheltered lowland gullies. In the prolonged absence of fire many adjacent wet sclerophyll (tall-open) forests are replaced by such rain-forest. A. smithii is extremely shade-tolerant and regenerates readily under dense forest canopy and in gaps. The seed is easily killed by desiccation and is frequently decimated by birds and insects. Slow development of seedlings in the first year renders them susceptible to drought and browsing. After the second year they are extremely persistent owing to the development of a lignotuber. The litter fall is heavy and decays rapidly to form a mull humus on relatively fertile loams and poor podzolic soils. The shoots of A. smithii grow during the frost-prone seasons of the year. This characteristic is correlated with its restriction to low altitudes in a mild maritime environment. The problems of the dispersal and past distribution of A. smithii are briefly discussed.