OOS 30-2
Adaptation above and below ground: How plants and rhizosphere microbes respond to global change
Both plants and their associated rhizosphere microbial communities respond strongly to global changes ranging from nitrogen deposition to climate change. In many cases, the responses aboveground may influence interactions with belowground microbial communities, and reciprocally, changes to belowground microorganisms may influence aboveground biota and even how plants respond to global change. Here I synthesize findings from two case studies that illustrate how ecological and evolutionary changes to belowground microorganisms influence plant responses to global change. I first use a 22-year nitrogen addition experiment and the classic legume-rhizobium mutualism as a model system to illustrate the capacity for soil bacteria to rapidly evolve in response to nitrogen deposition and show how evolutionary changes in this important belowground microbial taxa affect aboveground plant communities. Then, I use experimental evolution approaches in greenhouse mesocosms to show how community composition changes in belowground microbial communities help protect plants from the negative effects of climate change.
Results/Conclusions
In both case studies, the evolutionary and ecological changes to belowground microbes influence how their aboveground plant partners respond to global change. In the case of an important resource mutualism, the evolutionary changes occurring in belowground rhizobial populations increase the negative effects of nitrogen deposition for leguminous plants. In the case of diverse, general soil microbial communities, drought induced changes in soil microbial community composition help plants to maintain fitness in even harsh drought conditions. Together these results show how responses belowground can either intensify (rhizobia) or mitigate (general soil microbial communities) the negative effects of global change on aboveground systems.