Ecohydrology for me is a blend of “contemporary forest hydrology” and “contemporary hillslope hydrology”. Prior to Ignacio Rodriguez-Iturbe’s field-defining commentary in Water Resources Research in January 2000, hillslope hydrology was decidedly non-ecological in its approaches. His commentary brought focus to the links in space and time between climate, soil, and crucially, vegetation. This is the essence of ecohydrology to me. While certainly broader definitions exist, this is how I have viewed it in the context of my own work on the age, origin and flowpaths of storm runoff. I am old enough to remember an AGU Hydrology Section that existed before the additional of an Ecohydrology Technical Committee. As Past-President of the section, it’s been a delight to watch this group lead the section on so many levels with such enthusiasm especially from the committee’s early career members. Go LEAFS! Coincidently, that was also my chant growing up as a fan for the Toronto Maple Leaf hockey team.
What are your undergraduate and graduate degrees in?
I came very close to doing an undergraduate degree in music. I even took a year off to contemplate the decision. Realizing that for me music should remain a hobby and not a career path, I started off my undergrad with interests in geology and geophysics at University of Toronto. Following a summer job as a geophysics technician in the Yukon, with several close encounters with grizzly bears, I came back to Toronto and changed my major to physical geography. The following two summers I worked as a SCUBA diver and eventually my interests moved from coastal geopmorphology to hydrology. I mention all this because I think that students starting out need to know that many of us have followed meandering, exploratory paths. I talk about this in a recent mentoring book (shameless self-promotion alert!). My MSc was in the Watershed Ecosystems Program at Trent University in Ontario. It was a joint Physical Geography-Biology degree. My MSc advisor, Colin Taylor, was a Kiwi. He encouraged me to do my PhD in New Zealand, following up on an ongoing controversy at the Maimai watershed. I went, and worked with Andy Pearce at the NZ Forest Service with a focus on Forest Hydrology, with my PhD from the University of Canterbury.
How did you arrive at working in/thinking about ecohydrology?
My interdisciplinary collaborations in ecohydrology started well after my PhD when I started working with collaborators coming from geochemical and biogeochemical backgrounds: Carol Kendall and Rick Hooper. Those interactions opened my eyes to new ways of looking at hillslopes and headwater catchments. Then, when I was an early career faculty member at SUNY-ESF in the 1990s, Myron Mitchell, Charlie Hall and Charlie Driscoll graciously let me in to their biological and biogeochemical worlds. I learned much from them. At Oregon State University, where I taught from 1999-2012, I found the HJ Andrews LTER site a rich environment for incubating ecohydrological thinking. There, I started working with plant physiologists. I learned much from Barbara Bond—a plant physiologist with exceptional patience for a hydrologist who, then, barely knew the difference between xylem and phloem. So too, I learned a lot from Renee Brooks with her unique blend of plant physiology and isotope geochemistry. Together, these colleagues helped show me new ways of morphing my hillslope hydrology interests into more coupled ecohydrology questions. Later collaborations on an NSF project in Mexico with Heidi Asbjornsen and Todd Dawson helped further my ecohydrolgical education. I’m still learning. But one thing I know for sure: I want to come back in my next life as a plant ecologist!
What do you see as an important emerging area of ecohydrology?
For me, the important emerging area of ecohydrology is still the one that was defined by Ignacio 20 years ago: the space-time links between climate, soil, and vegetation. And now, with the use of dual isotope tracing of these linkages over the past decade, so much new understanding has developed. But, many challenges and questions remain—and for a field-based person like me, these include: How to sample? Where to sample? When to sample? What to sample? There are extraction techniques now that affect our ability to link plant water with its source water. There are fractionation issues associated with transpiration that are throwing a monkey wrench into our mixing models. It will be interesting going forward, to explore how plant traits influence source apportionment; how plant water status drives water use decisions in the plant. All of this will be better understood with better combinations of isotope tracing matched with careful measurements of things like soil matric potential (using tensiometers) and sap flux (measured with internal heat sensors and dendrometer bands). Georg Ohm wasn’t an ecohydrologist, but his Ohm’s Law still appears to rule—and using it to guide new experiments on water source will be useful.
Do you have a favorite ecohydrology paper? Describe/explain.
There is no question that my absolute favorite ecohydrology paper is Hewlett and Hibbert (1967) “Factors affecting the response of small watersheds to precipitation in humid areas”. While perhaps not ecohydrology senso stricto, the paper laid out a manifesto for change in forest hydrology that endures to this day. It was a proceedings paper from the “First International Symposium on Forest Hydrology” at Penn State University. I love this paper so much I even wrote a tribute to it. One great quote from the Hewlett and Hibbert paper is: “usually a discussion of runoff from a watershed begins with the assumption that direct runoff is a product of overland flow and that other types of flow are mere exceptions to the general rule. Perhaps the opposite approach is more logical in the case of forest land; that is to begin with the assumption that all flow is subsurface flow unless there is evidence otherwise”. Wow. Powerful stuff. And great reading for any newcomer to the field of ecohydrology, hillslope hydrology, critical zone science or forest hydrology. I did not ever meet Hewlett. He retired a couple of years before I started my first academic positon. He is perhaps ecohydrology’s greatest unsung hero. I hope that one day we could push through a new AGU early career award in our section with his name on it.
What do you do for fun (apart from ecohydrology)?
I’ve been riding motorcycles since I was a child. When I was a PhD student, I rode a dirt bike around the Maimai watershed to my various sampling stations. I now ride to explore: new research sites, new nooks and crannies of Scotland following my annual Birmingham summer school shortcourse; scoping field sites on the Saskatchewan Prairie, and on my annual ~2,000 km ride between Saskatoon and Corvallis. Beyond motorcycles, I love to sail; beer can races on a nearby reservoir and adding bareboat charters onto conference and research trips in different sailing grounds. I love to ski in the winter and golf in the summer—with all these activities being better when done with my wife and now-adult kids. Lastly, I still bang away on the piano most days and one day imagine playing Elton John or Billy Joel songs in a piano bar; or perhaps more realistically, in an old folks home.