Effects of plant species diversity and genetic diversity on belowground communities and processes

Background/Question/Methods

Biodiversity is a critical element of community properties and ecosystem processes.  Both plant species richness and genetic diversity positively affect processes ranging from primary production, ecosystem stability, and the maintenance of diversity.  In nature, it is likely that species diversity and genetic diversity interactively affect how communities are structured and ecosystems function.  However, their relative contributions and potential interactive effects have been rarely documented.  A potentially important (but relatively unexplored) consequence of declining plant diversity is the alteration of soil microbial community structure and function. Soil microbes are important drivers of ecosystem functions and can be important determinants of plant community structure. Here, we report results from a common garden experiment conducted in a coastal freshwater dune habitat at Sleeping Bear Dunes National Lakeshore in Empire, MI.  We manipulated plant species diversity (0, 1, 3, or 6 species) and genetic diversity (0, 1, 3, or 6 populations) within a dominant, dune-building species (Ammophila breviligulata) to address how both levels of diversity simultaneously influence soil microbial community structure and function. 

Results/Conclusions

Preliminary results suggest that plant diversity influences a wide range of belowground responses.  Soil nematode abundance doubled with both increasing species diversity and genetic diversity, although there were no interactions between the two levels of diversity.  Furthermore, there is a strong trend for plant species diversity and genetic diversity to interactively influence arbuscular mycorrhizal fungal spore abundance.  Soil physical properties were also affected.  Potassium was generally lost from experimental communities during 2009 to 2010. Potassium loss was greatest at high levels of species diversity. However, there was a significant species diversity by genetic diversity interaction such that in plots with high levels of genetic diversity, potassium was not lost, but instead increased with increasing species diversity.  These results suggest that interactions between levels of diversity are an important, but often overlooked, aspect of how diversity structures communities and mediates ecosystem processes.