Landscape Attributes of Interior Douglas-fir Forests on the Fraser Plateau
A study was conducted to document the composition and spatial pattern of a forested landscape in the Interior Douglas-fir Biogeoclimatic Zone on the Fraser Plateau in central British Columbia. Geographic Information System analysis of Ministry of Forests' inventory data was used to document the landscape attributes for an 1800 km2 area. The study reconstructed a "natural reference landscape" to model what the area would have looked like in the absence of forest harvesting. The analysis revealed a natural reference landscape dominated by a matrix of older Douglas-fir and lodgepole pine forests covering 64% of the total land area. This matrix is highly connected and contained in large patches with approximately 70% of the older forest types found in patches greater than 1000 ha in size. Within this matrix are smaller patches of spruce, aspen and immature forests. Also within this matrix are numerous wetlands, small lakes, and surrounding meadow and shrub vegetation areas. These brushy, wetland and meadow areas are usually relatively small, averaging six ha, but can sometimes form larger connected complexes. Analysis of interior verses edge of combined older forest polygons revealed that 52% of the forested area in the natural reference landscape is made up of older forest far enough from edge effects to be classified as interior forest.
The study also documented attributes of the current landscape. In comparison to the natural reference landscape, the older forest matrix of the current landscape makes up a smaller amount of the total area (28%), has a smaller proportion of patches greater that 1000 ha ( 18%), and has less interior forest (13% of the total forest area). Comparisons between the current and natural reference landscape provide useful information about general trends but should not be interpreted as precise estimates of the change in landscape attributes resulting from forestry development. Limitations in this type of study include the level of accuracy of the forest inventory database and the inability to include the effects of fire suppression in reconstruction of the natural reference landscape. Despite these limitations, the study results provide useful information about trends in changing landscape composition and spatial pattern which can serve to flag potential issues of concern for timber, wildlife and biodiversity resource managers.
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