Nutrient controls on ecological succession of microbial communities

Background/Question/Methods

Microbes are fundamental to soil physical and chemical development and underlie ecosystem function, thus understanding the factors that drive soil microbial community succession is key to predicting and managing ecosystem development.  While research has recently demonstrated patterns of succession in microbial communities, even before plant establishment, the mechanisms that drive these patterns and related function remain unknown.  Some evidence suggests that shifts in nutrient availability may, in part, drive microbial community succession. Yet other edaphic properties also undergo concomitant shifts with microbial community structure and function during succession, some of which are known to strongly correlate with microbial community structure such as organic carbon (C) pools and pH.  In order to directly test the role of nutrients in driving microbial community assembly over succession we established a full factorial nitrogen (N) and phosphorus (P) fertilization plot experiment in recently deglaciated (~3 years since exposure), unvegetated soils of the Puca Glacier forefield in Southeastern Peru.  Combined with standard analyses of soil edaphic properties and pyrosequencing of 16S rRNA genes, we evaluated the effect of such treatments on early successional microbial communities and in comparison to microbial communities across the natural successional chronosequence.

Results/Conclusions

Over the course of a single year, our nitrogen and phosphorus fertilization experiment caused bacterial communities of 3 year old soils to converge with soil communities that had undergone 85 years of natural successional processes. Our research therefore reveals that nutrient availability is a dominant mechanism in determining when and where particular microorganisms are present during different successional stages.  Our data also support recent evidence for the stability of soil microbial communities, as fertilization simply accelerated succession and did not push communities into a novel state. Thus, this research has implications for understanding how disturbances may change the structure and function of soil ecosystems and therefore a variety of ecosystem services.  Finally our work suggests that microbial ecophysiology with regards to nutrient availability may be predictive in understanding microbial community assembly and function across succession, an important foundation to ecosystem development.