A comparison of oldgrowth mixed forest with regeneration resulting from logging or wildfire

Up to 194,000 ha, or 20 percent, of Tasmania's wet eucalypt forest is mature mixed forest greater than 110 years old. At least 33 percent of the mixed forest is reserved in the Tasmanian Wilderness World Heritage Area (TVVWHA) or in State and Forest Reserves outside the TWWHA. Almost half the area of mixed forest with a mature myrtle understorey has a eucalypt density of only 5-20 percent which implies that it is in the last successional stage prior to becoming rainforest. A comparison of the floristics of 20-30-year-old silvicultural and wildfire regeneration with oldgrowth mixed forest showed that species richness for all lifeforms other than epiphytic ferns was greater in regenerated forest than in oldgrowth mixed forest. Most of the common species in oldgrowth mixed forest were represented in approximately similar frequencies in silvicultural and wildfire regeneration. The major floristic difference between the two regeneration types was the much lower frequency of epiphytic fern species in silvicultural regeneration. The floristic composition of oldgrowth mixed forest is profoundly influenced by either wildfire or clearfelling and slash burning but the composition of the regeneration is more influenced by environmental variables than by the nature of the disturbance which initiated the regeneration. Comparisons indicated only slight differences in growth and density of tree and tall shrub species between silvicultural and wildfire regeneration. Growth of rainforest tree species in young regenerated stands was very slow due, apparently, to suppression by a dense layer of taller sclerophyllous trees and shrubs. The density of most rainforest tree species was lower in regenerated sites than in oldgrowth mixed forest but there was no significant difference between logged and wildfire sites. The density of common rainforest shrub species was similar in all three site types. Several rainforest species with short seed dispersal distances can regenerate vegetatively after fire. There was no difference between silvicultural and wildfire regeneration in the amount of vegetative regeneration of rainforest canopy species. Basal sprouting of rainforest canopy species occurred in the first year following disturbance but seedlings took several years to become established. No significant differences were found in seedling establishment time of rainforest canopy species. Five woody rainforest species regenerated from soil seed banks and included two species which took more than one year to germinate. The species similarity between oldgrowth mixed forest stands and their soil seed banks was low.