Consequences of Ventenata dubia 30 years postinvasion to bunchgrass communities in the Pacific Northwest

Abstract

Ventenata dubia (Leers) Coss., an invasive winter annual grass, negatively impacts grassland community composition and function in the Pacific Northwest. Ventenata dubia established in Palouse prairie and canyon grasslands of northern Idaho/eastern Washington in the mid-1980s to early 1990s. Understanding and comparing patterns of invasion can elucidate future trends as its range expands. We performed surveys in Palouse prairie (2012 and 2013) and canyon grasslands (2018) to assess V. dubia abundance. Specifically, we correlated species richness, Shannon diversity, rank abundance, and indicator species with no, low (<12.5%), and high (>12.5%) V. dubia cover. We used non-metric multidimensional scaling analysis (NMDS) to visualize species similarities and associations with abiotic variables. In both ecoregions, V. dubia was very common, appearing in nearly 60% of 450 plots. When present, V. dubia cover averaged 26% (± 2.3 SE) in Palouse prairie and 19% (± 1.8 SE) in canyon grasslands. Indigenous plant species richness and diversity were lowest in plots with high V. dubia cover. In canyon grasslands this relationship held for nonindigenous species; in Palouse prairie, nonindigenous plant richness and diversity were higher with high V. dubia cover. Ventenata dubia and other winter annual grasses [Bromus spp., Taeniatherum caput-medusae (L.) Nevski] were moderately associated according to the NMDS analysis. Indicator species analysis showed V. dubia was positively associated with nonindigenous winter annual grasses and negatively associated with indigenous low shrub species. Abiotic factors that explained V. dubia abundance included shallow soils and a south to west aspect. Overall, these findings indicate V. dubia can successfully invade both dry and relatively wet plant communities and is more abundant than other invasive annual grasses. We suggest these findings foreshadow what will happen in sagebrush steppe and Great Plains grasslands, regions where V. dubia recently became established.

Effects of Ventenata dubia removal on rangelands of northeast Wyoming

“…Because V. dubia invasion has been documented lowering species diversity (Jones et al 2018(Jones et al , 2020Novak et al 2015), we hypothesized some increase of species diversity with V. dubia control. Although removal of V. dubia resulted in large changes in cover for some species, such as P. smithii, we did not find a change in species richness 1 yr after treatment as a result of V. dubia removal in either study (P > 0.18; Table 4).…”

“…Ventenata dubia can reduce biodiversity of areas it invades (Jones et al 2018(Jones et al , 2020 and has negative impacts on wildlife and its habitat, namely birds, through trophic cascades (Mackey 2014). Similar to other invasive species, species richness and diversity were negatively correlated with increasing V. dubia cover (Jones et al 2018(Jones et al , 2020.…”

Forb community response to prescribed fire, livestock grazing, and an invasive annual grass in the Pacific Northwest Bunchgrass Prairie

“…Forb cover decreased over time as the cover of Ventenata dubia increased, adding evidence to showing negative impacts of invasive TA B L E 5 Relationships between Ventenata dubia and forb cover (%), species richness, and diversity for sampling years separately, and combined with simple linear regressions annual grasses (Melgoza et al, 1990;D'Antonio & Vitousek, 1992;Knapp, 1996;Ogle et al, 2003;Davies, 2011;McGranahan et al, 2012;Endress et al, 2019) including a decrease in native species richness (Ashton, et al, 2016;Jones et al, 2020). This supports the findings of Averett et al (2020), who also reported a decrease in native perennial forb cover from 2008 to 2016 on the PNB in different experimental sites from our study.…”

Climate Change and More Disturbed Land-Use Types will Further the Invasion of a Non-Native Annual Grass, Ventenata Dubia

“…In some situations, timing of hay harvest schedules had to be altered to avoid export losses due to V. dubia (Wallace et al 2015). V. dubia has been associated with a decrease in plant species richness and diversity in the Palouse prairie and Canyon lands (Jones et al 2020), and a decline in nesting success of insect-eating birds due to a loss of biodiversity in conservation lands in northern Idaho (Jones et al 2018).…”

“…Since this species is still relatively new to the region, little information has been published about its habitat niche and distribution potential. In the Paci c Northwest it was rst observed in wetter sites but has spread to drier habitats over the last 30 years (Jones et al 2020). Species distribution modeling (SDM) is a well-established technique to evaluate climate and environmental requirements of a species, and project the potential habitat range for the species of interest.…”