Early impacts of disturbance on lichens, mosses and liverworts in Tasmania’s wet eucalypt production forests

The impacts of silvicultural disturbance (felling and burning) on lichens, mosses and liverworts in Eucalyptus obliqua-dominated wet forest in Tasmania were investigated. The study was based on presence–absence data for 452 taxa from 52 sampling events, spanning unlogged forest and disturbed, regenerating forest about 1, 3 and 5 years after disturbance. Three aspects of species composition were compared: total species richness, occurrence of pre-disturbance species in the post-disturbance flora and relative richness of ecological groups in the flora. Total species richness was the least reliable measure for evaluating changes due to disturbance.

Felling and burning in different combinations were represented in a range of silvicultural treatments applied in the study area. They produced different levels of disturbance and different microhabitats, and thereby defined the character of the cryptogamic flora. The most severe impacts occurred at burnt sites, regardless of whether the forest had been felled or not, and the least impact was found in standing, unburnt forest.

The consequences of severe disturbance were a substantial change in species composition, with a reduction, in particular, of mature wet forest species in favour of species associated with disturbance or brightly lit, exposed environments. In the lichens, the loss of old tree indicators, old forest indicators, foliicolous species, rare species of conservation significance and species indicative of a succession towards cool temperate rainforest was especially severe. Mosses and liverworts also showed a very pronounced loss of mature wet forest species. In the mosses, the presence of newcomers, represented mostly by disturbance species or species typical of open drier conditions, masked the extent of these losses. In the liverworts, there were few newcomers and the composition of the post-disturbance flora was much depleted.