Structure Retention. PURPOSE To create temporary refuges for forest biota to re-colonize blocks. To maintain snags and live residual trees in harvested areas for species that depend on these structures following natural disturbances. To provide wildlife thermal and hiding cover within blocks throughout the rotation. To provide wildlife travel corridors within large blocks and compartments.
Structure Retention. PURPOSE • To create temporary refuge and habitat for forest biota associated with early seral habitat • To provide wildlife thermal and hiding cover within harvest units throughout the rotation. • To provide wildlife travel corridors within large harvest areas and compartments. • Create a forest structure that contributes towards the emulation of natural disturbance DISCUSSION Although many types of natural disturbance (fire, floods, wind events, pest events) occur within Alberta's forests, fire is the most common. Historically all trees are killed within intense fires but, following low and moderate-intensity fires, many scattered live trees are present post disturbance. In addition, within all fire types, fire skips result in residual patches of live trees remaining within burned areas. MPB has emerged as a threat to the forests of Alberta and as a result accelerated harvest levels have been approved. The concern about retention of pine trees creating refuges for MPB and exacerbating the spread of MPB has led to increased emphasis on the retention of non-pine species to compensate for the removal of pine. X. Xxxxxxx (March, 2001) suggests that fires in the boreal forest are commonly referred to as "events". They tend to be memorable, occur over a very short period of time, and leave behind a mosaic of burnt and un-burnt patches. The relationship between events and their constituent patches is vital to ANC Xxxxxx's approach to residual structure retention. An area relationship between patches and fire events exists. Since most events are composed of a number of disturbance patches, we expect large events to be even more prominent on the landscape. For instance, disturbance patches greater than 2,000 hectares occupy 71% of the Upper Foothills landscape, while disturbance events greater than 2,000 hectares occupy 90% of the Upper Foothills landscape (Andison, March 2001). It is not possible to create compartments with as high a density of large snags as are found after fire. However, retaining some large snags and large downed logs within harvest areas and compartments creates habitat for some of the biota associated with disturbed habitat. Additional large snags may be created by retaining large live trees, as some of these trees will die throughout the rotation. Current residual structure in the FMA area indicates that considerable opportunity exists for retaining residual structure post-harvest. Refer to Table 2-10 in the FMP for a summary of the categor...
Structure Retention. GROUND RULES
Structure Retention. Alberta-Pacific and Xxxxxxxxxx will leave an average of 5% merchantable volume for structure retention throughout the FMU. Structure retention will be left in the following methods: - Laid out patches - Individual trees
Structure Retention. DISCUSSION Retention of pre-harvest trees, snags, and woody debris within harvest areas is an important ecological value. It is a value related to local, stand-level biodiversity. Retaining mature trees within harvest areas increases the structural diversity of the regenerating stands and leads to both vertical and horizontal structure in the short and long term. It provides a level of old growth values over the early development of regenerating stands. In addition, stand level structure retention provides a variety of habitats which can be utilized by a number of boreal species.
Structure Retention. B12 FMU STRUCTURE RETENTION DISCUSSION Structure retention targets will be achieved using the following objectives:
