Switchgrass has various strategies for growing in low-nitrogen (N) environments, including translocating N to its roots during the winter and fostering a microbial community that can fix N. Switchgrass exhibits wide phenotypic and genotypic diversity, and we explored whether N translocation, fixation, and mineralization vary among cultivars. It does vary, with some varieties fixing N at high rates and also translocating a high percentage of their N. This information can inform selection of switchgrass varieties for biofuels cultivation. Varieties that conserve N do not require N fertilizers, making them more economically and environmentally sustainable.
Aaron Pelly and Erica Bakker successfully defended their MS theses last week, becoming the first two MS recipients from the lab! Aaron focused on the effects of water stargrass on ecosystem metabolism and dissolved oxygen concentrations in the Yakima River, and Erica measured nitrogen fixation in Cascades Mountains streams, examining both sediment bacteria and cyanobacteria. They presented from home to a geographically-dispersed audience and nailed their zoom presentations. Excellent job, Aaron and Erica!
Do you like rivers, microbes, plants, biogeochemistry, and/or agriculture? Are you looking for lab and/or field experience in environmental science or biology? Are you work-study eligible? If so, apply now for a work-study position in the Watershed Biogeochemistry Lab. I am looking for one work-study student to help with lab and field work during the 2019-2020 school year. Potential activities include: preparing reagents, weighing samples, entering data, preparing vials for gas analyses, washing glassware, collecting water and plant samples, pulverizing soil and plants, and packing samples for isotopic and elemental analysis.
More info: Work Study 2019-2020 Job Description
In our new paper, out in Soil Biology and Biochemistry, we used isotopic tracers in laboratory, greenhouse, and field settings to measure nitrogen (N) fixation in switchgrass. Our results suggest that bacteria associated with switchgrass fix N episodically – meaning fixation sometimes occurs at a high rate and is undetectable other times – perhaps in response to transiently appropriate physicochemical conditions. Metagenomic analyses revealed a wide diversity of bacterial taxa in and around switchgrass are capable of fixing N. We still don’t know if fixation is an important source of N to perennial grasses. If fixation is important in the switchgrass N budget, those inputs may occur in periodic bursts of fixation activity.
Citation: Roley, S.S., Xue, C., Hamilton, S.K., Tiedje, J.M., and Robertson, G.P. 2019. Episodic nitrogen fixation in switchgrass (Panicum virgatum L.). Soil Biology and Biochemistry.129: 90-98. doi: 10.1016/j.soilbio.2018.11.006
Undergraduate researchers Rhenton and Cassandra presented at the WSU Tri-Cities Sympoisum today. Rhenton showed results from his summer project, in which he evaluated nutrient limitation of microbial and algal biofilms in tributaries of the Yakima River. Cassandra presented results on the effects of common herbicides, 2,4-D and glyphosate, on algal and microbial biofilms.
Dr. Carmella Vizza recently started in the lab as a postdoc on the E-fix (episodic N fixation) project. Before joining the lab, she received her B.S. in Ecology and Evolutionary Biology at Tulane University in 2008 where her honors thesis was about spider sperm competition. Next, she worked as a project manager for four years at the Northwest Fisheries Science Center (NOAA Fisheries) based in Seattle, WA, examining the effect of marine-derived nutrients brought by Chinook salmon to riparian ecosystems. In 2018, she received her PhD at the University of Notre Dame in the field of aquatic biogeochemistry with the guidance of advisors Drs. Gary Lamberti and Stuart Jones. Her dissertation investigated how physicochemical properties and microbial communities shape ecosystem function in Alaskan wetlands.
Carmella is passionate about biogeochemistry and microbial communities, and looks forward to expanding these interests during her postdoctoral research. She will be shifting her focus to associative nitrogen fixation in switchgrass and is already hard at work, installing switchgrass mesocosms in Michigan!
Our upcoming project on N fixation in perennial grasses was featured in WSU news. Check it out:
Aaron Pelly and Erica Bakker will both be pursuing M.S. degrees in Environmental Science, starting in Fall 2018. Aaron comes to the lab with a B.S. in Environmental Science from WSU Tri-Cities and after completing a SULI internship at Pacific Northwest National Laboratory’s Marine Sciences Lab in Sequim, WA. He is interested in aquatic ecology, especially in research that contributes to tackling the ecological problems facing our world. Erica taught high school science and math in Washington and Oregon for several years and is excited to embark on a new phase of her career.
Congratulations to Rhenton, one of the 2018 Chancellor’s Summer Scholars! He is studying nutrient limitation of algal and microbial biofilms in the Yakima Watershed.
Phil Robertson, Dan Buckley, and I have received NSF funding to work on associative nitrogen fixation in perennial grasses! We will be using isotopic tracers to determine when nitrogen fixation occurs, estimate N inputs on an annual scale, identify the microbes fixing N, and examine the plant-microbe relationships underlying this process. Looking forward to this exciting, challenging project!