An important element of landscape biodiversity is the spatial and temporal distribution of similar stands, or patches, on the land base. Natural disturbance regimes (fire, pests, disease, windthrow, etc) have heavily influenced the current mosaic of patch sizes and ages on the land base. The pattern and timing of forest harvesting is now the dominant influence on landscape patterns. In order to protect biodiversity, it is important that forest management strive to achieve similar landscape patterns to what would occur naturally. However, it is also important to recognize that a complete mimicking of natural patterns is not always desirable because the extremes are not always compatible with management for other resources (visuals, water quality, recreation etc) and may cause wide fluctuations in economic activity. Thus, a balance between natural landscape patterns and socio-economic objectives is necessary.
Ecosystems in the province have been grouped into Natural Disturbance Types (NDTs) that reflect their underlying natural disturbance regimes . The frequency and size of disturbances created by each natural disturbance regime influences the patterns that emerge on a landscape. Each NDT therefore has a characteristic patch size distribution. For example, large fires are the predominant disturbance mechanism in NDT 3A resulting in larger patches being more common within this NDT. NDT descriptions and recommended patch size distributions can be found in Section 2.1.
Concern in British Columbia over the fragmentation of existing old forests was previously raised with the implementation of the Forest Practices Code because of the legislated maximum cutblock sizes. This legislation generally resulted in smaller harvest openings dispersed across the landscape. The Forest and Range Practices Act (FRPA) and associated Forest and Range Practices Regulation (FPPR) sets out similar default practices for maximum cutblock sizes (FPPR Section 64 & 65) while also offering flexibility around creating larger openings based on biodiversity patch management.
The results of this project and the related management guidance will help rationalize the spatial and temporal pattern of future harvest openings in order that targets for patch size can be achieved.
Patch size targets are only one of many factors that must be considered when proposing harvest so the information in this report must be considered in light of any other resource values present in an LU. For example, issues such as terrain stability, avalanche concerns, recreation/visual concerns, etc. may force smaller openings to be implemented when larger ones are suggested by the patch size targets. Salvage logging associated with fires or insect infestations may skew patch distributions toward larger patches.
Forsite Consultants Ltd.. 2009. Biodiversity Patch Size Distribution Analysis for Adams Lake and Lower Adams LUs Kamloops TSA. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2009MR276
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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