Ectomycorrhizal fungal community response to a water availability gradient

Background/Question/Methods

Complex environmental gradients consistently demonstrate that water availability is a key driver of plant species distribution and productivity and is important to microbes, such as bacteria and fungi. Environmental gradients, including water availability gradients, also influence outcomes of biotic interactions between plants and microbes.  However, reported outcomes of plant-microbe interactions along water availability gradients are diverse and the abiotic drivers of microbial community structure are equally varied. At Cedar Creek LTER, MN, 13 native species of Salix co-occur in niche-partitioned guilds along a water availability gradient. Salix spp. are hosts to ectomycorrhizal fungi (EMF) and arbuscular mycorrhizal fungi; these mycorrhizae interact with plant species through various pathways including nutrient exchange, abiotic stress mitigation, and pathogen defense. This study examined the response of EMF community structure to a complex hydrological gradient and to host species identity. To achieve this aim, we sampled roots from six common Salix species at Cedar Creek along an established hydrological gradient from upland to lowland habitats and identified EMF species using the ITS DNA region.

Results/Conclusions

Preliminary results show EMF species richness decreased across an increasing water availability gradient (upland=12.5±2.1, midland=9.0±2.8, lowland=4.0±2.6). We found evidence that EMF species composition shifts along the water availability gradient, where Tomentella taxa dominate at higher water availability and Cortinarius taxa dominate at lower water availability. Early evaluation indicates that EMF colonization negatively correlates with increasing water availability. Overall, EMF taxa do not correlate strongly with host species identity. These results indicate that water availability strongly influences EMF community structure and that EMF show little specificity toward Salix species, thus host identity is not an important driver of EMF community composition in this system. These data will provide a basis to experimentally investigate the mechanisms of hydrological effects on EMF community structure and plant-mycorrhizal interactions.