A decade of change in the saproxylic beetle fauna of eucalypt logs in the Warra long-term log-decay experiment, Tasmania. 2. Log-size effects, succession, and the functional significance of rare species

摘要

The first decade of sequential and cyclical sampling of the saproxylic beetles of twelve freshly felled Eucalyptus obliqua logs at Warra, Tasmania has allowed comparisons between larger-diameter mature and smaller-diameter regrowth log-classes and between successive sampling cycles and years; and consideration of the interplay between these two aspects. The two log-classes support different assemblages, with the mature log-class hosting consistently more species, more unique species, and proportionally more obligately saproxylic species. Assemblages change seasonally and year-to-year, demonstrating succession. While changes in the assemblages of mature and regrowth log-classes follow similar trajectories, they remain distinct at every point in time. These differences remain apparent when considering sub-sets of the assemblages based on the rarity of the species involved, their flightedness, saproxylicity and larval feeding guild. This study suggests a need to incorporate the conservation of coarse woody debris derived from mature trees into production forestry practices. There is a particular need to devise silvicultural and/or planning systems that cater for the retention and long-term recruitment of mature trees, since these are the only source of the larger-diameter logs that were identified in this study as having particular ecological value. Through continuing the Warra long-term log-decay experiment over the next century or more, a more complete picture of the saproxylic beetle fauna will progressively emerge, together with a better understanding of the management requirements of the fauna.