Darian N Smercina
Linus Pauling Postdoctoral Fellow
Pacific Northwest National Lab
Long-term and Short-term N effects on Free-living Nitrogen-Fixation and Diazotroph Community Composition and Function
Switchgrass (Panicum virgatum), an important bioenergy crop, harbors a diverse rhizosphere community of free-living N-fixing bacteria (diazotrophs) which, as is becoming increasingly clear, are actively fixing N. This highlights the strong potential for switchgrass to rely on FLNF as an important N source, particularly when grown on low N marginal lands. However, it is not known how fertilization (long-term or short-term) impacts diazotroph community composition or function. Through a reciprocal N-addition greenhouse study , this project focused on answering questions about diazotroph community composition and FLNF rates under long-term and short-term N additions in different soils. Check out our recent publication in FEMS Microbiology Ecology for more!
Optimizing Methods for Assessing Free-living Nitrogen-Fixation in the Rhizosphere
Free-living Nitrogen-Fixation (FLNF) is an important and ubiquitous process in soils across ecosystems. While science has known about FLNF for over a century, it has often gone overlooked because this process wasn't thought to contribute much N to terrestrial systems. However, this is changing and it is becoming increasingly clear the FLNF happens all over and contributes a significant amount of N to terrestrial systems. The acetylene reduction method and N2 incorporation methods are commonly used to study FLNF. This project focused on optimizing conditions of this assay for the rhizosphere microbial community. Check out our publication in Plant and Soil for more!
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This DOE funded project (DE-SC0014108) is focused on understanding how plant-microbe interactions drive carbon and nitrogen exchange in the rhizosphere. Focusing on the bioenergy crop, switchgrass (Panicum virgatum), this project aims to answer questions about how interactions between the switchgrass rhizosphere microbiome, switchgrass root exudate chemistry, and plant traits may drive nitrogen availability in marginal lands over wide spatial and temporal scales.
My part in this project focuses on understanding the roles of free-living nitrogen fixation and nitrogen mineralization in driving soil and plant nitrogen availability. Check out the MMPRNT website for more info on the project and to see what others in the MMPRNT crew are up to! Also, check out our project videos here, here, here, and here!
Microbially Mediate Perennial Rhizosphere Nitrogen Transformations (MMPRNT)
The Effects of Climate Change on Stem Respiration
Darian Marinis (1), Andrew Reinmann (2), and Pamela Templer (3)
(1) University of Toledo, Dept. of Environmental Sciences; (2) Boston University, Dept. of Earth and the Environment; (3) Boston University, Dept. of Biology
How does changing climate impact stem respiration in the northern hardwood forest?
Anthropogenic climate change has led to increased year-round air temperatures and decreased snow cover in the northeastern United States. These changes are projected to continue and result in warmer soils during the growing season and greater frequency of soil freeze-thaw cycles during the winter. Dr. Pamela Templer’s lab has established the Climate Change Across Seasons Experiment (CCASE) to replicate climate change at the Hubbard Brook Experimental Forest in New Hampshire. Our goals were to quantify the (1) impacts of climate change and (2) interspecific variability on stem respiration. We measured stem respiration across the three CCASE treatments (reference, soil warming, and soil warming + freezing) and on four tree species (red maple, sugar maple, eastern hemlock, and American beech).
This work was completed as an REU summer project through NSF and Boston University's Summer Undergraduate Research Fellowship (SURF) program
Characterizing Soil Properties for Restoration Assessment
Darian Marinis (1), Todd Crail (1), and Michael Weintraub (1)
(1) University of Toledo, Dept. of Environmental Sciences
Can soil properties be used as restoration assessment metrics for the dry sand prairie plant community?
Oak Openings, a globally unique region stretching from Southeast Michigan to Northwest Ohio, is home to the critically endangered and globally rare dry sand prairie plant community. Dry sand prairie, a disturbance maintained plant community, once occupied 60% of the Oak Openings region but, due to human activities only 1% of dry sand prairie remains today, Dry sand prairie is a major focus for managers in the region because of its critically endangered state. Current restoration assessment methods typically overlook soil properties, which strongly influence plant community structure. The goal of this research was to characterize the soil properties of the dry sand prairie plant community in order to provide managers with another method of restoration assessment.
This work was completed as my undergraduate honors thesis and was funded through the University of Toledo Undgraduate Summer Research and Creative Activites Program (USRCAP) and the Office of Undegraduate Research.