Herbicide Effects on Soil Seed Banks

Title: Herbicide effects on soil seed banks Co-authors: Blake Roeslein, Abby McMurtry, Bryan Endress, Akasha Faist Invasive annual grasses are a major driver of grassland degradation globally. In perennial grasslands, invasion can heavily impact biodiversity including potential changes to the soil seed banks. Seed banks, the living seeds stored in the upper soil column, play an important role in healthy systems. To reduce negative invasion outcomes, whether in the seed bank or aboveground vegetation, pre-emergent herbicides are a commonly used tool for land managers. Pre-emergent herbicides work by targeting seeds as they emerge from the soil. Our study asks what effects pre-emergent herbicide have on the seed bank of both target and non-target species. For this study we used two herbicide combinations: 1) Rejuvra and 2) Rejuvra and Plateau together. Rejuvra is a cellulose inhibitor that targets annual grasses for up to four years after application. Plateau is an acetolactate synthesis inhibitor that targets perennial and annual grasses and broadleaf plants. We had three replicated treatments applied to four field sites in northeastern Oregon. Our first treatment was a control without herbicide, the second Rejuvra, and the third Rejuvra with Plateau. Approximately one month after herbicide application we collected representative soil seed bank samples across the sites and treatments. After collecting, soils were cold treated then planted in a greenhouse to assess how the herbicide treatments effect plant functional type germination and death. This study will see whether our herbicide treatments impact the seed bank and are effective at annual invasive grass control, and/or if they have effects non-targeted species.