The Lumberjack

Sand, wind and poop: a tale of American dune grass’ life troubles

HSU biology student Sean Thull tending an experimental planting of American dune grass in the HSU greenhouse. Photo and caption by Dr. Erik Jules.

For undergraduates Elizabeth Nguyen and Sean Thull, their past summer was spent staring at grass.

“We spent between two to four hours every three weeks, collecting data on Elymus mollis growth patterns at the Ma-l’el and Eel River foredunes,” Thull said.

Elymus, or American dune grass, is a native plant that can change the foredunes’ landscape.

Erik Jules, a professor in the Department of Biological Sciences, advised Elizabeth Nguyen, Sean Thull and Steven La Pointe on the project.

“Foredunes are dunes’ regions closest to the ocean. They often become eroded from crashing ocean waves or by wind,” Jules said. “U.S. Fish and Wildlife wants to keep foredunes from being eroded too fast and improve their resilience in the face of rising sea levels.”

Growing Elymus on foredunes is known to help the foredunes withstand heavy waves.

While Elymus growth at some of the region’s foredunes, such as Lanphere and Ma-le’l dunes, was healthy, Elymus grown at the Eel River foredunes suffered another fate.

“We wanted to know whether Elymus deaths were due to soil differences between these dunes and Lanphere dunes,” Thull said.

To answer this question, Nguyen, Thull and La Pointe observed the growth of Elymus from Lanphere dunes that were transplanted into Eel River and Ma-le’l soil.

HSU biology students Sean Thull (left) and Steven La Pointe collecting data on American dune grass growth at the Ma-le’l dunes. Photo and caption by Dr. Erik Jules.

A hundred Elymus were planted at each dune and an additional 41 plants were grown in the greenhouse.

“In the greenhouse, we cut the Elymus down to their base, giving them the same start point,” Thull said. “We watered them three times a week, rotated them to evenly distribute the sunlight and measured their longest leaf lengths.”

While the Elymus planted at Eel River had high mortality rates, the greenhouse Elymus grew strong. The longest leaf lengths in both soil types were not significantly different from each other.

“This showed that the soil at Ma-le’l and Eel River could supplement the plants just fine,” Thull said, “but something else in the environment is causing the plants to die.”

Unexpectedly, Elymus planted at Ma-le’l for this study also died.

“Because the Elymus in our experiment were planted at the same time that the winds at Ma-le’l was strong, this could have caused them to be buried by the sand and affected their growth,” Nguyen said.

“There were Elymus planted closer to the water, and planted when the winds were not as strong,” Thull said. “These plants were growing better comparing to our plants. If Elymus planting at Ma-le’l begins at the right season and Elymus is planted from the water inward, then maybe the plants could stabilize each other as they grow to alleviate the wind impacts.”

At the Eel River site, Nguyen and Thull found something different.

“We found rabbit scats in our Eel River’s Elymus plot,” Nguyen said. “Because there were lots of non-native, thick European beach grass near the plot, we think that the rabbits hide from predators in the beach grass, then come out to the Elymus plot to eat.”

A large patch of the invasive European beachgrass on the local dunes (left) adjacent to native dune mat vegetation (right). There is growing evidence that dense beachgrass patches harbor more rabbits, and that these rabbits then venture out to consume the native vegetation. Photo and caption by Dr. Erik Jules.

Nguyen and Thull’s observation made way for another project in Jules’ lab.

“Currently, I have a master student studying what rabbits eat out in the dunes and how that would impact the vegetation,” Jules said.

If rabbits are found to be the culprit of stunted Elymus’ growth, removing the invasive European beach grass from Eel River dunes could make them more prone to predators. This would cause the rabbit population at Eel River to decrease, giving Elymus a better chance to grow.

“Growing another plant species that could both restructure the dunes and deter the rabbits would be difficult,” Jules said. “Not many can tolerate the high salt soil of the dunes like Elymus.”

“Understanding how to help Elymus grow will usher in the growth of other native plants in the area, which could contribute to further dunes stabilization,” Nguyen said.

During this project, Thull and Nguyen gained the necessary skills to prepare them for a scientific career.

“We learned how to analyze our data with statistics and how to design an experiment based on what statistical methods should be employed,” Nguyen said.

“We’re also writing a report on this project,” Thull said, “and we’re learning that our experimental methodology are also used by professionals.”

Nguyen and Thull attributed their growth as researchers to Jules’ confidence in letting them work independently. This growth also transferred to their academic experience.

“We find the materials in our classes more exciting, because we see their applicability to our work,” Thull said. “This really makes us feel excited to eventually enter Ph.D programs.”