Initial quantitative characterization of soil nutrient regimes. II. Relationships among soils, vegetation, and site index

Relationships between soil properties, understory vegetation, foliar properties, and site index were examined in some Douglas-fir ecosystems on Vancouver Island. Multivariate summaries of variation in understory vegetation and foliar properties were highly correlated with the soil properties (mineralizable N, total N, and exchangeable Ca and Mg) that best characterized soil nutrient regimes of the ecosystems. The increases in soil nutrient availability were correlated with increased foliar N concentrations of the current year foliage. A consistent correlation was found between increased soil nutrient availability (particularly N, Mg, Ca) and decreased foliar Mn and Al. Site index of Douglas-fir was significantly greater on sites with greater quantities of most nutrients (particularly N, Mg, Ca) when sites with equivalent soil moisture regime were compared.