Twenty-year growth results reported for a series of trial sites in southeastern British Columbia indicated that interior spruce progeny, regardless of seed origin, grew faster (32%, on average) and survived better (8%, on average) on acidic soils than on calcareous (high pH) soils. This previous study indicated that the soil chemical conditions (including calcareous soils) appeared to have considerable influence on the growth and survival of interior spruce. We investigated the soil relationships further on these sites in the current study. We could not explain a mechanism to account for the poorer tree growth, nor elucidate a regional trend regarding the specific influence of calcareous material on nutrient availability and/or how it may influence tree growth. However, trends (albeit insignificant due to within-site variability) were apparent on shallow calcareous soils, such as at the East White River site, where the carbonates were present within 30 cm of the surface and there was a trend for poorer growth when the trees were growing in these soils. There was no clear indication if nutrient deficiencies or imbalances were the cause. We also observed that the strength of carbonate (i.e. % CaCO3) was also greater on the shallower depth to carbonate sites. However, at the Lussier River site, where carbonates were on average deeper than at East White River, there was no trend in tree growth related to carbonate depths. Comparisons of the foliage chemistry between the two calcareous sites and an acidic site showed higher calcium (Ca) and magnesium (Mg) concentrations in the foliage from the calcareous sites; however, no differences appeared to be related to a carbonate-induced nutrient deficiency. We hope studies under way on fertilizer trials and the Long-Term Soil Productivity (LTSP) network sites in the East Kootenays will provide further insight into the role of carbonates on tree growth and the sensitivity of calcareous soils to disturbance. This study adds to the knowledge base, indicating that shallow calcareous soils are more sensitive to disturbance. Thus, management practices that minimize the potential detrimental effects of forest operations on calcareous soils should be implemented.
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Updated March 11, 2009