Black spruce reforestation in Kalmia heath: seedling response to forest floor mixing and mycorrhizal inoculation with Paxillus involutus

Abstract

In the boreal forests of eastern Canada, black spruce ( Picea mariana (Mill.) Britton, Sterns, Poggenb.) regeneration often fails in nutrient-poor sites dominated by Kalmia angustifolia L. occurring after nonsevere forest fire, clearcut harvesting, and insect defoliation. Traditional silvicultural treatments have limited success in regenerating these sites. We tested whether forest floor mixing and planting black spruce seedlings preinoculated with an ectomycorrhizal (ECM) fungus, Paxillus involutus (Batsch) Fr., has potential to improve black spruce growth in Kalmia -dominated sites. We measured growth and foliar nutrient concentrations of ECM-inoculated and control black spruce seedlings planted in burned and insect-defoliated sites after forest floor mixing in Terra Nova National Park, Newfoundland. We also measured soil moisture, temperature, pH, total phenol and nutrient concentrations, litter decomposition, and soil respiration in those sites. Seedlings in soil-mixed plots had significantly higher growth and foliar nutrient concentrations than nonmixed plots, likely because soil mixing improved the substrate conditions by increased soil moisture, pH, and litter decomposition. Seedlings in insect-defoliated sites had significantly higher increases in height and foliar nutrient concentrations than those in the burned sites. Inoculated seedlings had significantly higher initial ECM formation than the control seedlings, but they failed to achieve higher growth.