An Interview with Benton Taylor, Assistant Professor of Organismic and Evolutionary Biology and Faculty Fellow of the Arnold Arboretum

This fall, we welcome Benton Taylor as a new assistant professor of organismic and evolutionary biology at Harvard University and Faculty Fellow of the Arnold Arboretum. Ben’s research focuses on how plants respond-to and influence their environments, particularly in view of climate change. While the Taylor Lab primarily focuses on plants at the ecosystem scale, his investigations also require viewing plants at individual and community scales to gain a better understanding of the role that plants play in global processes. We talked to Ben to learn more about his background in science, his focus on nitrogen-fixing plants and their ecology, and how his studies may soon involve visits to active volcanoes.

Ben Taylor at La Selva Biological Station in Costa Rica
Ben Taylor pauses during field work sampling the roots and nodules of nitrogen-fixing trees at La Selva Biological Station in Costa Rica. Marc Campos

How did you become interested in studying plants and how plant communities are responding to climate change?

After my master’s, I took a job as an assistant in a lab at the College of Charleston working on experiments to simulate the effects of elevated carbon dioxide (CO2) levels on forests. In particular, this research looked at root dynamics and understanding how trees get more nitrogen to fuel their responses to increasing CO2. So my curiosity moved from high on the food chain—bears—to the basement of the trophic pyramid, the nutrients that plants take up from the soil. Just as learning how plants dictate animal life had driven me to study plants, the realization that nutrients control plant life led me to ecosystem ecology and biogeochemistry. If you really want to understand how the world works, understanding carbon, nitrogen, and
phosphorus cycling really lie at the core of those questions.

My interest in biology started as a kid in rural Tennessee, where I spent a lot of time in the woods. Growing up in those surroundings, I developed a strong love for nature and desire to understand it—along with a strong allergic reaction to poison ivy! But even that couldn’t keep me out of the forest. Originally I wanted to study the bears at Smoky Mountains National Park, but as I went through school and began graduate studies, this interest honed down to the study of plant and animal interactions. So while conceptually I was working with animals, I soon realized that plants really run the world! Animals live or die based on what happens with plants, so that was a turning point in favor of botany.

If you really want to understand how the world works, understanding carbon, nitrogen, and phosphorus cycling really lie at the core of those questions.

Ben Taylor

At this point I tend to think of myself as a tropical ecologist. I certainly do projects in the temperate zone and I plan on doing more now that I’m at the Arboretum, but most of my work takes place in the tropical forests of Central and South America. These forests have a huge impact on the global carbon cycle, so they are a perfect place to study the interactions between forests and climate change.

What interests you about tropical forests, and how do they support your research aims?

The only way to describe a tropical forest is biology on steroids. The incredible levels of diversity, productivity, and plant growth create constant, intense biotic interactions that are almost overwhelming. It just gets you really excited about biology in general, and that got me hooked on tropical forests.

I think the basic, fundamental differences in tropical and temperate forests shaped, pretty dramatically, both where I tend to work and the questions that interest me. And certainly, my “scientific” love for tropical forests is related to the outsized effect their productivity has on global carbon, nutrient, and water cycles. They have a much larger impact on these global systems than the amount of area that they comprise. Old growth forests in New England are effectually non-existent, and that’s true pretty much across the East Coast. So I feel like one of the main things that excites me about work in tropical forests is that there is still enough that is untouched and that we can still work to preserve.

Your work in tropical forests largely considers the availability and role of nitrogen. What are nitrogen-fixing plants, and how do they function in an ecosystem?

Nitrogen fixers include the legume family (Fabaceae) with taxa such as clover, soybeans, alfalfa, lupins, and peanuts. Bacteria living inside the nodules on their roots convert atmospheric nitrogen—which is effectively limitless—into biologically-available nitrogen that the plants can use. When the tree drops its leaves, that usable nitrogen goes into the soil, gets churned up by microbes, and can be taken up my neighboring plants. This suggests that nitrogen fixers should be good for the growth of a forest. In fact, nitrogen fixers tend to come early into a disturbed site, and they are associated with the rapid regrowth of forests after clear cutting.

With this in mind, you would expect that trees near nitrogen fixers should grow more rapidly than those that are not near nitrogen fixers, and that a forest that has a lot of nitrogen fixers should grow relatively quickly. But actually we don’t find that to be true, and in the plots where I work in Costa Rica, they actually had a negative effect on forest growth. So we’re breaking down this notion that nitrogen fixers are superchargers for an ecosystem. And to be honest, it doesn’t line up with our understanding of Darwinian natural selection that a tree would fix all this extra nitrogen to help competing trees that might overtop it.

Ben Taylor weighs soils for nutrient analysis in the field
Ben weighing soils for nutrient analyses in a makeshift biogeochemistry lab in the rainforest understory. Ben Scott

What are the some of the projects related to this area of interest that you are currently pursuing?

Much of my research focuses on what is controlling how much nitrogen these plants fix and the effect their nitrogen cycling has on the surrounding forest. What controls nitrogen fixation is really critical, because it’s the primary input of nitrogen into a forest ecosystem. Intuition suggests that nitrogen fixers should have a strong competitive advantage when soil nitrogen is scarce (because nitrogen fixers can supplement their nitrogen needs by fixing nitrogen from the atmosphere). Yet, nitrogen fixers often don’t appear to have the strong competitive advantage in nitrogen-limited habitats that we think they should, and they often don’t end up relieving nitrogen limitation for other plants in forests. So something must be driving the process besides the scarcity of nitrogen in the soil, and that could be light availability, water availability, or any number of different things. Understanding those factors is an important piece of my work. And the effects that nitrogen fixers have on the forests they inhabit represents the flip side to their ecological relationship, which I also find fascinating.

Much of my research focuses on what is controlling how much nitrogen these plants fix and the effect their nitrogen cycling has on the surrounding forest. What controls nitrogen fixation is really critical, because it’s the primary input of nitrogen into a forest ecosystem.

Ben Taylor

Another chunk of my work is very closely related but looks at how forests respond to carbon dioxide. At present there is a huge push in climate change research to try to understand how forests are going to react to an atmosphere that is at five or six hundred parts per million carbon dioxide (currently we stand at nearly 410 parts per million). Since plants photosynthesize using CO2, we expect that forests will grow larger as CO2 in the atmosphere increases—what we call the CO2 fertilization effect. Unfortunately, we think there may be a ceiling on that effect due to limits on soil resources, primarily nitrogen which plays an essential role in photosynthesis. So a lot of my work is looking at how forests respond to extra CO2 and how they change their root strategies or their symbiotic strategies underground to get more of the nitrogen they need to grow.

You recently received a Star-Friedman Research Grant at Harvard. Could you describe the work that this award will fund?

Much of the research into the long-term effect of elevated carbon levels on forests has been conducted in the temperate zone where CO2 fumigation experiments allow us to simulate conditions predicted 100 years from now. Those experiments are logistically impossible in tropical forests. The Star-Friedman Grant will fund a project I’m working on with collaborators at NASA’s Jet Propulsion Lab to study environments around active volcanoes in Costa Rica. Cracks in the bedrock around these volcanos release high levels of carbon dioxide naturally into the surrounding forest. So the grant will allow us to develop these volcanic sites as natural CO2 enrichment experiments, where we can look at these forests that have been exposed to extra carbon dioxide for hundreds of years, and do so in the tropics where the effects could be much more dramatic and consequential.