The Dynamics of Some Rainforest Associations in Tasmania

Publisher Website
Google Scholar
Abstract
(1) Spatial and temporal patterns of regeneration of the major Tasmanian cool temperate rainforest canopy species were investigated. Nothofagus cunninghamii, Eucryphia lucida and Atherosperma moschatum generally exhibit continuous regeneration and tend towards self-replacement. Evidence of autogenic replacement of N. cunninghamii and E. lucida by the more shade-tolerant A. moschatum, as predicted by successional theories, was not observed, but would take many generations due to the slow dispersal rate of A. moschatum through rainforest. (2) The endemic conifers, Phyllocladus asplenifolius and Athrotoxis selaginoides regenerate continuously in open vegetation, and occassionally in large canopy gaps created by natural tree death in closed forest, where competition with co-occurring species is low. However, both species particularly P. asplenifolius which is most frequent in scrub rainforests on poor soils in which canopy gaps are small and quickly occupied by species which reproduced vegetatively, commonly occur in a narrow range of size classes. This size structure is indicative of regeneration following a large scale disturbance and inability of the species to regenerate in the mature closed forest. (3) Canopy composition and dynamics in Tasmanian rainforest is, therefore, influenced by differences among species in the modes of reproduction, and in tolerance of the light environment under the canopy. However, autogenic replacement of canopy species by those with greater shade-tolerance is infrequent because of the slow rate of replacement relative to the frequency of catastrophic disturbance.