The spatial dispersion of spores of vesicular-arbuscular mycorrhizal fungi in a sand dune: microscale patterns associated with the root architecture of American beachgrass

Abstract

In order to develop a model of the spatial dispersion of populations of vesicular-arbuscular mycorrhizal fungal (VAMF) spores within a root zone, we hypothesized that their spatial pattern would be correlated with the below-ground architecture (growth and structure) of the root system. Detailed excavation and mapping of the roots within the vicinity of three clusters of Ammophila breviligulata ramets (culms) revealed a network of rhizomes, many of which were not connected to the original plant. The species richness of VAMF for the three plots ranged from six to nine, including five genera. A high degree of spore clumping was not significantly correlated with the location of roots, nor with any of the physical soil parameters tested, or with the abundance of spores in adjacent sampling areas. The abundance of spores at a particular location in the soil generally was not a good predictor of spore populations only 10 cm distant. Since such spores are not readily dispersed from the point of sporulation, it is likely that some spore aggregations formed previously in association with fibrous roots that have subsequently decayed and are no longer detectable in the soil profile.