Relationships among arbuscular mycorrhizal fungi, vascular plants and environmental conditions in oak savannas

We studied the relationships of plant and AMF (arbuscular mycorrhizal fungi) species richness and community composition to each other and gradients in soil texture, nutrient content, and light availability in three oak savannas in southern Wisconsin, USA. Sixty-three samples were analysed for plant and AMF composition along sun-shade and sand-loam gradients. Samples consisted of plant community composition at quadrat and point scales, point-scale AMF community composition, canopy transmittance, soil Kjeldahl nitrogen (N) content, available phosphorus (P), and texture. Numbers of AMF and plant species at the point scale were positively correlated with each other and increased with soil texture/N content. The compositions of plant and AMF communities were also significantly correlated with each other and the soils gradient. The paradoxical increase in AMF richness on the most fertile soils may reflect their small soil pores or low P : N ratios. Plant and AMF communities appear to respond to underlying environmental gradients in similar ways, perhaps reflecting similar responses to soil conditions by both groups, effects of one group on the other or both.