The invasive annual grass Ventenata dubia is insensitive to experimental removal of above-ground resident biomass across a productivity gradient

The success of introduced plant species is influenced by interactions with the resident community, and these interactions can vary in strength and direction depending on environmental context. Understanding how interacting biotic and abiotic factors influence invasion is critical to managing invasions and assessing invasion susceptibility across multiple ecosystems, especially for recently introduced species in beginning stages of invasion where early detection, eradication, and prevention are critical for effective control. Here we use an in-situ biomass removal and seed addition experiment to investigate how resident species influence invasion success by a rapidly spreading invasive annual grass, ventenata (Ventenata dubia) across a productivity gradient composed of three distinct vegetation types in central Oregon, U.S.A. In contrast to our predictions, the removal of residents did not have a clear effect on ventenata success, and the effect did not vary by vegetation type. Instead, our results suggest that the ventenata invasion is more strongly driven by dispersal limitations and microsite condition than species interactions. These findings have important implications for managing invasions in non-forest ecosystems where common management actions such as prescribed burning, grazing, and planting native species involve the alteration of above-ground biomass, and for expanding invasion frameworks to aid the management of future invasive species.

Automated summary

The success of ventenata invasion is more strongly influenced by environmental and dispersal limitations than by interactions with resident species. These findings have important implications for managing invasive species in non-forest ecosystems.