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Developing Baseline Data of Tree Species Composition in Unmanaged and Managed Forests by BEC Zone/Subzone/Variant in the Mackenzie Defined Forest Area
The value of British Columbias forests as simply a source of fiber has, in recent times,
been replaced with a more comprehensive view of economic, social, and environmental
values. Maintaining forests within their long-term range of natural variation with respect
to stand composition and age structure is an approach that may support the preservation
of many non-timber values. The forest species composition of old naturally regenerated
forest, and young stands that coincide with the advent of harvesting activities on the
Mackenzie DFA, provides both baseline information to guide future silvicultural
prescriptions and insights into current departures from natural conditions. Archived data
from the Landscape Unit Planning process, and recent data from Vegetation Resource
Inventory sources were used to define historic (unmanaged) and recent (managed)
forest species compositions, categorized by grouped BEC units and timber supply land
classifications.
Results for the unmanaged stand composition analysis met general expectations of greater representation of fir and less representation of pine in upland BEC units, with less fir and more pine on lowland BEC units. For unmanaged stands, representation of deciduous species was much greater on the non-contributing land base compared to the contributing land base. Overall, tree species composition of unmanaged stands on the Mackenzie DFA was 31% spruce (434,549 ha), 31% pine (426,660 ha), 28% fir (396,150 ha), 8% deciduous (117,115 ha) and 1% other species (17,963 ha). A comparison of unmanaged and managed stands occupying the THLB revealed that managed stands were composed of more spruce and deciduous species at the expense of pine and fir species. For the NCLB, the most consistent difference between unmanaged and managed stands was the greater representation of deciduous species on managed stands. Overall, tree species composition of managed stands was 40% spruce (59,753 ha), 29% pine (43,888 ha), 18% deciduous (26,918 ha) and 13% fir (18,775 ha) with negligible amounts of other species. Results also indicated that managed stands were composed of a lesser percent in essentially pure pine (i.e. =90% pine) stands and a greater percent in essentially pure spruce stands than unmanaged stands.
