Mycorrhizal Associations and Seedling Recruitment

There has been some evidence that has shown that seedling recruitment is affected by the mycorrhizal network at the site of germination, altering survival rates and growth rates. Mycorrhizal associations are a symbiotic relationship between plants and fungi, which is critical to a plants growth. In return for carbohydrates from the plant, the fungal hyphae attaches to the plants' roots, extending their reach thus increasing nutrient uptake. We focused on the most common types of myccorhizzal associations, ectomycorrhizae (ECM) and arbuscular mycorrhiza (AM). Variation in nutrient mining of ECM and AM fungi creates variation in soil chemistry and therefore the potential to affect seedling recruitment and survival. We tested this by sampling 22 different plots and we identified more than 20,000 seedlings and nearly 1000 trees.

In the summer of 2019, myself, undergraduate Rachel Wichterman and PBIO MSc student Taylor Sparbanie, worked in Waterloo Nature Preserve about 15 minutes west of Athens. The plots established at Waterloo were laid out by Dr. Jared Deforest for his research on soil chemistry and how soil chemistry affects on forest ecosystem function. We were looking at seedling establishment in the control plots and the lime plots. The lime treatment raised the pH of the soil creating a more basic soil.

At each plot we first created a 10m radius circle and then we identified and measured diameter at breast height (DBH) of each tree within the radius to determine basal area. Since trees associate with either AM or ECM fungi depending on the genera of the tree, we were able to calculate the percentage AM basal area in each sample based on the species.

After identifying the trees we then turned our attention to the saplings to test the response of seedling recruitment. We laid out flagging tape to break the large circle into slices to make sampling easier and decrease the amount of seedlings missed and double counting. Each seedling was classified into three stages; Stage A(germinated this year), Stage B(Older than a year, but less than 6), and Stage C(older than 6 years). With various stages, I hope to test the differences in survival rate of seedlings under differing mycorrhizal networks.

Before this project I did not have any experience in R-Studio, but with the help of my research advisor Dr. Rebecca Snell (PBIO) and her R-statistics course, I have been working hard on improving my ability to read and write code. Data analysis may be slow but I'm learning a lot along the way and I'm very excited to keep learning more. I also had very little experience in tree identification but after spending a lot of time actively learning in the field and staring at field guides I was able to quickly identify dozens of woody species.

This project has taught me organization skills, identification skills, and patience. I learned that there will be mistakes and mishaps along the way so it's important to be able to adapt and work out ways to avoid making the same mistake again. I'm very grateful for being able to work, research, and learn in such a great environment and I'm excited to continue my project and see what else I will learn!