Walker Lab Disturbance and Ecosytem Ecology
People
Faculty
Xanthe Walker
Xanthe Walker is an Assistant Professor at Northern Arizona University’s Center for Ecosystem Science and Society. She is an ecosystem ecologist interested in understanding the impacts of environmental change and disturbance on the structure and function of northern terrestrial ecosystems. She has experience in disturbance ecology, dendrochronology, statistics, and the application of stable and radioactive carbon isotopes.
Email: xanthe.walker@nau.edu
Michelle Mack
Michelle Mack is a Regents Professor at Northern Arizona University’s Center for Ecosystem Science and Society. See Mack Lab for more information.
Email: michelle.mack@nau.edu
Research Associates
Hillary Cooper, PhD
Hillary is an evolutionary ecologist broadly interested in species’ response to global change. She has studied the combined effects of drought and invasive species throughout the Southwest, with an emphasis on how intraspecific differences in traits and trait plasticity affect adaptation to rapid environmental change. Her current work focuses on nutrient cycling in response to disturbances such as pest outbreaks and fire in the boreal forest.
Email: hillary.cooper@nau.edu
Zach Madsen, MSc
Zach is a plant ecologist with a background in alpine spatial ecology, particularly the influence of snow on plant communities and landscape-scale vegetation patterns. In his current role, he contributes to boreal forest research in Alaska, leading dGPS-based subsidence monitoring and data quality control efforts across post-fire field sites.
Email: zacharaih.madsen@nau.edu
Olivia Hajek, PhD
Post-doctoral Researcher
Olivia is a plant and ecosystem ecologist whose research examines how climate variability and extremes reshape ecosystem structure and function. Her current work in the boreal forest investigates the development of understory plant communities after wildfire and explores how shifting climate and disturbance regimes are altering tree growth and forest demographics.
Email: olivia.hajek@nau.edu
Camille Butkus, MSc
Lab Technician
Camille is interested in understanding the biogeochemical processes responsible for the movement and transformation of nutrients in plants, soil, and water. Her prior work focused on soil nitrogen and carbon cycling in agricultural and riparian contexts.
Ian Stepanek
Lab Technician
Ian has broad experience working across different Alaskan ecosystems to understand carbon cycling. He is currently implementing large-scale fuel break treatments to assess disturbance impacts on permafrost soil C pools and fluxes in the black spruce forests of Interior Alaska.
Graduate Students
Nicholas Link
PhD Student
Nick is a PhD candidate studying how ecological succession plays out in fuel breaks across Alaska and Yukon. His work is helping create nature-based solutions to increasing wildfire risk across the region.
Anastasia Pulak
PhD Student
Anastasia is a PhD candidate studying how wildfire-induced changes in vegetation impact soil carbon accumulation and turnover.
Bjorn Larson
PhD Student
Maya Chandar-Kouba
PhD Student
Maya’s current research is based in Interior Alaska, where she studies how wildfires impact nutrient cycling, carbon storage, and below-ground structures across plant communities. She has previously worked at the Harvard Forest LTER and the Toolik Field Station.
Abby Hay
PhD Student
Abby is studying tree regeneration after disturbance in Interior Alaska. Specifically, her research examines how the pathogen causing aspen running canker will impact successional trajectories.
Andrew Haverdink
Master’s Student
Alumni
Post-doctoral Associates
Jeremy Forsythe, PhD
Jeremy studies the drivers and impacts of wildfire in the boreal forest using satellite remote sensing products and machine learning models. Specifically, he seeks to assess where and when reburning occurs and determine the consequences of reburning for post-fire successional trajectories throughout the northwestern North American boreal forest.
Email: jeremy.forsythe@nau.edu
Graduate Students
Felecia Amundsen, MSc
Thesis: Impacts of fuel reduction treatments on the ecology of wild blueberry (Vaccinium uliginosum) and cranberry (V. vitis-idaea) species in Interior Alaska
Matthew Behrens, MSc
Thesis: Fires Footprint: Understanding soil heating and fire effects in Denali National Park & Preserve’s prescribed pile burns
Savannah Wilson, MSc
Thesis: Drivers of fire severity in western North American boreal deciduous forests
Sonja Noomah, MSc
Thesis: Fuel reduction treatmens reduce hazard trees in spruce-beetle affected stands in Alaska
Betsy Black, MSc
Thesis: Drivers of fire severity in western North American boreal deciduous forests
Ellery Vaughan, MSc
Thesis: Nitrogen and phosphorus limitation of plant productivity and ecosystem carbon storage changes with post-fire succession in an Interior Alaskan boreal forest