Rush Skeletonweed (Chondrilla juncea L.) is a deep-rooted perennial
forb in the family Asteraceae, growing
1m in height. It infests well-drained, light soils commonly found in the
mountain foothills and canyon grasslands of the Northwest, and currently
infests several million acres of rangeland and cropland in Washington, Oregon, Idaho,
and Montana. The species can spread locally by rhizomes and longer distance via
wind with a pappus-bearing seed. Our research objective was to produce a dispersal
model that would aid land managers in their efforts to find new populations of
this invasive plant species. A study area including the Salmon River Canyon,
Idaho was used to develop wind dispersal model for rush skeletonweed. Wind
speed and direction collected from RAWS USA climate archive were used to
construct wind maps in order to create the wind dispersal models. Bivariate interpolation
technique was used at 100x100m resolution and then converted to 10x10m
resolution in the IDRISI software to create wind maps. The wind maps were then
used in a multi-layer perceptron routine, along with aspect, elevation, and
vegetation to produce predicted wind speed and wind direction. Predicted wind
speed and direction were subsequently used in IDRISI GIS software using five area
polygons as starting points to run the DISPERSE module. Several runs of the
dispersal module were considered to evaluate settings of module parameters. Finally,
wind dispersal maps were created that provide information about how far the
rush skeletonweed seeds move and in which direction.  The model resulted in 80-90 percent coverage of
known infestations and showed the expected pattern and directionality of seed
movement for the five areas. The distance of seed dispersal ranged from 4 to 12
km and consistently moved in the direction of the wind for the canyon
grasslands of central Idaho.