|Intermediate utilization (IU) practices used during the early era of harvesting in the Prince George Forest District (PGFD) from about 1950 to 1970, have 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 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 combined evaluation of diameter distributions by number of stems and volume also seemed to suggest that the Bl-IU stratum had a higher proportion of smaller diameter trees, and fewer larger diameter trees. 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. There was a trend of increasing frequency of old growth attributes as stands increased in age, based on a first approximation to assign a rating of old growth characteristics to each sample. However, the list of old growth attributes used in this report is not complete, and the preliminary old growth criteria may need to be revised for the stand types in the PGFD. The results of this study are considered interim, since only 15 of the targeted 24 old stratum samples had been sampled by the end of 2006. The remaining nine old samples are scheduled for establishment in the summer of 2007. Since the sample size of the old stratum is incomplete, the results should be re-run following the establishment of the remaining nine phase II plots in the old stratum.|
prepared by Timberline Natural Resource Group Ltd.