Robert Griffin-Nolan

Ecologist Robert Griffin-Nolan investigates how plants respond to climate change

When I was meeting with Prof. Robert Griffin-Nolan for our interview, congratulations were in order.

Recently, he received $1.5 million in funding from the University of California Office of the President’s Climate Action grant program as a co-principal investigator and he also was one of nine recipients of the 2024–25 Outstanding Faculty Awards at California State University, Chico.

At Cal State, Robert studies how plants respond to the challenges of a changing climate. He strives to understand what rising global temperatures and extreme weather events mean for plants, ecosystems and the planet more broadly. His research sheds light on how climate change could impact biodiversity and the health of natural landscapes.

However, Robert’s passion doesn’t stop at research. As a teacher, he is just as focused on helping students grow. For him, education is most powerful when it is engaging, inclusive, and driven by the students. That is why he strives to create a teaching environment where the students feel encouraged to ask questions to independently acquire their knowledge and succeed.

Please tell us a bit about your background. Where did you grow up?

I grew up in central New York in Syracuse and went to college in Ithaca, NY. I spent my summers camping with my family in Adirondack State Park, which many people do not realize is bigger than the five largest national parks combined. It is a massive and beautiful temperate forest.

When did you decide to make science your profession?

When I went to college I was interested in musical theater and science so I went to Ithaca, which had a good musical theater program but also was a liberal arts school where you could study science as well. I did a bit of musical theater there, and I really loved it in high school, but then I took a lot of science classes in the biology major. I originally thought it would be easier to get a job in science, but I also started really liking it once I was taking these classes, though I also thought about science journalism at one point. Acting has always been in the back of my mind and I suppose being a teacher is somewhat of a theatrical experience.

Which university path did you take to pursue your passion?

Ithaca College is a primarily undergraduate university, so much smaller than Chico. When I wanted to join a research lab my sophomore year, I was the only student working in the lab and I had a lot of one-on-one experience with the professor. This was a plant physiology lab, so that little decision I made then had huge ramifications for what I do now. I realized that I needed a lot of school to make this research my career, so I took a year off after undergrad and worked as a technician in a lab at Cornell and then joined the PhD program at Colorado State University.

I worked in a plant physiology lab because I did not want to work in animal biology labs where you had to kill animals. I kept doing plant physiology in my PhD but focusing more on climate change and looking at how you can use physiology as a tool to answer questions about how ecosystems might respond to climate change.

I had two postdocs after my PhD, including one at Syracuse University. My PhD was in ecology, but my first postdoc focused on molecular work extracting proteins. I would joke that I got through my PhD without ever having to touch a pipette. Then in my post doc I was extracting a ton of different proteins and doing a ton of molecular work to pair field-based gas exchange photosynthesis measurements of invasive plants with proteins that we extracted from leaf samples to see what proteins are involved in photosynthesis versus other processes in the plant. I was also able to go to Japan for field work before the pandemic.

My second postdoc was at Santa Clara University, which is in the Bay Area, but that was a remote postdoc. My wife was working at the National Science Foundation in Washington DC so we were living in DC and I was working remotely doing data analysis for a professor.

Did/Do you have a mentor who supports you?

My first mentor was Peter Melcher, the professor from my undergraduate studies. He is a super cool guy who taught me what I know about plant physiology and introduced me to the field, which I did not even know existed before that time. He brought me to conferences and I saw all these people presenting research which inspired me to do that as a career. I liked public speaking and talking about research was super fun.

I also had an amazing PhD advisor, Alan Knapp. He is a grassland ecologist studying how climate change, specifically drought and rainfall variability, impacts grassland ecosystem functioning. He was a super great mentor who really helped me scale up from physiology to ecosystem functioning. I believe a lot of science is storytelling and writing and he was really great at helping students figure out the story of their data without outright telling them the story. He is a great public speaker, writer and storyteller and just a really nice guy.

Both my postdoc advisors, Jason Fridley and Brody Sandel, were my statistics mentors. I call them the Stats Gurus in my life. They taught me a lot about code, much more than I learned during my PhD. I feel like your postdoc mentors are more like your colleagues because you are at a higher level than in graduate school – I still collaborate with them (and my PhD advisor) today.

Can you tell us about the research foci of your lab: the response of plants (physiology, biodiversity and ecosystem) to global change?

My research focus is diverse but in general I am interested in global change ecology, which is a broad field. Initially, “global warming” was the buzz term but that shifted to climate change as it became apparent that things other than temperature were changing, such as precipitation patterns and sea levels rising. But even that doesn’t capture the extent of human impacts. In addition to climate change, we’re seeing massive deforestation, habitat destruction, the spread of invasive species, and increased nutrient pollution from agricultural intensification fossil fuel burning. I am interested in understanding how those different changes impact ecosystems, mostly working in grasslands. I mostly research the impacts of drought but recently have expanded to other fields like biological invasions.

