|
A larva of a scirtid beetle in a wet crack in a log. |
Image: Marie Yee |
|
Eucalyptus obliqua log showing the red-brown muddy rot type common in larger diameter logs. This rot type supports a distinct assemblage of invertebrates. |
Image: Marie Yee |
|
White stringy rot, a common type in smaller diameter Eucalyptus obliqua logs. |
Image: Marie Yee |
|
Project summary:
Marie Yee’s PhD thesis abstract: Large diameter Eucalyptus obliqua decaying logs are characteristic features of unmanaged wet eucalypt forests in Tasmania. In production coupes, however, rotation lengths of around 80 years will eventually lead to their elimination. This thesis investigates the role of these features as habitat for saproxylic beetles, and thus whether their retention is warranted to maintain biodiversity.
Two field studies were conducted, in which a highly species rich fauna of 360 saproxylic beetle species (representing 54 families) are first recorded:
The first, destructive sampling study, investigated whether small diameter logs follow similar decomposition processes to large diameter logs, and so support similar rot types and beetle assemblages. Eleven rot types were differentiated, each associated with a particular region within the log. Small diameter logs had a relatively high incidence of white rot towards their outer edges, probably originating from fungal colonisation after treefall. Large diameter logs had a higher incidence of brown rot towards their cores, probably originating from internal decay already present in older, living eucalypt trees prior to treefall. Some of the beetle species characteristic of this brown rot are possibly poor dispersers and may be of particular conservation concern in production forests.
The second, log emergence trapping study, examined the extent to which beetle assemblages differ between small and large diameter logs, and whether they respond in the same way to forest successional processes induced by stand level disturbance. Distinct suites of species were associated with large logs irrespective of forest type, yet there were few small log specialists. Assemblages differed significantly between the mature and logging regenerated forests; there was also significant variation among sites that could not be attributed to forest type. Small diameter logs in the logging regenerated forest lacked some apparent mature forest specialists that were present in large diameter logs in the same forest type; and, they also hosted the fewest species.
The research indicates that large diameter logs are probably important in providing continuity of habitat for the re-establishment of certain species following stand level disturbances, whether induced by logging or by wildfire. A degree of landscape-level planning in Tasmanian forestry is recommended that would maintain large diameter logs in the production forest landscape indefinitely.
This project complements another project at Warra that is monitoring saproxylic invertebrates in logs from the beginning of the decay process. Download a pdf (2.3Mb) of a PowerPoint presentation given at Forestry Tasmania in March 2005
Methodology: Large diameter (>100cm) logs derived from commercially over-mature trees were compared with small diameter (30-60cm) logs derived from trees of an age approaching commercial maturity, in two forest types: mature, unlogged forest; and 20-30 year logged forest that had regenerated after clearfelling.
Datasets: None available.
Publications: Grove, S.J. (2009). A decade of deadwoodology at Warra. The Tasmanian Naturalist 131: 25-35.
Wardlaw, T., Grove, S., Hopkins, A., Yee, M., Harrison K. & Mohammed, C. (2009). The uniqueness of habitats in old eucalypts: contrasting wood-decay fungi and saproxylic beetles of young and old eucalypts. Tasforests 18: 17-32.
Yee, M. (2005). The ecology and habitat requirements of saproxylic beetles native to Tasmanian wet eucalypt forests: potential impacts of commercial forestry practices. PhD, University of Tasmania, Hobart.
Yee, M., Yuan, Z.-Q. & Mohammed, C. (2001). Not just waste wood: decaying logs as key habitats in Tasmania’s wet sclerophyll Eucalyptus obliqua production forests: the ecology of large and small logs compared. Tasforests 13: 119-128.
|
