Context-dependent pattern and process: the distribution and competitive dynamics of an invasive grass, Brachypodium sylvaticum

Brachypodium sylvaticum, or false brome, a recent invader of North America, has spread rapidly following establishment in Oregon in 1939 and is now colonizing at least five US states. To understand how ecological processes and environmental context interact to facilitate invasion, we combined a GIS analysis of spatial patterns of invasion with a greenhouse competition experiment under two light and two nutrient levels, and a field competition-removal experiment. Brachypodium sylvaticum was concentrated along human-use corridors and in forests, where our experiments indicate it is a better competitor than co-occurring grasses. Forested areas near trails require the greatest focus for detection and control because the species' dual propensities to establish and thrive in these locations may make them key source areas for further invasion. Our methodology demonstrates how understanding both the patterns and processes of invasion enables the prescription of context-specific remedial actions.