For my PhD, I was mostly interested in understanding how grasslands respond to drought and how they differ from one another. A grassland in New Mexico is not going to respond to drought the same way as a grassland in Kansas or Colorado. Part of those differences is climate. A drier grassland is already near a stressful level of water limitation which tends to make it more sensitive to drought. This may seem counterintuitive because those plants there are also adapted to the chronically dry conditions. My work was focused on physiology at the community level, so I looked at functional traits of all the different species there and then compile them in a community matrix of traits to see how the community traits shift with drought and how that impacts ecosystem processes like how much carbon is going into the system.

For my postdoc I was working a lot on the physiology and optimal nitrogen allocation of invasive plants. I was trying to figure out what makes them competitively superior to co-occurring native plants. Where are they putting nitrogen in their leaves that makes them a bit more aggressive photosynthetically than co-occurring native plants? Does that evolve when they are introduced or are they pre-adapted from where they came from because there are some traits in their native range that they maintained when they were introduced that make them invasive?

Currently at Chico we are focused on grassland restoration because much of the California grasslands are heavily invaded by non-native plants. We are trying to work with restoration practitioners and use our understanding of physiology of native plants to provide some advice and data on which species to utilize for drought resilient grassland restoration. I have a student working on drought survival, namely what makes certain species able to survive extreme droughts and what traits are related to that.

What methods does your team use to investigate the plants’ response?

We use observational and experimental methods both in the field and in the greenhouse. For example, to study drought in a greenhouse you just water pots less. Out in the field we built this experimental infrastructure called “rain out shelters” which are basically clear roofs that have panels which allow some rainfall to come in but block a certain percentage based on the intensity of the drought. We also hydrologically isolate the soil by digging a trench and putting plastic under there. We make this fairly large hydrologically isolated plot, and we can impose an extreme drought event for multiple years. Other times I have done experiments where we have a water tank nearby and we can manipulate the rainfall and change the pattern. We can make the rainfall less frequent but with larger rainfall events, which is one expectation with climate change. Then we can assess ecosystem scale processes of how these ecosystems and biodiversity respond to those experiments.

On the physiological scale the bread and butter of our lab is a device from LICOR called an infrared gas analyzer where you essentially clamp it onto a leaf and measure the amount of CO2 a leaf is absorbing via photosynthesis. Similarly, you can do the same thing with water vapor and know how much water vapor is coming out of the plant and can measure transpiration. With this you can see how photosynthesis responds to drought or nutrient deficiency or changes in CO2 concentration or water vapor.

We have another tool that is useful for understanding water stress called a pressure chamber where you clip leaves from a plant and put them inside this pressurized chamber, and it squeezes them until water comes out of the stem. It is essentially equal to the negative pressure that plants are under. If you need to apply more pressure to get the water out, it means that the plants are under more extreme negative tension pressure. It is really a measure of plant water status or water stress. I also did some molecular work of extracting proteins for my postdoc. That is not something I do currently, but I would like to get back into it.

In terms of permits to do these field studies, the trenching is the big part because it can be a bit destructive. The Big Chico Creek Ecological Reserve is a research facility nearby where I am interested in setting up drought shelters. However, I will work with the Mechoopda tribe first to see if they are comfortable with me digging these trenches, given a lot of local meadows and grasslands up there have the potential to be burial sites. Many of the ecosystems I have worked at in the past have been at sites that are part of the long-term ecological research network. There is a big network of NSF funded sites, and they are very interested in setting up experimental infrastructure to manipulate the ecosystems. Soon I will be shifting to work more on rangelands, in which case I need to work with land managers that have cattle and are interested in the research but do not necessarily want me to dig up their whole land.

Is there a general response pattern or do you see vastly different responses depending on the plant species and their ecological niche?

The answer for most questions in ecology usually starts with: “it depends”. For example, with CO2 if you were to increase CO2 concentration inside the leaf, a C4 plant like corn or wheat would not respond much because C4 photosynthesis, which is a carbon concentrating mechanism of photosynthesis, is fully efficient at using the normal amount of CO2 it receives in our atmosphere. Most other plants are C3 plants. They have this issue of photorespiration where the enzyme involved with photosynthesis, rubisco, interacts with oxygen and does this different process that then reduces the photosynthetic rate of plants. If you increase the CO2 concentration, rubisco is more likely based on enzyme kinetics to bump into CO2 rather than oxygen.

