Assessing the Fertilization Response Potential of Subalpine Fir (Abies lasiocarpa): A Retrospective Study

Preand post-fertilization tree growth in unfertilized and fertilized thinned stands was used to estimate the 7-year radial growth response of operationally fertilized subalpine fir (Abies lasiocarpa). Despite large stem growth variability in thinned, and thinned and fertilized stands, the 7-year growth increment of fertilized trees was apparently 51–57% larger than the estimated growth that would have occurred had the stand not been fertilized. These results are consistent with the favourable fertilization responses reported for other Abies species. Reliable growth and yield data from well-designed fertilizer experiments are needed to provide a stronger basis for statistical inference of fertilization response and to provide area-based growth response estimates for subalpine fir. In the interim, however, some operational fertilization of subalpine fir may be justified, especially in vigorous, well-spaced (i.e., not overly dense) immature stands with a moderate component of nutrient-deficient interior spruce.