Foliar nutrient characteristics of four conifer species in the interior Northwest United States

This article provides foliar nutrient concentration distributions and sample size calculations for Douglas-fir, grand fir, ponderosa pine, and lodgepole pine. Managers can obtain foliar nutrient values from their own lands and use this information to make judgements on the relative nutrient status of forest stands. Foliage was collected from unfertilized trees at 160 different research sites of the Intermountain Forest Tree Nutrition Cooperative spanning a 16 yr period from 1982 to 1997. Douglas-fir showed the lowest variation in foliar nutrient concentrations, while grand fir was the most variable of the species sampled. Nitrogen was the least variable and Mn and Mo generally the most variable elements for all species. Grand fir had much higher foliar concentrations of K and Ca than other species. Ponderosa pine had the highest foliar N concentrations. The pines generally have lower nutrient concentrations than the firs, with the exception of Zn. Western hemlock habitat types showed lower Douglas-fir foliar Ca, Mg, and B concentrations, but higher K concentrations than other habitat type series. Douglas-fir growing on soils derived from meta-sedimentary rocks generally had lower foliar nutrient concentrations than those growing on other rock types.