In the model, the photosynthetic nutrient use efficiency (PNUE) had a key role in determining
whether mycorrhizal strategy would be optimal for the plant net carbon gain. The model generated
several colonization patterns depending on possible changes in PNUE and soil nutrient
concentrations along altitudinal gradients. Field studies indicated that species-level colonizations do
not yield a consistent pattern along the altitude except for fine endophyte, which increased along an
altitudinal gradient. In a high-alpine field site root fungal colonizations were rare. Seasonal shifts in
colonizations in low-alpine conditions were not found. DSE fungi were common root-associates in
the field. In the laboratory, AM had a positive impact on the performance of Gnaphalium norvegicum
at 15°C, but not at 8°C. DSE-inoculation did not colonize the roots, but it had a positive impact on
seedling performance, which may be due to the saprophytic activity of the fungus in the substrate.
Additionally, mycorrhizal inoculum was found to decrease the performance of a non-mycorrhizal
plant in a competition experiment.