Becky K. Kerns1, Claire Tortorelli2, Ty Nietupski2, Michelle Day2, Luke Ridder3, Lila Leatherman2, Meg Krawchuk2, Lesley Morris3, Bridgett Naylor1 and John Kim1
1US Forest Service, Pacific Northwest Research Station, Corvallis, Oregon, USA
2College of Forestry, Oregon State University, Corvallis, Oregon, USA
3College of Agricultural Sciences, Oregon State University, La Grande, Oregon, USA
The transformative ecological and socioeconomic impacts of invasive exotic annual grasses (EAG) have been long recognized in many ecosystems of the Americas, Australia, and Pacific islands. In western North America, EAGs such as Bromus tectorum have been highly problematic for decades in the iconic and vast sagebrush-steppe ecosystems. A recent EAG, Ventenata dubia or ventenata, has invaded these aridlands, but also threatens a wider range of dry interior North American ecosystems. Like many EAGs, ventenata has the potential to drastically alter biodiversity, livestock forage, fuel conditions and fire regimes, threatening multiple resources and ecosystem functions. We recently launched a series of studies focused on the Blue Mountain Ecoregion (BME), interior Pacific Northwest USA (Fig. 1) to examine how the ventenata invasion is transforming this ecoregion now and in the future.
Our 27 compiled data sources and new field surveys show ventenata is found from 392-1808 m in environments and plant community types ranging from forests, woodlands, shrub-steppes to meadows (Fig. 1). We used these data and leveraged cutting edge spatio-temporal satellite image fusion methods to estimate the species’ unique landscape phenology to determine past and present extent across the BME validated with known occurrences. This will allow us to explore multiple aspects of the invasion, understand environmental and disturbance drivers, and provide information to fire managers regarding novel and increasingly hazardous fuel conditions. We also combined this spatially explicit information with other data to feed into the first species distribution model for ventenata in the western USA, allowing us to compare its climate niche to the native range (Europe, North Africa), explore how future climates may alter habitat suitability, and project invasion estimates into the future. We are now simulating how fuels, fire regimes, and fire effects may shift across the region under future climate change.
We have also conducted fine-scale investigations of ventenata dynamics, fire, and biodiversity in the BME’s low fuel pyrophobic scablands and native bunchgrass ecosystems. These extensive ecosystems are important landscape components of forests in terms of both their ecology and fuel structure, which are being rapidly altered by the invasion (Fig. 2). Our bunchgrass prairie project explored how ventenata may respond to both prescribed fire and grazing. Newly proposed work will allow investigation into community susceptibility to invasion and delve more deeply into abiotic and biotic interactions.