In northern Scandinavia, shrubs expand into the tundra, where fixation of nitrogen from the air is mostly performed by cyanobacteria associated with mosses. Additionally, enhanced nitrogen fixation stimulates plant growth. New research shows that as taller shrubs expand into the tundra, nutrients in leaf litter will either promote or reduce nitrogen fixation, depending upon which shrub species dominates. The scientific results have recently been shown by scientists Kathrin Rousk and Anders Michelsen from Center for Permafrost and Department of Biology at University of Copenhagen, and is now published in Global Change Biology.