How organic farming alters soil & microbial communities over time
The research I am working on for my postdoc links soil nutrient pools with microbial communities to better understand soil processes in the context of organic farming soil management. I am analyzing soils from over 120 organic dairy farm fields in SW Wisconsin that have been under organic management for different lengths of time. I also conducted a greenhouse experiment to investigate the abilities of farm sourced microbial communities to decompose nitrogen fertilizers and make nutrients available to soybeans, corn, and rye. (postdoc research with Dr. Lankau, Dr. Erin Silva, and Dr. Matt Ruark.
The video below is a 3 min summary of these projects. |
Responses of alpine sedges to nitrogen deposition
A long-term nitrogen deposition simulation study at Niwot Ridge shows that elevated nitrogen availability has shifted the abundances of the dominant plant species. I explored potential mechanisms for the observed increase in Carex rupestris' cover and decrease in Kobresia myosuroides' cover. I tested whether aluminum toxicity, changes is soil bacteria composition or mycorrhizal fungi associations were involved in these sedge species responses to long-term N additions. I did not find support for bacteria or Al toxicity being responsible for changes in abundances of these sedge species. It is possible, however, that an ectomycorrhizal species, Cenococcum geophilum may be involved. (PhD study, Bowman Lab)
Publication: https://doi.org/10.1002/ecs2.2775 |
Linking plant traits and phylogeny to soil microbial community composition
Soil microbial community structure and function has been characterized for individual plant species, but do more closely related plant species have more similar affects on microbial community development near their roots? Does a change in nutrient availability disrupt or enhance the specificity of plant-microbial community interactions? I pursued answers to these questions using seeds and soils from 7 species in the common grass genus Poa. I used a greenhouse experiment to isolate the effects of nitrogen addition from the effects of root exudates (chemicals excreted by plant roots) on microbial communities. Poa species did have unique effects on some aspects of microbial communities and nitrogen addition did enhance differences among plant species as predicted. However, the patterns did not match up with plant species relatedness or traits. (PhD study)
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How vulnerable is the alpine to plant invasions?
Alpine ecosystems in the Rocky Mountains have yet to experience non-native species invasions (aside from common dandelion). The alpine has been impacted by invasive species in other regions of the world, but the factors that allow them to colonize and persist are not well understood. I conducted a survey of invasive species along roads that extended from montane to alpine ecosystems across Colorado's Front Range to identify which species are commonly found in the subalpine (below treeline). While the alpine is weed free, we found that a number of non-native species live right at tree-line!
I also conducted growth chamber experiments on invasive cheatgrass (Bromus tectorum). I tested whether anthropogenic nitrogen deposition could enhance cheatgrass' ability to establish and reproduce at different alpine growing season temperatures. Additionally, I tested whether N deposition and soil type influence cheatrass' ability to recover from simulated spring freezing events that are typical during spring storms in the alpine. I found that cheatgrass is resilient to low growing season temperatures and can even recover and flower after exposure to -8 °C. Interestingly, it was the alpine soil used in these experiments that inhibited cheatgrass growth and reproduction. (PhD study) Publication: https://doi.org/10.1007/s10530-020-02225-5 |
Cascading effects of top predators on plant communitiesIn the interim between undergrad and grad school, I managed a large study in the Blackfoot Valley, MT under PIs Dr. John Maron (University of Montana) and Dr. Dean Pearson (USFS). The goal of this 10-year study was to determine the indirect effects of top predators on plant communities. I managed several experiments which explored the roles of seed predation, small mammal demography, seed dispersal, competition, disturbance, and nutrient availability on plant community structure.
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