Postdoctoral Research
Shining light on the black box that is soil microbial carbon cycling
While most of the terrestrial net primary productivity enters the decomposition pathway and is returned to the atmosphere as carbon dioxide via soil microbial respiration, some detrital carbon is biologically stabilized in soil through the growth of microbial biomass. The amount of carbon that is ultimately stabilized in soil depends - in large part - on how effectively the soil microbial community converts carbon to biomass growth relative to how much carbon is lost as carbon dioxide due to respiration.
This is known as carbon-use efficiency
My postdoctoral research will make use of stable isotope methodologies to investigate the effects of soil moisture and substrate supply/availability on carbon-use efficiency of soil microbial communities in a variety of semiarid environments throughout the western US.
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How does soil moisture - partitioned into the effects of water content and water potential - and substrate availability influence soil microbial growth, respiration, and carbon-use efficiency across different soil textures?
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How do invasive species affect soil microbial carbon-use efficiency in semiarid grasslands of western Montana?
*In collaboration with Ylva Lekberg and Morgan Luce McLeod at MPG Ranch
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Many mason jars full of northern Utah dirt during a trial experiment that will help to address this research question
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Morgan Luce McLeod and John Stark discussing invasive plant ecology at MPG Ranch's Orchard House Experimental Plots.
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Other Ongoing Research
Nitrogen dynamics in tropical forests
I am fortunate to be part of a fantastic collaborative team seeking to understand the patterns and controls of nitrogen cycling across plot, landscape, and regional scales on the Osa Peninsula in Costa Rica. We use observational, experimental, and remote sensing approaches to link pattern with process and aboveground plant phylogeny with belowground nutrient availability.
Read more about our work here, here, here, here, and here.
*Collaborators: Cory Cleveland (University of Montana), Fiona Soper (Cornell), Stephen Porder and Brooke Osborne (Brown University), Alan Townsend (Colorado College), Philip Taylor (Mad Agriculture), Greg Asner and Chris Balzotti (Stanford), and Benjamin Sullivan (University of Nevada, Reno).
Read more about our work here, here, here, here, and here.
*Collaborators: Cory Cleveland (University of Montana), Fiona Soper (Cornell), Stephen Porder and Brooke Osborne (Brown University), Alan Townsend (Colorado College), Philip Taylor (Mad Agriculture), Greg Asner and Chris Balzotti (Stanford), and Benjamin Sullivan (University of Nevada, Reno).
Brooke Osborne (PhD candidate, Brown University), Alex Swanson (former undergraduate, Brown University) and I using GPS linked remote sensed hyperspectral imagery of the forest canopy (generated by the Carnegie Airborne Observatory) to determine where to establish some field plots.
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Philip Taylor (Mad Agriculture) sizing up the majestic Ajo tree (Caryocar Costaricense).
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Fiona Soper (Cornell) and Max Villalobos (Osa Conservation) getting excited about tropical tree seedlings.
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PhD Research
Tropical forests are critical drivers of Earth's climate due to their vast exchanges of energy, water, and nutrients with the global atmosphere. Yet, despite the well-recognized importance of this biome to the global climate, fundamental uncertainties remain in our understanding of the nutrient cycles that underlie the productivity and dynamics of these forests worldwide. One of the more interesting problems lies in the resolution of the nitrogen cycle. Though it is often assumed that lowland tropical rain forests are rich in nitrogen relative to phosphorus, they contain far more symbiotic nitrogen fixing trees than ecological theory would suggest.
My dissertation research explored how soil phosphorus may be playing a role in driving the abundance and activity of nitrogen fixing trees in tropical rain forests.
My dissertation research explored how soil phosphorus may be playing a role in driving the abundance and activity of nitrogen fixing trees in tropical rain forests.
An indeterminate nitrogen fixing nodule found in the forest reserve at Universidad EARTH (Escuela de Agricultura de la Región del Trópico Húmedo) in Guácimo, Limón, Costa Rica).
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Seedlings in the open-air greenhouse at the Greg Gund Conservation Center, Osa Peninsula, Costa Rica.
*This work was funded by a National Science Foundation Doctoral Dissertation Improvement Grant.
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3. Do nutrient availability and nutrient acquisition strategies mediate tropical tree growth under elevated atmospheric carbon dioxide concentrations?
An enriched atmospheric carbon dioxide mesocosm at the Smithsonian Tropical Research Institute's Santa Cruz Field Facility, Gamboa, Panama.
*This work was funded by a Smithsonian Tropical Research Institute Short-Term Fellowship & a National Science Foundation Doctoral Dissertation Improvement Grant.
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