PhD student Jacob Weverka looks at carbon storage in Sedgwick’s grasslands
June 2024
Nikki Evans
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| Some of the answers to climate change lie beneath our feet. “Globally, soil is a major reservoir of carbon, which means that maintaining and increasing soil carbon is an important part of the fight against climate change,” says Jacob Weverka, a PhD student in the department of Ecology, Evolution, and Marine Biology at University California-Santa Barbara. Weverka has spent the last two years conducting fieldwork at Sedgwick Reserve. His research aims to understand how grazing affects soil organic carbon in different grassland communities. “In California and globally, grazing management is widespread,” he notes, “so finding management strategies that increase soil carbon on grazed lands could help sequester a lot of soil carbon.” We got together with Jacob to learn more about his research on grazing and soil carbon, the challenges and rewards of fieldwork, and what it’s like to be a graduate student in Ecology. Read on to learn more! 1. Would you provide us with an overview of your research at Sedgwick? There are many facets to this research, but this project in particular focuses on understanding how different grassland species modify grazing effects on soil carbon. Soil carbon stocks refer to the quantity of carbon contained in soil. Soil carbon ultimately originates from plants, so grazing could influence soil carbon stocks by changing plant growth. Specifically, I suspect that many plant species change their root growth after being grazed. Based on past experiments conducted in the lab and greenhouse, I suspect that species that need high quantities of nutrients and water maintain their root systems after grazing. Conversely, species that use nutrients and water more efficiently may decrease root growth or allow some of their roots to die after grazing. While we have observed this in individual plants growing in the greenhouse, my project at Sedgwick seeks to test this idea in more complex plant communities under field conditions. 2. How do you study this? We study this by simulating grazing in grassland plots. To simulate grazing, we simply clipped plants with scissors! We went into plots and clipped all plant material over 5cm high. We then measure the responses of roots and soil microbes. Microbes are responsible for cycling carbon in soil, so we measure microbial biomass and enzyme production to get a sense of how carbon cycling is changing in response to grazing.  Image 2: Jacob Weverka 3. Can you talk about the root observation windows you tested? The idea of the root observation windows was to be able to photograph roots growing in the soil in our plots, so that we could track root growth and death through time. To do this, I followed an open-source design to build “mini-rhizotron” plexiglass root observation tubes and tested this method in the field in 2023. While we were able to photograph some roots in the observation tubes in 2023, we found that our measurements of roots in these photos correlated poorly with measurements of root biomass from soil samples, so we have stopped using this method in 2024. View an example image captured by the root observation tubes here. |
 Image 3: Plexiglass tube inserted into the soil as part of a trial method used to image roots in a Sedgwick grassland |  Image 4: Undergraduate Researcher Assistant, Maiya Romero, uses a board to cross the creek after a wet winter |
| 4. Some readers may be wondering what it is like to do fieldwork. What do you like about fieldwork and what is something cool you’ve experienced in the field? I like that fieldwork is an opportunity to use simple observation to ask questions and form hypotheses. Grad school involves so much reading and desk work, but spending time in the field always leaves me with new ideas and questions. I’ve always appreciated that aspect of fieldwork, and another thing that has been fun with this project has been taking undergraduates into the field and talking about their questions and observations. So many cool things in the field! I spent many years as a field technician before I was a grad student so it’s hard to think of just one thing. But in this project at Sedgwick, one cool thing was after the heavy rains of 2023, there was a river bank that washed out to reveal the root system of a blue oak. It was cool to see its 20-foot taproot going all the way from the hillside to the creek, and gave me a new appreciation for those trees! 5. What is something you find challenging about fieldwork? When the weather doesn’t cooperate! We tried to set this project up during the winter of 22-23 when there was record rainfall. I thought I’d be able to drive to my site most of the time, but ended up having to hike 2 miles out to the site most visits because the road was too muddy. This was tough when I had to bring equipment out there. |
| 6. How did you get interested in studying ecology? And do you have any advice for young people hoping to launch a career in ecology or related sciences? I always thought biology was fascinating, and when I realized I could do it outdoors I was sold. Ecology is fun for me too because there are so many different sub-disciplines and ways of measuring the natural world, which I think leaves a lot of space for creative thinking by scientists. There are a ton of different ways to study ecology, but the most important skills are always your powers of observation and your ability to ask questions. I think a lot of great science starts by going outside, noticing a pattern in the natural world, and asking why that pattern exists. Thank you for sharing your research with us, Jacob!  Image 5: Undergraduate Researcher Assistant, Rayna Ruggeri, conducting lab work |