Intermediate Utilization (IU) practices used during the early era of harvesting in the Prince George Forest District (PGFD) from about 1950 to 1970, has resulted in residual stands dominated by subalpine fir (Bl). Most of these Bl-IU stands are not considered eligible for achieving old growth and biodiversity targets because of their indicated age in the inventory. Many forest practitioners believe some of these Bl-IU stands have characteristics of old growth, but there is no information to quantify their characteristics or compare with other stands considered old growth. This study provided a quantitative assessment of the differences between Bl-IU and old-aged stands, to help determine if Bl-IU stands can provide old growth requirements.
The comparison of old growth attributes between the Bl-IU and old stratum in the PGFD showed some significant differences, where the old stratum had the largest diameter trees, the oldest trees, the larger average tree diameter, and fewer stems, relative to the Bl-IU stratum. The observed differences between strata are likely due to a combination of past harvesting activities, limitations in sampling design to capture old growth attributes, and limitation in the sample population definition to capture all Bl-IU stand types. Conversely, some structural attributes were similar between the two strata (stand basal area, height of the tallest tree, total volume and CWD). The lack of significant differences between height, volume and CWD distributions suggests these attributes are either similar between the two strata, or that there is too much stand variability to identify significant differences. Overall, the results suggest that inventory age alone may be insufficient to quantify old growth in Bl-IU stands because inventory age underestimates stand age in the Bl-IU stratum. Accounting for this age underestimate suggests that at least 50% of Bl-IU stands may be old enough to be considered old growth. In addition, the frequency of other structural and size attributes also suggests that over 50% of the Bl-IU stratum includes characteristics that are similar to those found in old growth stands.
The Provincial Non-Spatial Old Growth Order provides options for stands not currently old enough, to meet old growth requirements if it can be demonstrated that they provided similar conservation value. The results of this study suggest that at least half of Bl-IU stands have similar characteristics to old growth, and therefore provide the necessary conservation values of old growth.
This report replaces an interim analysis previously completed in 2007 to quantify Bl-IU stands, and updates the analysis results following completion of the PGFD Phase II VRI field sampling program.
Timberline Natural Resource Group Ltd.. 2009. Quantifying Old Growth Characteristics of Balsam IU Stands Update Analysis. Forest Investment Account (FIA) - Land Base Investment Program. Forest Investment Account Report
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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