Crecimiento y colonización micorrícica de Polylepis australis Bitter (Rosaceae) en suelos con distinta historia de pastoreo

large herbivores directly affect plant performance through biomass removal, but also through indirect effects on plant-fungi symbiotic associations and soil fungal communities which have been less studied. we hypothesized that soils from sites with different domestic european herbivore densities would affect growth and arbuscular mycorrhizal colonization (amf) of polylepis australis bitter (rosaceae). in order to examine the indirect effects of livestock density through their signals in soil, we evaluated in the greenhouse the growth and amf colonization of p. australis seedlings grown in soils belonging to sites with three domestic herbivore densities (null, low and high). we also measured initial amf spore density and composition together with soil properties. after 5 months, p. australis dry mass was higher in soils collected from the treatment without grazing and lower in seedlings grown in soils with low and high livestock densities. in contrast, mycorrhizal colonization was marginally higher in roots at the high livestock density treatment, intermediate at low density and lower in roots from the treatment without livestock. these results do not seem to be related to soil properties and initial amf spore composition, since there were no significant differences in soil chemical properties between sites while spore richness and density were similar in soils with null and high livestock density. our results suggest p. australis growth and mycorrhizal colonization may be mediated by complex soil food web interactions which add to herbivore direct effects of clipping or removing of biomass.