Mycorrhizal colonization mediated by species interactions in Arctic Tundra

URCELAY, C., M. S. BRET-HARTE, S. DÍAZ & F.S. CHAPIN III

OECOLOGIA

Springer-Verlag

Año: 2003 vol. 137 p. 399 - 404

0029-8549

The Alaskan tussock tundra is a strongly nutrient-limited ecosystem, where almost all vascular plant species are mycorrhizal. We established a long-term removal experiment to document effects of arctic plant species on ecto- and ericoid mycorrhizal fungi and to investigate whether species interactions and/or nutrient availability affect mycorrhizal colonization. The treatments applied were removal of Betula nana (Betulaceae, dominant deciduous shrub species), removal of Ledum palustre (Ericaceae, dominant evergreen shrub species), control (no removal), and each of these three treatments with the addition of fertilizer. After three years of removals and fertilization, we found that overall ectomycorrhizal colonization in Betula was significantly higher in the control than in removal and fertilized treatments. Changes in ectomycorrhizal morphotype composition in removal and fertilized treatments were also observed. These results suggest that the effect of Ledum on Betula mycorrhizal roots may be mediated by nutrient availability in the soil. However, we did not find a significant increase in nutrient availability, as measured by ion accumulation on resin bags, in the Ledum removal treatment. One possible explanation is that Betula may rapidly take up the nutrients made available by Ledum removal. In contrast, ericoid mycorrhizal colonization was not affected by fertilization, but the removal of Betula and, to a lesser degree, removal of Ledum, resulted in a reduction of ericoid mycorrhizal colonization, suggesting a direct effect of these species on ericoid mycorrhizal colonization