One general trend that I have been working on recently for writing up a post doc paper is optimal nitrogen partitioning. We looked at where plants are putting nitrogen in their leaves. We studied dozens of different invasive plants and co-occurring native plants and looked at them in shade environments, like an understory forest, and then in open environments and then compared their photosynthetic rate with that LICOR instrument and then looked at the proteins in their leaves. We found that invaders of understory shady habitats invest more nitrogen in their invaded ranges into light harvesting because that is limiting there and would make them do better. Invaders of open habitats where light is not limiting do not invest more in light harvesting, things like chlorophyll. They invest more in rubisco, so when they invade a new place compared to their home range, they invest more in rubisco and have a higher photosynthetic rate because they can acquire more CO2 compared to natives.

In grassland work there is a general trend of wetter grassland being less sensitive than drier grasslands to drought. The work for my PhD was showing that community functional composition is somewhat related to that sensitivity where functional diversity, a diversity of attributes within the community of species with different traits, yields resistance to droughts, like genetic diversity yielding immunity from diseases in a population. California grasslands are particularly interesting because they are in a Mediterranean climate, so the plants often go dormant during the summer months and wait until the spring rain returns.

Do you have career highlight(s) you like to look back upon?

I feel like I am still in my early career, but one highlight recently is when I took three students to the Ecological Society of America conference last August. It was super fun because that is how I got into science, when Professor Melcher took me to a conference. Two were undergraduate students who had never been to a conference. It was cool to introduce them to my colleagues from Colorado and elsewhere and just introduce them to the field of science communication and science conferences, which can be overwhelming but also a great networking opportunity. One of them ended up getting into a fully funded master’s program at California State Polytechnic University, Humboldt based on meeting a colleague of mine at that conference.

Can you share a future research and teaching goal of yours?

I have a lot of different research goals. I am really interested at Chico in trying to figure out how to make my research and teaching programs a bit more joined. Right now, I feel like I teach and then I have my research. I want to make it so that students in my plant physiology class are collecting data for a long-term project that I potentially want to publish. It is hard to do that because a lot of the research we do uses these expensive tools which we do not have in a quantity that you can give one to every student in the class to use. I am trying to shift my plant physiology lab in the next couple of years away from certain labs where I do not think they are gaining skills that they would necessarily use in a career in physiology. It would be cool to teach them the tools that I use as a plant physiologist and then have them develop a research project, whether it works out or not, and then say on their resume that they used these tools that physiologists working for the USDA use, for example.

Who, what, when, where & why?

Who?

- would you like to conduct research with if you had the chance?

I’d like to work with Tim Brodribb, someone I’ve never met but I’ve enjoyed reading his work. He is famous in my field and at the University of Tasmania. He seems like a really cool guy. He studies Xylem cavitation, which is when these bubbles of air block vessels in Xylem, but he developed this cheap tool or method to visualize it with very simple light microscopy. You can clamp it onto a leaf and watch it happen in real time as these bubbles of gas spread through plants. Only recently have we been able to measure this important process in real time and visualize it.

What?

- do you like to do in your free time?

I like to spend time in nature, preferably away from cell service, with my wife.

When?

- do you find inspiration for your research?

I would say I find inspiration when I am reading, which is hard sometimes as a professor to find time for because there are other things that just seem more pressing in the moment. Whenever I get the chance to just read a paper fully or read several abstracts or peer reviews of paper, that is when I think of new ideas. They are not just going to pop into my head. Reading is when I get those detailed ideas where I think the researchers did something really smart and inspires me to tweak their idea slightly or test it out on a different species.

Where?

- is your favorite travel destination?

My favorite destination was Japan during my postdoc but increasingly I have been wanting to travel for fun. Italy has a soft spot for me because that is where my wife and I did our honeymoon. We spent several weeks in northern Italy.

Why?

- did you choose your specific research topic(s)?

I was really interested in ecology because of my upbringing going camping a lot as a kid and I wanted to do something outdoors. I was not sure if I wanted to work with plants or animals as an undergraduate because I was interested in a lot of things and I kind of fell into it. I knew I did not want to do something like killing Guinea pigs, which was part of the neurobiology major, so I joined this plant physiology lab, and I was going to do just one rotation there and then check out some other labs. Then I got to use that instrument where you clamp leaves on and thought it was cool. For graduate school I wanted to still do that, but I wanted to apply it to climate change, which I obviously found very concerning but also thought was very interesting.

…or?

Attend a party or be the host?

Be a host.

Museum or movie theatre?

Depends on the museum, but probably a museum. I like watching movies at home.

Sneakers or dress shoes?

Sneakers.

Optimist or pessimist?

Optimist but probably depends on the scenario we are talking about.

Ambition or comfort?

I feel like saying comfort but probably my family would say I am ambitious.

See the future or change the past?

Probably change the past for specific things. Seeing the future, you are just observing it but then it could be very depressing, and you have to watch it happen.

The interview was conducted by Nicole Kilian and has been edited and condensed for clarity.

Image sources: Robert Griffin-Nolan.

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