Relationships between terrestrial vertebrate diversity, abundance and availability of coarse woody debris on south-eastern Australian floodplains

Coarse woody debris (fallen wood, CWD) has been largely stripped from both rivers and their floodplains in the southern Murray-Darling basin of south- eastern Australia. Some of our work suggests that as little as 20 t/ha (on average) remains on floodplains where once the figure may have been closer to 90-125 t/ha. Here we examine the consequences of this depletion of a pot entially significant habitat-structural element on the terrestrial vertebra tes of the floodplain forests. Three major forests were studied: Gunbower I sland, Barmah Forest and the Ovens River floodplain (all in northern Victor ia, Australia). In each forest, seven graded (by loads of CWD) sites were i nvestigated over 2 years. Our results show that the only native terrestrial mammal (yellow-footed antechinus Antechinus flavipes) occupies sites in si gnificantly higher densities when wood loads exceed 45 t/ha. Ground- and CW D-using birds are more prevalent, and in richer diversity, in the vicinitie s of accumulations of woody debris. Overall, fallen-wood loads do not appea r to relate significantly to avian patterns apart from at the local scale ( i.e. near wood accumulations). Neither frogs nor reptiles appear to be infl uenced by fallen-wood loads. These results suggest that restoration targets might reasonably be set at about 40 50 t/ha, but it seems that birds would be aided by the imposition of a high variance in CWD-load densities rather than an even distribution. Numbers of reptiles are very low, which may ref lect the very broad-scale depletion of fallen timber from these habitats; s imilar impacts may have been expressed in wood-depleted box-ironbark forest s immediately to the south of the floodplain forests. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.