Effects of Previous High N Addition on Nutrient Conditions in Above-ground Biomass of a Picea abies Stand in Sweden

Deposition of air pollutants, together with intensified harvesting practices, has led to concern about the declining base cation status and the acidifying effects in the soil, with possible implications for silviculture. The aim of this study was to analyse the effects of a previous high N addition on the nutritional status in the above-ground part of a tree stand. We sampled various biomass fractions in a highly productive Norway spruce (Picea abies (L.) Karst.) stand in the province of Värmland, western Sweden. The experimental plots had been fertilized with urea four times at intervals of 5 yrs, the last time being 13 yrs before our study. The total amount of N added was in the range 480-2400 kg ha^-1. Despite the high N addition and an insignificant growth increase following N input, there were no obvious residual changes of nutrient concentrations in the above-ground parts of trees.