Inoculation with arbuscular mycorrhizal fungi, fertilization and seed rates influence growth and development of lyme grass seedlings in two desert areas in Iceland

The potential benefits of artificial inoculation with arbuscular mycorrhizal fungi (AMF) for lyme grass seedling establishment were tested in combination with varying fertilizer and seed rates in a long term revegetation study in two sandy deserts in Iceland. Fertilizer inputs proved more effective than other treatment variables in increasing vegetative growth, flowering and sand accretion of lyme grass seedlings. For this, re-fertilization was more important than the initial dose. AMF inoculation initially improved seedling growth but after the first year the effects became neutral or negative. While fertilization generally reduced AMF colonization, the negative effects of inoculation on lyme grass were enhanced by fertilization. Larger seed doses raised interand intraspecific competition, decreasing lyme grass vegetative regeneration and associate vegetation. Based on the current results, the application of AMF inoculation cannot be recommended for lyme grass establishment at the present. However, low seed rates (≤50 seeds m-2) and low initial fertilizer doses (≤10 g m-2) in combination with moderate re-fertilization application rates for a few years are apparently economical for the establishment of lyme grass for revegetation projects.