Understanding the biology, ecology, and integrated managment of Ventenata dubia

Abstract

Ventenata dubia (Leers) Coss., common name ventenata or African wire grass, is a non-native winter annual grass of increasing concern in western Montana. In North American, V. dubia appeared in the early 1950s; since then it has successfully established in the northeastern and northwestern United States. It is known to invade areas previously inhabited by Bromus tectorum (cheatgrass) and Taeniatherum caput-medusae (medusahead). In the Intermountain Pacific Northwest, V. dubia has caused substantial ecological and economic impacts in perennial grass habitats. Varying disturbance regimes contribute to its rapid expansion over the last decade. Impending climate change threats have the potential to exacerbate the spread of this invasive species. Three independent studies were conducted to explore the biology, ecology, and integrated management of V. dubia populations in Montana to alleviate impacts by this species and other invasive annual grasses. A growth chamber study tested the effects of elevated carbon dioxide and temperature on seedling growth of V. dubia in response to climate change and in competition with B. tectorum. This competition replacement study indicated that at elevated climate conditions V. dubia and B. tectorum grow smaller and competition with V.dubia has the potential to decrease B. tectorum growth. A field-based herbicide efficacy trial utilizing the active ingredient indaziflam compared it to other commonly used herbicides to determine long-term control of V. dubia and potential plant community changes at 8, 11, 20, and 23 months after treatment. Foliar cover, species richness, and functional group biomass were collected. Findings indicated indaziflam can control V. dubia up to three years with positive implications for plant community dynamics. A revegetation study was used to determine the optimum seeding time for perennial grass species, Pseudoroegneria spicata, and the effects seeding time can have with competition dynamics with B. tectorum. A randomized complete block design was established and P. spicata grown for one season prior to Bromus tectorum seeding. After the second growing season, tillers and biomass were collected for both species. Findings indicated priority effects can occur with fall and early spring seeding of P. spicata, with implications for suppression of B. tectorum at earlier seeding dates.