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Missing baseline information for British Columbia's forests : can timber cruise data fill some gaps? McHugh, Alyson Elizabeth


Assessing trends in forest ecosystems requires a thorough understanding of a benchmark or condition against which changes can be measured. Timber cruise information is a valuable source of baseline data, and has potential to be used in monitoring the effectiveness of management actions taken to maintain biodiversity and other societal values during and after harvesting. The objective of this study was to assess the efficacy of using these data as baseline information in FREP (Forest and Range Evaluation Program) Stand Level Biodiversity (SLB) assessments. Using three different data sources (timber cruise data, FREP pre-harvest data, and FREP post-harvest data), I conducted a pre- and post-harvest survey and evaluated trends in indicators within and across seven cutblocks. Mean densities for live and standing dead trees by diameter class, total live and dead trees, functional snags, large trees, tree species composition, coarse woody debris, and a number of qualitative indicators were analyzed. Results indicate that similarities exist between several characteristics within the timber cruise and pre- and post-harvest FREP data. For example, there was substantial overlap between stand structural characteristics assessed by the three methods. However, some discrepancies were identified. Large trees (live, dead and live and dead combined) were evident in very small numbers in the timber cruise and data were not consistent with pre-harvest FREP data. The number of tree species identified in FREP data was generally lower than timber cruise data, with the species absent in the FREP data generally being recorded as rare in the timber cruise. Some important stand structural attributes are not collected under the current timber cruise protocol. This research has identified some possible limitations of using timber cruise statistics as baseline information for FREP SLB monitoring. Forests are dynamic, rare forest elements may be misrepresented in all three samples, and some potentially valuable data are currently missing from timber cruise statistics. However, the opportunities that timber cruise data provide as a provincial baseline dataset are immense, and further exploration and study could identify ways to improve the compatibility, efficiency, and utility of these data in FREP Stand Level Biodiversity monitoring.

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