Effects of nitrogen fertilization on the humus layer and ground vegetation under closed canopy in boreal coniferous stands.

Abstract

Forest ecosystems may accumulate large amounts of nitrogen in the biomass and in the soil organic matter. However, there is increasing concern that deposition of inorganic nitrogen compounds from the atmosphere will lead to nitrogen saturation; excess nitrogen input does not increase production. The aim of this study was to determine the long-term changes caused by nitrogen input on accumulation of nitrogen in forest soils and in ground vegetation. The fertilization experiments used in this study were established during 1958–1962. They were situated on 36- to 63-year-old Scots pine ( L.) and Norway spruce ( (L.) Karst.) stands of different levels of fertility. The experiments received nitrogen fertilization 5–7 times over a 30-year period, and the total input of nitrogen was 596–926 kg/ha.Pinus sylvestrisPicea abies