PS 39-8 - Investigating the effects of invasion and restoration on European beachgrass (Ammophila arenaria) decomposition through field experiments and structural equation modeling

Wednesday, August 17, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

SF

Savannah Fuqua

PhD Student
University of Arizona, United States

Coauthor(s)

LP

Lorraine S. Parsons

National Park Service, United States
BY

Ben Yang

University of Arizona, United States
AB

Albert Barberan

University of Arizona, United States

Background/Question/Methods

Understanding whether changes in community composition following environmental perturbations result in changes to community function is a major challenge in ecology. There is increasing evidence that invasive plants alter the soil community in their invaded range. However, the consequences of these changes for soil community functions such as litter decomposition are not well known. Additionally, the methods used to remove invasive species, such as treatment with herbicide, also have the potential to alter soil communities and thus may affect their function. At Point Reyes National Seashore (PRNS), previous work has demonstrated that invasion by European beachgrass (Ammophila arenaria) as well as herbicide treatment leads to changes in the relative abundance of key decomposing microbes. We conducted a litterbag experiment to test if rates of Ammophila arenaria decomposition varied across uninvaded, invaded, and herbicide treated habitats. We placed nylon bags of varying mesh sizes containing naturally senesced or herbicide-treated Ammophila in each habitat type and measured changes in mass at 3, 8, and 13 months. At the 13 month time point, we collected microbial community samples for amplicon sequencing. Additionally, we used structural equation modeling to test explicitly whether changes in community composition and changes in function were causally linked.

Results/Conclusions

We found evidence that decomposition rates differ between invaded, uninvaded, and restored habitats. Overall, invaded sites showed higher rates of decomposition than uninvaded or restored habitats, but differences in rates diminished over time. Herbicide treated Ammophila showed higher rates of decomposition than naturally senesced, but only in bags with 1mm mesh. 60 micron mesh excludes almost all organisms aside from microbes, whereas 1mm mesh allows entry by microbes as well as some soil mesofauna. Further work is needed to determine the relative importance of these groups for soil function at PRNS. We combined the results of our decomposition study with our data on microbial community composition and extracellular enzyme activity to create structural equation models. Specifically, we tested how changes to both the aboveground plant community and belowground microbial community following invasion and restoration contributed to altered rates of carbon hydrolyzing enzyme activity and rates of decomposition. Understanding whether these changes result in reduced decomposition at PRNS is vitally important, as dead beachgrass persists on the landscape for years, continuing to suppress native growth. More broadly, our study advances our understanding of the relationship between community composition and important community functions.