Google Scholar: https://scholar.google.com/citations?user=JQOZ4cUAAAAJ&hl=en&oi=ao
As almost everyone else in this series has noted, ecohydrology is about the intersection and interactions between ecology and hydrology. However, being affiliated with a watershed management group at the time that we were preparing to launch the journal Ecohydrology, I was challenged to defend how this really differed from watershed management, which had for decades considered both ecology and hydrology. I think there are three criteria that, if not distinct from watershed management, represent areas of focus that have historically not been considered in depth by it. First, historic use of the water balance equation usually results in aggregation of evaporation from plant foliage, evaporation from soil and transpiration from plants, yet these together dominate the water budget and need to be disaggregated to better understand and manage ecosystems and watersheds. Developments in flux towers and stable isotopes over the past couple of decades have changed the game in addressing these areas. Second, feedbacks are really critical, whether they relate to runoff redistribution, to vegetation cover modifying soil evaporation, or broad-scale vegetation change impacting local and distant climate. These were previously challenging to evaluate, and to some degree remain so, but are readily modeled such that different aspects of the predictions can now be evaluated. We emphasized these feedbacks when we defined the scope of the journal Ecohydrology. And third, as highlighted by Rodríguez-Iturbe in his classic 2000 paper, soil moisture is a key integrator, which contrasts with the primary focus of watershed management on overland flow, streamflow and groundwater recharge. The three criteria listed are critical ones to study if we are to effectively address the challenges associated with rapid change in climate and land use.
What are your undergraduate and graduate degrees in?
I first got interested in ecology looking at illustrated diagrams of food webs and energy flow in high school, so then went to New Mexico State University to get a B.S. in Agriculture through the Wildlife Science program, moving more from organisms to ecosystems as I progressed. After a couple of summers of University of Georgia's Savannah River Ecology Laboratory, I decided to go to graduate school at Colorado State University, where I could simultaneously study how to use radiotracers in the environment and work on applied problems related to contaminants, working with Ward Whicker—an international leader in radioecology. I worked on modeling how contaminants released during 1960s weapons testing were transported through agroecosystems for my M.S. I wanted a more ecological focus for my PhD and Colorado State also had a broad Program in Ecological Studies that I completed. I had the opportunity to go back to Los Alamos, NM, where I grew up, to work at Los Alamos National Lab (then run by University of California) on water balance issues in a semiarid piñon-juniper woodland as a way to consider longer-term issues that might influence adjacent landfill covers that would likely go through succession to also become woodlands. I learned a great lesson when committee member Bill Lauenroth challenged me in my oral exam to explain why shortgrass steppe around Fort Collins and semiarid woodland around Los Alamos both had the same precipitation but different vegetation—an exam question I fell flat on (short answer: precipitation event size distribution is related to soil moisture depth distribution, which is related to plant life form). I spent the next three months mostly reading and that really reframed my thinking about semiarid ecosystems.
How did you arrive at working in/thinking about ecohydrology?
So, while working on issues of water balance in these semiarid woodlands, and collaborating with Brad Wilcox on runoff redistribution (among other topics), Brad came running down to my office to talk about the 2000 Rodríguez-Iturbe paper in Water Resources Research that so many others in this series have mentioned. He, Brent Newman and Osvaldo Sala then went on to co-organize the first Chapman Conference in ecohydrology, which I helped with. I was still worried about becoming established as an ecologist so had some reservation about becoming too affiliated with something that ended in "hydrology", as I shared in this essay. Nonetheless, it served as a great framework for thinking about how semiarid systems worked. During that time, I was fortunate to have Ecohydrology Leaves founder Shirley Papuga as an undergraduate research student to work with. Additionally, colleague Craig Allen of Bandelier National Monument shared his research insights and invited me to work with him on drought-related tree mortality, and I have been working on that ever since, recently highlighted here. At first I did not really associate tree mortality with being an ecohydrological problem, but it in fact largely is. And tree die-off is becoming so extensive—for example recent California tree mortality approaches 150 million trees—that I am now working with a team that includes Abby Swann of University of Washington, who leads the modeling, on "ecoclimate teleconnections", where we estimate how the effects of complete tree loss in one region affect climate and vegetation (including crops) in others.
What do you see as an important emerging area of ecohydrology?
The most fundamental challenge we have as a society is to make rapid reductions in emissions fast enough to try to hit the goals spelled out in the IPCC Special Report on 1.5oC. Both ecohydrology and my particular focus on drought- and heat-related tree die-off are deeply intertwined with this issue. Most countries include afforestation (adding trees) as a major part of their plan for addressing goals of the Paris Accord. Ongoing widespread woody plant encroachment, as studied by Steve Archer, also contributes to terrestrial carbon gains. But at the same time, extensive deforestation must be dramatically reduced. And the most complicated aspects of the challenge are twofold. First, we are counting on increased tree biomass to slow the warming, but while we are warming, the probability of wildfire and of tree die-off (directly from drought or in association with pests and pathogens) are both increasing rapidly. Tree sensitivity to heat waves may make this situation even worse. Second, our research on ecoclimate teleconnections is suggesting extensive tree loss in one region can alter the plant productivity elsewhere in the same country or in another one, in some cases increasing it and in some cases decreasing it. This has profound implications for us as we attempt globally coordinated carbon management. Understanding ecohydrological processes and feedbacks are key to helping us address the greatest challenge of our time and one of humanity's greatest challenges ever.
Do you have a favorite ecohydrology paper? Describe/explain.
This is such a hard question, because there are so many great ones out there. I think the single best example of ecohydrology is the small, often overlooked, 1996 book by Ludwig, Tongway and others, "Landscape Ecology, Function and Management: Principles from Australia's Rangelands", because it does it all: develops a conceptual framework that is explicit and clear in terms of ecohydrological feedbacks, and then goes on to support it, model it, and provide monitoring and management guidance.
What do you do for fun (apart from ecohydrology)?
I enjoy spending time with my family, including my adult sons and their girlfriends; listening to rock, jazz and some classical on vinyl records on a great stereo at home; going to concerts; watching University of Arizona basketball, visiting the rocky Oregon coast; reading novels and poetry; and traveling.