At Indiana University Bloomington, I am part of the Phillips Laboratory which broadly studies how plants and soil microbes alter nutrient dynamics in forests. I am interested in how free-living microbes and mycorrhizal fungi affect trees in the face of drought. Specifically, I aim to see whether microbes are adapting, acclimating, or undergoing community shifts in response to long-term drought, which can help them confer physiological benefits to their adjacent trees.

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For my first experiment, I investigated whether soil microbes exposed to reduced moisture in the past affect the sensitivity of hardwood trees to experimentally-imposed drought. I hypothesized that trees growing in soils with a history of dry conditions will experience less water stress in subsequent drought events due to the upregulation of drought resilience mechanisms in the microbial communities. To test this hypothesis, I employed a nested factorial drought experiment in the greenhouse using tulip poplar, chokecherry, and red oak seedlings. I planted seedlings in either field soil exposed to ambient moisture conditions or field soils exposed to a 55% reduction of moisture (relative to ambient) for 5 years. Then, I exposed the trees to either weekly or biweekly watering regimes for 10 weeks and quantified weekly changes in photosynthetic assimilation rate, stomatal conductance, stem elongation, and stem diameter. In a subset of time periods, I measured soil and leaf water potential to determine plant water-use strategies for each treatment combination. I am currently working on finding C:N and concentrations of nonstructural carbohydrates in the trees' roots, shoots, and leaves, as well as investigating root morphology and mycorrhizal colonization percentage. Results coming soon!

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Principal Investigator- Richard Phillips, Ph.D.

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