Growth and physiological responses of Black Spruce (Picea mariana) to sites dominated byLedum groenlandicum.

Growth and physiological parameters of black spruce planted eight years previously were compared at sites with and withoutLedum groenlandicum to quantify the adverse effects on black spruce inLedum sites. Tree height, crown diameter, and dry weights of stems, branches, and needles of black spruce were significantly less at theLedum-dominated sites. Annual stem height, basal diameter, growth ring width, and cumulative wood volume of black spruce were significantly reduced in theLedum sites compared to those of the non-Ledum sites. Yearly growth of black spruce in the first seven years after planting was more affected in theLedum site than the eighth year's growth. Foliar nutrient analysis of black spruce in theLedum site showed an overall imbalance in nutrient accumulation. Black spruce growing in theLedum site had higher foliar concentrations of Al, Ca, Fe, Ni, and S and lower concentrations of N and Si than those growing in the non-Ledum site. Black spruce growing in theLedum site also had a higher foliar phenolic content. Preliminary experiments suggest thatLedum has the potential to leach water-soluble phenolics to its immediate organic soil.