Forestcheck: the response of birds to silviculture in jarrah (Eucalyptus marginata) forest

Abstract

Summary In the five-year period from 2001 to 2006, 48 monitoring grids comprising the FORESTCHECK initiative were established in open eucalypt (jarrah, Eucalyptus marginata) forest in south-west Western Australia. Since 1985, revised silvicultural objectives have necessitated detailed monitoring of responses by bird species and assemblages to silvicultural treatments (timber harvesting and associated burning). Few marked changes in the avifauna were detected. Species accumulated (in terms of numbers of grids) at similar rates in gap release, shelterwood/selective cut, and reference (either never harvested or harvested more than 40 years previously) forests. In terms of individuals, species accumulated faster in the gap release forests. The number of species represented as singletons was greatest on the never harvested (8), coupe buffer (7) and gap release (6) grids. Dominance-diversity curves also showed only minor differences between silvicultural treatments. Neither nMDS nor CAP ordinations showed any clear separation between the treatments. There was little evidence of any substantial effect of silvicultural treatments on avian community structure or on individual bird species. Community structure was, however, significantly associated with forest ecosystem/year of sampling. The basal area of live trees was not correlated with bird species richness or abundance on each grid. These results are consistent with previous studies, which indicate that most bird species in jarrah forest have a high threshold level of tolerance to disturbance. It is likely that the rapid regeneration of dominant tree species after harvesting and associated fire, the patchiness of treatments at the landscape scale, the high degree of connectivity of harvested and burnt forests with forests not recently harvested or burnt, and the retention of habitat trees in the most heavily—harvested (gap release) forests all conduce to dampen local-scale impacts and conserve the avifauna in relation to the home range and normal movements of its constituent bird species.