Soil microbial communities influence ecosystem development in Great Lakes sand dunes

Background/Question/Methods

Soil microbes play a critical role in shaping terrestrial ecosystems.  They influence soil development by facilitating nutrient cycling, soil aggregation, and the deposition of organic carbon.   Through their interactions with plants, they also influence plant community structure and dynamics.  Despite their general importance, few studies have investigated how soil microbes influence above- and below-ground ecosystem development in a single system.  Primary successional systems such as the Great Lakes sand dunes provide an ideal system for testing how soil microbes influence ecosystem development.  Great Lakes sand dunes are constantly being formed and older dunes remain, creating a chronosequence where successional patterns of plant communities and soil development are preserved along a gradient of ecosystem age.  Using soil inoculum collected from dunes of different ages at two different sites, I established a greenhouse experiment to test the following questions:  1) Is there evidence that soil microbes influence patterns of plant community succession?  2)  Do soil microbes from dunes of different ages differentially influence soil properties?  3)  Are these patterns consistent across space?

Results/Conclusions

There is evidence that plant-microbe interactions influence plant community succession in Great Lakes sand dunes.  Early successional plant species performed worse on early successional soils than bare sand soils, and mid-successional plant species performed worse on mid-successional soils than early successional soils.  These results suggest that the build-up of species-specific pathogens may be facilitating successional dynamics. There were site-specific differences in the responses - the effect of microbes on early successional species was stronger at the southern site and their effect on mid-successional species was stronger at the northern site.  Soil microbial communities also differed in the amount of extraradical hyphae they produced.  Extraradical hyphae are important for soil development and carbon sequestration.  The production of extraradical hyphae peaked in soil communities from mid-successional dunes, and soil microbes from the more southern site produced more hyphae than soil microbes from the more northern site.  Together, these results show that soil microbes influence above- and below-ground ecosystem development in the Great Lakes sand dunes.  Therefore, soil microbes should be considered in efforts to restore degraded dune habitats.