A comparison between regeneration patterns of Eucalyptus regnans and mixed forest species, on logged coupes in South West Tasmania

The effect of different stages of forestry practices on regeneration of Eucalyptus regnans and understorey and rainforest species was determined for logged coupes in South West Tasmania. Observations were made across six different logged sites which were mixed forests prior to logging. Results at different stages of logging activity were investigated with undisturbed mixed forests used as controls. Mudstone is the main rock type at the study sites, and on some sites was found to be combined with quartzite. Study sites were divided into two groups. The first group, unburnt sites, consisted of unlogged mixed forest sites, sites from which eucalypts had been selectively logged, and clearfelled sites. The second group consisted of sites which had been burnt. Sample quadrats on the burnt sites were classified according to fire intensity; unburnt (small patches within the generally burnt area), low medium and high fire intensities. Sites were classified as two, five, seven and nine years after burning. Regeneration of rainforest species occurred on logged sites, with regeneration on unburnt sites and on unburnt quadrats of burnt sites significantly greater than the regeneration of Eucalyptus regnans. Stocking rates of rainforest species was found to decrease with increasing fire intensity. A positive association occurs between the density of rainforest seedlings and mosses, and a negative association between density of rainforest seedlings and shrubs and ferns. Nothofagus cunninghamii and Eucryphia lucida regenerate better than other rainforest species. No significant difference was found between the regeneration rates of Nothofagus cunninghamii and Eucryphia lucida. Evidence was found which indicates that floristic composition changes with increasing time since fire and with different fire intensities. Eucalyptus regnans was found to regenerate poorly. On burnt sites, stocking rates of E. regnans increased with increasing fire intensity and this increase varied according to both fire intensity and time since fire. However, no strong evidence was found which indicated that greater stocking rates existed in quadrats on unburnt or burnt parts of the burnt sites. In contrast, when results were expressed in terms of mean seedling number, there was found to be a significant difference in the regeneration of Eucalyptus regnans in quadrats where fire had occurred compared to quadrats in unburnt parts of burnt sites with increasing time since fire. Furthermore, fire intensity did not affect regeneration rates and there was no obvious interaction between fire intensity and the time since fire. All species investigated were found to regenerate poorly on quartzite. Eucalyptus regnans stocking rates were not affected by fire intensity on quartzite sites. Phebalium squameum tended to be the most frequent tree seedling associated with Eucalyptus regnans on logged sites following fire. Acacia species were uncommon on the study sites. Photosynthetic responses to light and frost resistance of the main species were measured, in order to correlate field observations with the physiology of selected species. Based on photosynthetic responses to light, P hebalium squameum and Eucalyptus regnans are considered to be relatively light requiring (sun plants). The ferns Pteridium esculentum, Histiopteris incisa, Hypolepis muelleri and the hepatic Marchantia berteroana, dominate the ground layer of burnt sites during the early stages of recolonisation. The dominant shrubs on all sites, burnt and unburnt, included Anopterus glandulosus and Monotoca glauca. Mosses dominate the ground layer on all sites, at all the intervals since fire that were examined. The greatest number of species were found in sites where five years had elapsed since burning. Compared to undisturbed forest sites, sites two years after fire have a low index of similarity (approximately 50%). All other sites have indices of similarity which exceed 50%.