Throughout the Pacific Northwest of Canada and the United States, an ecosystem approach to forest management is being adopted. A common definition of ecosystem management involves the recognition that provision of diverse benefits from forests may be achieved by allowing natural processes to occur or by emulating natural processes through management. Forest management regimes that emulate natural disturbances (e.g. mountain pine beetle (MPB) outbreaks, wildfires and windthrow events) leave standing green and dead trees, as well as variable levels and structural complexity of woody debris. In many disturbance events, some pockets of residual live trees are often left, depending on the severity of the disturbance and tree species composition. This pattern of patchy natural disturbance that leaves live trees as individuals and in clumps forms the basis for green-tree retention. In terms of ecosystem management, green-tree retention leaves large live trees after harvest to persist through the next rotation to increase structural diversity of the regenerating stand and provide mature forest habitat that develops sooner than in typical even-aged management by clearcutting This structural diversity retains some later seral conditions such as a multi-layered canopy, provides a future supply of large snags and down logs, and may increase microsite variability for a more diverse understory. This proposal fits Research Priority 1.4: Effectiveness of stand-level structures and habitat in maintaining biodiversity; specifically Question 3: What are the appropriate stand-level targets and configurations of stand-level structures in cutblocks in order to maintain biodioversity? A MPB outbreak in the mid-1970?s in the southern interior of B.C. resulted in relatively widespread salvage logging of lodgepole pine from mixed pine ? Douglas fir stands and mixed pine ? western larch stands. In pine-leading stands, fir or larch are left as residual standing trees. These 'seed trees' provide a source of fir regeneration to provide a secondary species to lodgepole pine, which regenerates naturally from abundant cone slash. This is a relatively widespread practice that has been in place since the early to mid-1970's when lodgepole pine became an important commercial timber species. Thus, this form of green-tree retention is not a new management approach to salvage or conventional timber harvesting in this region. Because of this relatively long history, it is possible to do a retrospective investigation of the influence of harvesting lodgepole pine on stand structure and biodiversity 30 years after cutting. Stands with residual green trees, composed of dispersed to aggregated Douglas fir with understory lodgepole pine, cover several landscapes in the southern interior, having arisen from harvesting over the past 30 years. Thus, a major question is: how do these stands compare to those uncut in terms of stand structure and development of late seral forest conditions? This question has direct relevance to sustainable forest management for wildlife habitat and biodiversity. Stand structure and the responses of several mammal groups will be used as indicators of sustainability and biodiversity. Examples of these species and groups are the masked shrew (Sorex cinereus) and the southern red-backed vole (Clethrionomys gapperi) on the forest-floor and the northern flying squirrel (Glaucomys sabrinus) in the arboreal mammals, and mule deer (Odocoileus hemionus) in the large mammals.
Sullivan, Thomas P.. 2007. Stand structure and maintenance of biodiversity in green-tree retention stands at 30 years after harvest: a vision into the future. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2007MR334