Linaria dalmatica invades south-facing slopes and less grazed areas in grazing-tolerant mixed-grass prairie

Abstract

Identifying environments where invasive plants are most invasive is key to understanding causes of invasion and developing effective management strategies. In mixed-grass prairie, invasive plants are often successful in relatively wet, nitrogen-rich areas, and areas protected from grazing. Dalmatian toadflax, a common invader of mixed-grass prairie, can also be favored by high water and nitrogen availability, but is thought to be relatively unpalatable to cattle, and therefore favored by grazing. We used spatiallyadjusted model selection techniques to quantify relationships between toadflax cover (measured using very high-resolution aerial imagery), and relative snow deposition (estimated with a blowing snow model), slope, aspect, soil texture, and grazing intensity (estimated by proximity to water tanks). Toadflax was common throughout the 400 ha study site, occurring in 742 of 1,861 images. Toadflax cover was high on steeper slopes, particularly those with southern aspects. These two topographic variables were more effective in explaining toadflax distribution than modeled snow deposition, suggesting that factors other than snow deposition cause toadflax invasion on southfacing slopes. Toadflax cover was also high in areas further from water tanks, indicating that grazing may inhibit toadflax invasion. More broadly, this result suggests that grazing can reduce invasion of even relatively unpalatable species in ecosystems with long evolutionary histories of grazing.

Using invaded-range species distribution modeling to estimate the potential distribution of Linaria species and their hybrids in the U.S. northern Rockies

“…Linaria dalmatica was also modeled as most likely to occur in open areas dominated by grasses and in areas with reduced vegetative cover but more roads or other human-created disturbances. This agrees with published studies describing L. dalmatica invasion (e.g., Blumenthal et al 2012;Vujnovic and Wein 1997).…”

Density dependence, precipitation and biological control agent herbivory influence landscape‐scale dynamics of the invasive Eurasian plant Linaria dalmatica

“…Linaria dalmatica is a short-lived, herbaceous perennial that primarily invades well-drained, coarse-textured soils and is commonly associated with disturbed, sparsely vegetated habitats including roadsides, gravel pits, fields, waste areas, rockslides and other sloped areas (Robocker 1974;Vujnovic & Wein 1997;Blumenthal et al 2012). Seeds can germinate in the fall but more commonly germinate in the spring, and seedling establishment is higher in open areas devoid of competition (Grieshop & Nowierski 2002).…”

Composted manure application promotes long‐term invasion of semi‐arid rangeland by Bromus tectorum

“…Both progressive invasion of the site and treatment effects could also have been influenced by other processes, such as grazing management or changing climate, both of which can affect plant invasion in this ecosystem (Harmoney , Blumenthal et al. , , Prevey and Seastedt ). These temporal patterns demonstrate that invasion can take considerable time to become apparent following composted manure addition to otherwise undisturbed perennial grasslands.…”

“…Previous work at this site has suggested that cattle grazing can inhibit invasive species, likely by favoring competitive grass species (Blumenthal et al. ). Grazing effects on B. tectorum could differ, however, due to its distinct early‐season phenology, which limits exposure to grazing.…”