Silvicultural recovery in ash forests following three recent large bushfires in Victoria

摘要

The contrasting regeneration outcomes of alpine ash (Eucalyptus delegatensis) and mountain ash (E. regnans) forests (collectively called ash) after the extensive and severe 2003, 2006/07 and 2009 bushfires in Victoria demonstrate the complexity of factors that influence the establishment of ash regeneration after bushfire. About 189 000ha of ash forest was killed or severely damaged by the three bushfires, which burnt a land area totalling over 2.6 million ha. Silvicultural recovery work included aerial sowing of about 7100ha of fire-killed regrowth in state forests with about 6400kg of seed. This regrowth was less than 15-20 years of age and thus too immature to bear effective quantities of seed to achieve natural self-regeneration.This article includes a brief description of ash regeneration silviculture, a summary of relevant statistics for each of the three fires under consideration and the silvicultural recovery programs. Aspects of the recovery programs for the fires, including strategic seed-crop assessments, seedbed assessments, seed collection and management and aerial sowing operations are described, and their results are provided and discussed. The concept of ecological stocking', where regeneration levels are less than those required for commercial timber production, is also discussed.The natural seedling stocking levels resulting from the 2003 bushfires, which affected mostly alpine ash forests, were generally very satisfactory in stands of seed-bearing age. In contrast, after the bushfires of 2006/07, both natural and artificially sown eucalypt regeneration levels were often below commercial forestry standards. Natural stocking levels after the 2009 fires were again very satisfactory.