An investigation into the presence of slender false brome (Brachypodium sylvaticum) and its relationship with plant communities in New York State

Abstract

Globalization has led to an increased frequency of biological introductions. These introductions have the potential to progress into invasions that negatively impact the recipient communities. However, not all species may have large impacts on native species or community assembly patterns. By understanding where invaders are likely to establish and their impacts, we can better allocate resources for early detection and rapid response to prevent future invasion. Brachypodium sylvaticum is an invasive grass in North America that is native to Eurasia and North Africa. First introduced in the Pacific Northwest, it has since made its way to the East Coast and western New York. As a relatively new invader, little is known about its environmental preferences, potential impact on communities, and its competitive ability. My study investigated these questions. In the first portion of my study I conducted vegetation surveys and environmental measurements in eight invaded and three uninvaded communities that varied in B. sylvaticum population size, environmental conditions, and forest types. As predicted, I found that water content and canopy cover determined B. sylvaticum abundance. It preferred drier soils within wetter sites, and wetter soil within drier sites. Contrary to my expectations, I found that B. sylvaticum abundance was not dependent on canopy type. Brachypodium is associated with lower species richness, which provides evidence that the invader is negatively impacting communities. However, impacts on recipient communities are limited to changes in richness as I did not find significant difference in community structure or assembly patterns between invaded and uninvaded quadrats. In the second portion of my study, I conducted a greenhouse competition experiment in which I selected species from my co-occurrence analyses to grow in competition with B. sylvaticum. I found that B. sylvaticum is not a strong competitor against another exotic grass Combined, my studies indicate that B. sylvaticum may not be a strong competitor on the east coast and may instead be a passenger of already degraded communities.