We studied how species number and abundance of the understorey vegetation correlates with nutrient contents of soil and tree leaves at a northern boreal forest site. The phosphorus (P) content of the humus layer showed higher correlation with vegetation than the nitrogen (N) content. Usually N is considered more important in boreal forests. The plots with high P content in humus had birch as the dominant tree species, implying that birch leaf litter is an important source of P to the plants.