The effects of micro-scale spatial variation in soil biota containing arbuscular mycorrhizal fungi on plant competitive ability.

Variation in the soil biotic communities containing arbuscular mycorrhizal (AM) fungi may occur at micro-spatial scales and may influence the outcome of plant competition in old-field communities. Two competing plant species, Trifolium pratense and Plantago lanceolata, were grown in a greenhouse at varying densities in soil biota containing AM fungi collected from 9 spatial locations within a 30 x 30 m old field. T. pratense aboveground biomass varied with the spatial location of inoculum collection, but P. lanceolata aboveground biomass did not. Total leaf apparent chlorophyll content and percent arbuscule colonization did not vary with the spatial location of inoculum collection. Competition occurred for both plant species, but competition was only influenced by competitor density and not by the spatial location of inoculum collection. These findings suggest that while micro-scale spatial variation in soil biota containing AM fungi may exist in old-field ecosystems, it does not significantly impact the outcome of plant competition.