Effects of exponential fertilization on red spruce seedlings and ectomycorrhizas in various forest soil mixtures

Miller, Bradley

The endangered southern Appalachian spruce-fir forests have been negatively affected by exotic pests and excessive timber harvests. Reforestation efforts to rapidly expand this endangered ecosystem may require nursery production of red spruce seedlings with indigenous ectomycorrhizal (ECM) fungi. Previous research has shown that exponentially increasing fertilization regimes, compared to conventional regimes, has produced nutrient-loaded seedlings while increasing ECM colonization with commercially cultured fungal inocula. The goal of this study was to determine if exponential fertilization of red spruce seedlings in native forest soil and peat mixtures would produce nutrient-loaded seedlings while increasing ECM colonization and diversity by indigenous fungi. The ECM morphotype diversity of the red spruce seedlings was similar under exponential and conventional fertilization. Five indigenous ECM fungi, commonly found in elevated N environments, accounted for greater than 98% of ECM root tips after two growing seasons. The percentage of ECM short roots(PESR) of the spruce seedling was reduced at the highest fertilization levels. Exponential fertilization of spruce seedlings in control growing medium produced nutrient loading seedlings. Seedlings grown in spruce soil inocula increased N and P concentrations but not seedling total nutrient content or biomass. Exponential fertilization did not increase ECM diversity or colonization. All seedlings grew at least 15 cm tall, the minimum height required to survive out planting in an open field. The results of this study show that red spruce seedlings can be inoculated with ECM fungi from native forest soils and raised in a greenhouse under conventional fertilization.

Effects of exponential fertilization on red spruce seedlings and ectomycorrhizas in various forest soil mixtures

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