Longer-term response to experimental manipulation of fallen timber on forest floors of floodplain forest in south-eastern Australia

Abstract

There often are substantial accumulations of fallen timber (logs, large boughs) in many woodlands and forests around the world. However, fallen timber has become a target for removal for use as fuel or for management actions, such as fuel-reduction burning. Many silvicultural practices, such as fast harvesting rotations, coppicing and debris burning prior to re-sowing/re-planting, lead to much reduced fallen-timber loads. Many studies show the ecologically important role fallen timber plays, so its removal is likely to have adverse ecological outcomes. It has previously been shown that a specialized forager on fallen timber, the brown treecreeper Climacteris picumnus, responded strongly over a short-term (20 mo) to a meso-scale (34 ha) manipulation of fallen-timber loads in river red gum Eucalyptus camaldulensis forest in northern Victoria, Australia [Mac Nally, R., Horrocks, G., Pettifer, L., 2002a. Experimental evidence for beneficial effects of fallen timber in forests. Ecol. Appl. 12, 1588–1594]. There were substantially more birds in all treatments in which loads were increased to 40 Mg/ha or more, elevated from averages of ca. 20 Mg/ha across the southern Murray-Darling Basin. Sites were revisited 3 years after the manipulation was conducted and I show here that the changes in density have been sustained. These results suggest that increased fallen-timber loads ≥40 Mg/ha are preferred by the vulnerable treecreeper, and that the bird's responses reported previously were not transient. These elevated densities may translate into increased reproductive success of the treecreepers because larger groupings in this and related cooperative breeders produce more young. I conclude by outlining options for management of fallen timber to provide greater chances of viability for the species.