-Canada Thistle: Lamar Valley, YNP
The Problem: Canada Thistle (Cirsium arvense), also known as creeping thistle, is a noxious weed that is very prevalent in the Greater Yellowstone Ecosystem and the Targhee National Forest. It crowds out native vegetation and spreads through rhizomes and by wind dispersed seeds. Seeds can remain viable in the soil for up to 20 years1, making management incredibly difficult.
-Canada Thistle (Cirsium arvense).
Outline: In order to obtain a spectral signature of Canada thistle, groundtruthing polygons were needed for analysis. Polygons were collected in the same fashion as the leafy spurge project. The majority of the data was collected near the confluence of Soda Butte Creek and the Lamar River. Most of the patches followed roads, disturbed creek cutbanks, and bison wallows. Many of the large dense patches were long and narrow, making it difficult get a training pixel of 100% thistle cover. After a few days walking around, some large, wide patches with 90% thistle cover were found near the confluence of Pebble Creek and the Lamar River.
1http://www.nps.gov/plants/alien/fact/ciar1.htm