Growth and nutrition of three conifer species across site gradients of north coastal British Columbia

Abstract

We compared height growth and nutrition (foliar nutrient concentrations and retranslocation rates from 1-year-old needles) of second-growth plantations on imperfectly drained, lower productivity cedar–hemlock–salal forests with those of more productive ecosystems of north coastal British Columbia. Soils ranged from deep organic profiles to well-drained mineral soils derived from igneous to metamorphic bedrock. Leader increments on imperfectly drained sites were smaller than on well-drained sites, averaging 42% less for western hemlock (Tsuga heterophylla (Raf.) Sarg.), 56% less for Sitka spruce (Picea sitchensis (Bong.) Carrière), and 32% less for western redcedar (Thuja plicata Donn ex D. Don). Strong linear correlations were found between leader increment and foliar N, P, and S concentrations for all three tree species, and baseline foliar data for productive sites were presented. The foliar N ratios with P, S, and K were consistent across sites and indicated that many key foliar nutrients increased proportionally to the availability of N. A comparison of nutrient concentrations between current and 1-year-old foliage generally showed little difference on poorer sites, which suggested that there had been no retranslocation of nutrients from young needles within trees to compensate for low soil nutrient availability. This study confirmed the inherently low productivity of cedar-hemlock-salal forests, especially on granodiorite and gneissic diorite bedrock types, and suggested the need for site treatments or long rotations for sustainable management.