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Modeling Invasive Annual Grass Abundance in the Cold Desert Ecoregions of the Interior Western United States
مدل سازی توده های سالانه تهاجمی چمن در مناطق ساحلی سرد صحرای غربی ایالات متحده غربی-2020 Invasive annual grasses, primarily Bromus tectorum, are a severe risk to native vegetation of the intermountainWest.
Once established, annual grasses alter natural fire regimes and outcompete natives until,
in some places, they become the overwhelming dominant. We developed a regional spatial model
encompassing eight ecoregions to indicate the relative abundance of invasive annual grass at five levels
of canopy cover. We used field sample data representing invasive annual grass abundance to build and
calibrate the model. Explanatory variables, represented as map inputs, included image indices, climate,
landform, soil, and human-induced surface disturbance. As a novel modeling approach, we built multiple
models based on classes of invasive annual grass cover abundance were developed individually and then
combined into a final 90-m pixel resolution model that indicates locations relative to invasive annual
grass abundance into classes of < 5%, 515%, 1625%, 2645%, and > 45% cover. Each component model
was validated using held-out sample data, and relative accuracy was 86%, 74%, 62%, 62%, and 60%,
respectively, with an overall kappa of 0.773. The Columbia Plateau, Northern Basin and Range, and Snake
River Plain ecoregions appear to have the greatest overall proportions (4862%) mapped within at least
one of the invasive cover categories. Overlay of the resulting model with major vegetation types indicated
> 50 major vegetation types that are affected by current distribution of annual grasses and are at
risk of expansion. Among these, Intermountain Basins, Big Sagebrush Steppe, and Columbia Plateau
Steppe and Grassland each consistently scored high for invasive risk where they occur. Spatial models of
this type should assist with rangeland restoration and for decisions involving placement of infrastructure,
vegetation treatments where further surface disturbance could trigger additional cheatgrass
expansion. Options exist for extending this model, using climate projections over upcoming decades, to
indicate areas of increasing risk for invasion. Key Words: ecological condition | ecological integrity | human footprint | human modification | invasive annual grass | weeds |
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