Differences in growth and nutrient uptake from a coarse-soil substrate by ectomycorrhizal- and fungicide-treated Picea abies seedlings

In order to quantify the importance of ectomycorrhizal fungi on nutrient uptake from the coarse-soil fraction of a haplic Cambisol (alumic), a microcosm study that allowed for nutrient budgets was designed. Ectomycorrhizal- and fungicide-treated spruce seedlings were grown on isolated and cleaned gneiss fragments (6.3 mm > Ø > 2 mm) from 90 cm soil depth. The substrate was the only source of Ca, K and Mg. Ectomycorrhizal seedlings showed no signs of nutrient deficiencies and biomass increased significantly compared to initial seedling biomass. Ectomycorrhizal seedlings seemed well adapted to survive on the coarse-soil substrate and acquired Ca, K and Mg from the coarse-soil substrate. Gneiss fragments of the ectomycorrhizal treatment were covered by fine roots and ectomycorrhizal hyphae, as observed microscopically. Fungicide-treated seedlings’ root development was retarded, and shoot biomass only increased from stored nutrient reserves of the seedlings. The suppression of EcM colonization by the fungicide Topas® apparently caused a root growth inhibiting effect. Furthermore, the extinction of mycorrhiza initiated an increased nitrification and acidification and a consequent nutrient cation release triggered by nitrate in the drainage.