Phosphorus Additions Increase the Early Growth of Red Alder (Alnus rubra Bong.) on Vancouver Island

Abstract

Abstract The effects of nutrient additions on growth of the red alder (Alnus rubra Bong.) are not well known. We examined the growth and nutritional responses of 10 young (0–4 years old at time of fertilization) red alder plantations on eastern Vancouver Island to additions of phosphorus (P), added as triple super phosphate, and a blended fertilizer (F) containing elements other than nitrogen (N), P, and calcium (Ca). Site fertility classes ranged from poor to very rich and soil moisture regime classes ranged from moderately dry to very moist. Nutrients were added in single-tree plots and responses were measured for up to 3 years after fertilization. In plantations fertilized within 1 year of planting, P additions increased heights (average of 17%), basal diameters (28%), and stem volumes (68%) over a 3-year period and increased 1st-year foliar concentrations of P, N, and S. The fertilizer supplying other elements also increased concentrations of N and S, along with potassium (K), boron (B), zinc (Zn), and manganese (Mn), but increased volume by only 16%. These data suggest that deficiencies of P are more likely to limit the growth of young red alder than are deficiencies of other elements. Older plantations (more than 2 years postplanting) were less responsive to fertilization than were younger plantations (less than 2 years postplanting). Growth of young red alder appears limited by P availability when soil Bray-P and foliar P concentrations are less than approximately 12 mg kg−1 and 2 g kg−1, respectively.