Undergraduate Research

Sunniva Sheffield '23

OUR Featured Researcher: Sunniva Sheffield '25

Sunniva Sheffield
Photo Credits: Jacob Strauss

Sunniva Sheffield (she/her) is majoring in Chemistry, Biochemistry, and Environmental Studies. She is conducting mentored research under Professor John Petersen. Her project is titled “An Experiment Comparing Biochar Effects on Root, Shoot, and Fruit Production in Beans, Tomatoes, and Willows".

Please describe your project: 

Biochar is charcoal produced by the anaerobic combustion of biomass. When made from agricultural waste and applied to soils, it has the potential to both sequester carbon and increase soil fertility. Prior studies have documented a positive response of plants to biochar. However, the effects of biochar are variable across different biochar source materials, and soil types. This makes it challenging to generalize from previous research. Using a single source of biochar (hazelnut wood) and identical soil, we compared the effects of different levels of soil biochar on different plant tissues (root, shoot, and fruit) in three distinct species: cherry tomatoes, bush beans, and hybrid willow saplings.     

A brief summary (the elevator speech) of your research project:

Biochar is a special type of charcoal produced through the anaerobic combustion of biomass. Our research aimed to better understand how a single source of biochar might impact different tissues in distinct plant types, cherry tomatoes, green beans, and hybrid willows. We have documented significant increases in fruit, shoot, and root biomass with increases in soil biochar, with the highest biomass levels produced in the 26% treatment.

Why is your research important?

Today, biochar is advanced as a mechanism for sequestering carbon to address climate change while concurrently increasing soil fertility and thereby addressing the food needs of a growing population. In general, biochar is promoted for its capacity to: increase cation exchange capacity (CEC); increase base cation saturation, decrease bulk density, increase moisture retention, and increase pH which all improve plant growth. Biochar can be used in both agricultural settings to reduce the need to use fertilizers as well as a carbon sequestration method.    

What does the process of doing your research look like?

Throughout the summer and the fall I water the plants, measure their growth and do any maintenance. During the fall and winter I then start to process the plants through cutting their roots and shoots and measuring their dried weight, length, and running nutrient analysis on the soil and some of the leaf tissues. During the winter and fall I also do all of the data analysis using Rstudio and Excel and write!

What knowledge has your research contributed to your field?

We found a highly significant positive relationship between the amount of biochar added to the soil and plant biomass in all species but differences among species, with no significant difference in overall response between species. Tomatoes were the only species to exhibit significant differences in response in different plant tissues; fruit and shoot biomass increased significantly with biochar, root tissue did not. Bean germination increased significantly with biochar concentration. Date of first flowering was earlier with increasing soil biochar in beans but not in tomatoes. Control over both sources of biochar and soil composition in this experiment expands our understanding that biochar has different impacts on different plants and, in some cases, species-specific impacts on different plant tissues and other measures of fertility. Our results were contrary to research that found inhibiting effects of biochar at levels comparable to our 20% treatment. This study was conducted in a highly organic soil with hazelnut wood biochar; further research that controls for soil type and biochar source is necessary to determine the extent to which our findings apply for other biochar sources in other soil types and for other species of plants.

In what ways have you showcased your research?

Yale School of the Environment New Horizons Conference - 4/2022

Ecological Society of America and Canadian Society for Ecology and the Environment Annual Conference – 8/2022

Working on two papers now to submit for publication.

How did you get involved in research? What drove you to want to seek out research experiences in college?

I have always wanted to be a researcher; I always loved the lab sections of classes and so when I realized it was something I could do I started to contact professors on how I could get involved.

What is your favorite aspect of the research process?

I love seeing how my ideas or hypotheses change. I love watching a research idea blossom and turn into hours of work and analysis and real results. It is so cool when you see differences in your variables and the data proving what you thought or did not think would happen.

How has working with your mentor impacted the development of your research project? How has it impacted you as a researcher?     

I feel like I have become a more mature researcher who is able to figure out how to make a research project happen from scratch. John has allowed me to have the independence to work and decide things on my own while also always being a great mentor and providing support when I need it. A lot of things I had to figure out and learn on my own which has been super helpful. I feel prepared to take on grad school and other research projects after this.

How has the research you’ve conducted contributed to your professional or academic development?   

I really want to go into ecology and environmental science now as a career. Before I was not sure what I wanted to do after graduating, but now I feel excited and am applying to graduate schools to continue learning and researching in the field I am passionate and curious about.

What advice would you give to a younger student wanting to get involved in research in your field?      

Go into the professor’s office and ask questions about their research! Get to know them and make a connection. Show your interest and curiosity and ask how you could get involved.