Who we are


 jesse headshot

Jesse Nippert
Associate Professor

My research focus is on plant eco-physiological responses to changes in water availability (spatially, temporally, or driven by climate changes). Particularly, I'm interested in the mechanims of drought tolerance by grassland and savanna species (structure / function) as well as the theory of competition/ facilitation for water between trees and grasses. Thus, I enjoy spending my time addressing questions linking resource availability - physiology - patterns of productivity, with the goal of improving our ability to scale energy dynamics and hydrological processes from the plant- to ecosystem-level.

Personally, count me among the prairie dogs, meadowlarks and the bison; I [heart] grasslands. These systems exist within an interface of climatic variability and frequent disturbance (fire and grazers). Grass species are deceptively simple, but their unique physiology and form is adapted to environmental stress and disturbance. Despite abiotic and biotic pressures, grasses can grow like weeds (har har har) and develop dense canopies and high biomass. The environmental and biotic complexity of grasslands provides a challenging (mentally and physically) and enjoyable system to study. There is nothing better than spending a day on the Konza Prairie in the Kansas sun.

CV (last updated - May, 2012)


Amy Concilio
Post-doctoral Research Associate

My research focuses on plant community responses to global environmental change with an emphasis on interactions between native and invasive species.  Currently, I am studying plant responses to climate change and nitrogen deposition in the Front Range of Colorado, where both winter precipitation and nitrogen availability have increased in recent decades.  My work will examine how native and invasive plants in this system compete for water and how changes in precipitation and nitrogen availability might affect species interactions.  I also maintain active long-term research plots in the eastern Sierra Nevada (where I worked on my dissertation) to measure plant community response to increases in nitrogen deposition and changes in snowpack.

My primary home is at CU - INSTAAR, but every now and again I'll make the trip east to Manhattan.


Zak Ratajczak
PhD Candidate
personal webpage

One of the most fundamental characteristics of terrestrial ecosystems is whether they are dominated by grasses, trees, or a mix of the two. Studying tree-grass interactions brings up many interesting questions: How have grasses come to dominate such a large portion of the globe, even though their modern form only evolved ~8 million years ago? Why don’t trees expand into areas where they would enhance productivity? And how should we expect the balance of tree-grass competition to change as we alter the atmosphere and climate at unprecedented rates? My dissertation research focuses on understanding what determines the levels of grass vs. tree dominance in grasslands and savannas, with the goal of trying to predict how the dominance of these two functional groups will respond to different global change scenarios. This works draws heavily from plant eco-physiology and theoretical community ecology.

Grasslands and savannas play a very important role in many humans’ lives, providing food and a number of other ecosystem services. They also house unique plants and animals that cannot be found anywhere else. For these reasons, I’m also interested in studying the human and non-human forces that alter the biodiversity and productivity of grasslands and savannas.

CV (last updated - Aug, 2013)


Kim O'Keefe
PhD Candidate

My research investigates how physiological mechanisms of plant water-use drive larger scale ecological phenomena such as plant survival and productivity, patterns of species coexistence, and earth-atmosphere exchange of fluxes in grasslands. For example, I am linking root structure with water-use patterns (multi-scale hydrological fluxes), understanding mechanisms of competition and facilitation for water among coexisting species, and predicting the responses of these processes to hydrological variation associated with global climate change. For my dissertation I am using whole-plant sap flux and stable isotope techniques in a tallgrass prairie to ask the following questions: (1) What are the biological and/or environmental drivers of hydraulic redistribution? (2) Do patterns of hydraulic redistribution differ among functional types (shrubs, forbs, and grasses) and ecological gradients (topography and grazing treatments)? (3) How does this mechanism influence competition and facilitation for water among different functional types? (4) How does hydraulic redistribution influence landscape-level carbon and water fluxes? I am also intersted in other hydrological fluxes in this system (night-time transpiration), as well as identifying the adaptive significance of drought avoidance (hydraulic redistribution) versus drought tolerance strategies, particularly in the context of global climate change.

CV (last updated - Aug, 2013)


Gracie Orozco
Undergrad - Senior (6th year)
Dual Major: Biology / Environmental Engineering

Gracie started working in the ecophys lab as a freshman and is now our senior resident. She is from Kanopolis, KS (pop: 492), which is famously known for Orozco's Portales Cafe (best Mexican food in KS). Gracie's interests are focused on ecohydrology and modeling atmo-plant-soil flux dynamics. She has experience running environmental sensors, and using stable isotopes as predictors of ecological processes. Her other skills include singing out loud with the radio while working in the lab.


Ben Ketter
Undergrad - Senior
Major: Biology

Ben started working in the lab in the summer, 2012. Ben is the most energetic person in the lab, always ready for a challenge! He spent the summer 2013 as a REU student on Konza comparing tracer vs. natural abundance techniques to investigate hydrualic lift. He's taking those skills and an interest in belowground plant interactions to Columbia, MO to work with Ricardo Holdo


Rachel Lease
Undergrad - Junior
Major: Biology

Rachel started working with us in Jan., 2014. Rachel was originally interested in pre-Med, but thankfully realized how boring life would be as a "real doctor" (now she's interested in ecology). So far, she has helped with chores in SIMSL and assisted Kim with her research. Going forward, Rachel will be designing her own research project (presumably on plant physiology) as she gains experience for grad school.


Former Graduate Students

Troy Ocheltree (2008-12) Ph.D. - Agronomy and SIMSL Manager
Assistant Professor, Dept. Forestry and Rangeland Stewardship, Colorado State University

Jeff Hartman (2009-11) M.S. - Biology
Currently: University of Nebraska-Lincoln (w/ David Wedin)

Sally Tucker (2009-10) M.S. - Biology
Currently: Oklahoma State University (w/ Gail Wilson & Janette Steets)

Jacob Carter (2008-10) M.S. - Biology
Currently: University of Kansas (w/ Joy Ward)

Former Undergrads

K-State Students
Laura Kemp (2011-2012) - scientist at The Land Institute in Salina, KS
Whitley Jackson (2008-2012) - now at KU-Med School in KC
Teall Culbertson (2008-2011) - now a VetMed student at K-State

REU Students
Annie Klodd (2011) from Grinnell College
Rachel Wieme (2010) from St. Olaf's College
Zak Ratajczak (2009) from Vassar College
Laura Kangas (2008) from Michigan Tech

  Last Update: 13-Feb-2014