SYMP 10-2 - Ecological silviculture in the wet forest domain

Coastal forests in several temperate regions of the Pacific Rim are characterized by wet climates influenced by high seasonal rainfall from weather systems originating in the Pacific Ocean. These wet forest types include North and South American temperate rainforests, Douglas-fir – western hemlock forests of the US Pacific Northwest, and mountain ash (Eucalyptus spp.) forests of SE Australia. Similar but distinctive approached to ecological silviculture have emerged in this broad ecological domain over the past few decades guided by our increasing understanding of natural disturbances, stand development processes and the contribution of structural and compositional legacies to resilience, adaptability, and biodiversity. Approaches to ecologically based management seek a broader provision of ecological, cultural and societal benefits than traditional timber-focused models or even multiple-use and integrated resource concepts. Common attributes of these diverse forests include: significant areas of old growth forests with tall trees of large diameter that have some of the highest biomass per hectare in the world, and a history of clearcutting, resulting in abundant second-growth forest of high density and simplified structure. Tree species composition varies widely among regions, as does differing mixtures of public and private land ownership and tenure rights. Dominant natural disturbances range from predominantly small-scale, wind-initiated gap-phase dynamics in the temperate rainforests of N. and S. America, to infrequent high severity fires in SE Australia. These differences lead to specific applications and challenges for implementing ecological silviculture. For example, wind damage after harvesting in rainforests of SE Alaska and British Columbia favors use of variable retention with large aggregates, while the importance of fire for natural regeneration of eucalypts makes it difficult to distribute retention throughout regenerating areas in SE Australia. While many regions have adopted variable retention approaches, irregular shelterwood and selection systems are favoured in the evergreen forest type in Chile. Operational implementation of variable retention has been extensive in the wet forest domain on public lands in some jurisdictions, but it is still at the experimental stage in others. A common approach being used for restoration of structural complexity in dense second-growth stands is variable density thinning. Several long-term monitoring and research sites occur within this diverse domain to examine alternative silvicultural approaches.