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Warra coupe WR001B, with retained mature trees shortly after logging. |
Image: Leigh Edwards |
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Warra coupe WR001B, with retained mature trees four years after logging. |
Image: Leigh Edwards |
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Project summary:
Several coupes in the Warra silvicultural systems trial have been harvested according to partial felling systems, either by dispersed retention (WR001B, WR008C), stripfell/patchfell (WR001A) or single tree/group selection (WR005D, WR008G). Monitoring of the persistence of retained trees began in 1997 (for dispersed retention coupes); monitoring in the single tree/group selection coupe began in 2003.
In the dispersed retention coupes approximately 10% of the original standing basal area was retained as dispersed trees, whereas in the stripfell 50% of the original forest was retained (for half a logging rotation) in two strips and a small (5ha) patchfell. Two belts of retained vegetation have thus been created plus there is a cut edge adjacent to Grants Creek at the western end of the coupe and a cut edge adjacent to Leighs Creek at the eastern end of the coupe. The two belts vary slightly in width; both are orientated roughly north – south, so that their edges face east and west. The edges and belts are assessed annually. The edges have proved susceptible to mechanical damage during the harvesting operation and during fireline construction. They also proved susceptible to fire damage during the regeneration burn, windthrow, myrtle wilt, death by exposure via increased insolation and drying winds in summer, and increased cover of some plant species (eg fireweed (Senecio spp.), Histiopteris, Hypolepis sp., bracken).
Methodology: The trees in the dispersed retention coupes were assessed immediately after the completion of harvesting to quantify damage to the retained trees caused by the harvesting operation, before this damage was masked by the regeneration burn. The positions of the retained trees were mapped so that subsequent windthrow can be monitored. The volume of the retained trees was measured so that their contribution (loss) to the overall productivity of the stand can be determined. The trees were assessed again after the regeneration burn to assess the impact of the burn on the retained trees and subsequently the trees were monitored quarterly for two years. The stripfell coupe was also assessed annually along edges and belts for windthrow and crown health.
Datasets: None available.
Publications: Neyland, M.G. (2004). Selection, harvesting damage, burning damage and persistence of retained trees following dispersed retention harvesting in the Warra silvicultural systems trial in Tasmania. Tasforests 15: 55-66.
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