RE: Invasives we loathe. In the Great Basin and much of the Intermountain west: cheatgrass. Cheatgrass readily invades disturbed soil and has spread throughout the West in the wake of grazing, agriculture and development. An invasive annual grass, it readily displaces native bunchgrasses and forbs, and steers plant succession in new directions.
Because cheatgrass cures out earlier in the season than native bunchgrasses (hence the term 'cheat' from livestock growers), it creates a layer of fine, dry fuels throughout the shrub-steppe understory that not only carries fire better, but allows rangelands to burn earlier in the season. Where cheatgrass dominates the understory, the result is vastly larger, sometimes earlier, and often more severe range fires than were seen historically. Where these severe range fires burn hot enough to kill the shrub overstory, it becomes increasingly difficult to naturally re-establish native plants, as few green patches are left to provide seed sources. Yet what does readily re-establish after such fires is more cheatgrass, other annual grasses and invasive weeds. With this second generation of non-native grasses we often see a complete shift from native shrub-steppe and perennial grasslands to uniform non-native annual grasslands that burn frequently, at intervals of three to five years--hence sustaining the non-native annual grasslands. Cheatgrass appears to be an "entry-weed" for other exotic species, such as medusahead wildrye, halogeton, yellow star thistle and skeleton weed. Ultimately, cheatgrass is contributing to the destruction of western sagebrush shrub-steppe habitat (think greater sage-grouse, pygmy rabbit, Brewer's sparrow, sage sparrow, sage thrasher, sagebrush vole, sagebrush lizard and pronghorn--all sagebrush dependent species). Global warming and drought may also be factors in cheatgrass getting the upper hand in native shrub-steppe and grasslands. I'm also none too fond of spotted knapweed, a coarse invasive that has taken over many of the native grasslands of western Montana. Brought to Montana originally by bee-keepers as an outstanding source of nectar for honey (it really does make yummy honey), spotted knapweed has turned many of our lovely bunchgrass- and wildflower-strewn hillsides into knapweed monocultures. Course and dense, it is miserable to walk through and only domestic goats seem to have any taste for it. Control requires herbicides or intensive management efforts via timed mowings, intensive grazing by goats or sheep, and introducing knapweed pests as bio-controls. Knapweed also seems to open the door for other noxious weeds, such as leafy spurge. And the ripples continue... I'll stop now. Hope this helps! Christine Paige, M.Sc. Wildlife Biologist Ravenworks Ecology Stevensville, MT
