The three major components in the site classification of the biogeoclimatic ecosystem classification system are: climatic regimes, soil moisture regimes (SMRs) and soil nutrient regimes (SNRs). Both SMRs and SNRs can be identified in the field using soil characteristics and indicator plants. In the case of SMRs a quantitative classification was also developed that allow comparison of SMRs in different subzones. However, similar quantitative classification has not yet been developed for SNRs. This pamphlet summarizes and compares the results of several regional studies conducted in different biogeclimatic zones. Each of theses studies aimes to develop a quantitative SNR classification (Table 1). The comparison will examine: (1) how well the field-based classification matches quantitative classification, and (2) which direct measures distinguish best between field-identified SNRs.

Subalpine fir (Abies lasiocarpa [Hooker] Nuttall) and white spruce (Picea glauca [Moench] Voss) trees were sampled in an old growth forest in the northern Canadian Rocky Mountains. Dendroclimatological methods were used to analyse the relationship between annual radial-growth and climatic variability. The white spruce ring-width chronology showed stronger sensitivity to climatic variability than the subalpine fir chronology. Both chronologies were positively correlated with growing season mean and minimum temperature. Additionally, the white spruce chronology was correlated with summer maximum temperature, late spring minimum temperature, and diurnal temperature range during the growing season. The subalpine fir ring-width chronology was also correlated with maximum and minimum temperature and diurnal temperature range during the during the previous winter and with the Pacific Decadal Oscillation during each month from December to June. Analysis of the climate-growth responses of individual trees revealed a higher level of intraspecies variability in subalpine fir than in white spruce. The white spruce chronology was selected for use in creating a proxy climate record based on its greater length and stronger sensitivity to climatic variability. Dendroclimatological methods were used to create a regional proxy record of June-July mean temperature extending back to 1772. This reconstruction exhibits a shared pattern of low-frequency variability with other dendroclimatic reconstructions from western Canada and shows no evidence of the recent reduction in sensitivity to climatic variability that is apparent in many other northern spruce chronologies. This study represents the first detailed dendroclimatic analysis undertaken in northern interior British Columbia. This work has elucidated the complex interactions between climate and the radial growth of alpine conifers in the northern Canadian Rocky Mountains. The climate reconstruction presented here fills in one of the remaining spatial gaps in the coverage of annually resolved climate reconstructions in western North America.