Decline in tree-fern abundance after clearfell harvesting

Abstract

Common and widespread plant species can change in abundance as a result of timber harvesting practices, with potentially broad effects on an ecosystem. Yet few studies have quantified such changes and their effects and as a result, subsequent management can be poorly defined. Tree-ferns are among a number of vegetative resprouters that have been shown to decline in abundance after clearfelling in Victorian Wet Forest. This study quantifies the initial survival of two common species of tree fern, Dicksonia antarctica and Cyathea australis, on six Wet Forest coupes in the Victorian Central Highlands, south-eastern Australia. Sixteen percent of the 2391 tree-ferns monitored remained alive 1 year after clearfelling and seedbed preparation, with only 5% remaining in an upright position. Mortality was still increasing up to 6 years after clearfell harvesting, particularly for C. australis. Sixty-seven percent of D. antarctica surviving to 1 year post-harvest were still alive after 4 or 6 years, whereas only 35% of C. australis survived this period. Low tree-fern survival is likely to result in declines in the abundance of other species that rely directly on tree-ferns for habitat. The altered forest structure resulting from reduced tree-fern numbers will affect local microclimates and forest processes. As tree-fern recruitment is low and growth rates are slow, these changes are likely to be long term. Survival of individuals through harvesting operations is crucial to the maintenance of the role of tree-ferns as a keystone species in Wet Forests and simple modifications to current practices could increase the survival of tree-ferns in clearfelled areas.