Fine root development and mycorrhization in Norway spruce stands one year after fertilization with potassium sulphate and wood ash

Abstract

We compared the effects of forest fertilization with wood ash and potassium (K) sulphate on growth and mycorrhizal colonization of fine roots and on other soil microorganisms in Norway spruce (Picea abies) stands with symptoms of foliage damage. Fertilization trials with the application of 0.25 kg·m-2 of wood ash and similar amount of K as K sulphate were established. One year later, a total of 270 soil samples with roots were collected to determine morphological parameters of fine roots and extent of mycorrhization. Soil samples were collected to characterize soil chemical composition and number of colony forming units (CFU) of soil bacteria and fungi. The results showed that fine root biomass, length and volume, and relative abundance of living root tips were significantly higher in control sample plots than in treated plots. Abundance of bacterial CFU was higher in both wood ash and K sulphate treatments than in control plots; the Actinobacteria were more common in plots fertilized with wood ash than in other treatments. Relative abundance of several fungal species in sites fertilized with wood ash differed significantly from control sites and from sites fertilized with K sulphate.