Fauna assemblages in regrowth vegetation in tropical open forests of the Northern Territory, Australia

Context. World-wide, primary forest is in decline. This places increasing importance on understanding the use by biodiversity of regrowth (secondary) forest, and on the management of such regrowth. Aims. This study aimed to compare the terrestrial vertebrate assemblages in tropical eucalypt forests, regrowth in these forests (following clearing for pastoral intensification) and cleared land without regrowth, to provide evidence for developing management guidelines for regrowth vegetation in a region (the Daly catchment of the Northern Territory) subject to increasing demands for land-use intensification. Methods. The terrestrial vertebrate fauna was surveyed consistently at 43 quadrats sampling forest, 38 sampling regrowth and 19 sampling cleared land (formerly forest), and the faunal composition was compared with ordination and analysis of variance. Further analysis used generalised linear modelling to include consideration of the relative importance of disturbance (condition) of quadrats. Key results. Faunal assemblages in regrowth vegetation were found to be intermediate between cleared land and intact forest, and converged towards the faunal assemblage typical of intact forest with increase in the canopy height of the regrowth. However, even the tallest regrowth quadrats that were sampled supported relatively few hollow-associated species. The management of fire, weeds and grazing pressure substantially affected the faunal assemblages of the set of regrowth and intact forest quadrats, in many cases being a more important determinant of faunal attributes than was whether or not the quadrat had been cleared. Conclusions. In this region, regrowth vegetation has value as habitat for fauna, with this value increasing as the regrowth structure increases. The convergence of the faunal composition of regrowth vegetation to that of intact forest may be substantially affected by post-clearing management factors (including fire regime and level of grazing pressure and weed infestation). Implications. Regrowth vegetation should be afforded appropriate regulatory protection, with the level of protection increasing as the regrowth increases in stature. � 2009 CSIRO.