The effect of Kalmia angustifolia on the growth, nutrition, and ectomycorrhizal symbiont community of black spruce

Abstract

Kalmia angustifolia L. is an ericaceous shrub that frequently invades black spruce ( Picea mariana Mill.) clear-cuts in central Newfoundland. Field observations suggest that on many sites where K. angustifolia grows, black spruce seedlings become chlorotic and stunted. Previous laboratory research has suggested that allelochemicals of K. angustifolia affect the growth and development of black spruce as well as the growth of certain ectomycorrhizal (ECM) fungi associated with black spruce. Black spruce seedlings close to (<1 m) and far from (>1 m) K. angustifolia were sampled from a clear-cut in central Newfoundland. The ECM community structure, degree of mycorrhizal infection, height, mass, root:shoot ratio, and the foliar concentrations of N, P, K, Ca, and Mg of spruce seedlings growing close to and far from K. angustifolia were examined. Seedlings close to K. angustifolia had significantly lower foliar concentrations of N and P, had a lower rate of mycorrhizal infection, and were more frequently associated with Phialocephala dimorphospora Kendrick, a potential root pathogen of black spruce, than seedlings growing far from K. angustifolia. There were positive linear relationships between black spruce foliar N concentration and total seedling height and biomass for seedlings growing away from K. angustifolia, but not for seedlings in close proximity to K. angustifolia. Hypotheses suggesting possible roles for nutrient competition, allelopathy, and K. angustifolia's ability to increase the occurrence of the pseudomycorrhizal P. dimorphospora on black spruce are proposed.