Submitted to: Weed Science Society of America Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 8, 2003
Publication Date: February 9, 2004
Citation: Young, J.A., Clements, D.D., Harmon, D.N. 2004. Community succession among invasive, exotic weeds. In: Proceedings of the Weed Science Society of America Meeting Proceedings, February 09-12, 2004, Kansas City, Missouri. p. 39. Technical Abstract: Invasive, exotic weeds have become established on millions of hectares of rangeland in western North America. There is an abundance of scientific literature attesting to the magnitude of this invasion, but this literature largely deals with individual species and not assemblages of exotic weeds acting as phyto-sociological units in seral continuums. In such seral relationships the exotic weeds interfere with each other and interact with the environment to condition successional stages of dominance. The big sagebrush (Artemisia tridentata Nutt./bunchgrass communities of the Intermountain west provide examples of these concepts. Downy brome (Bromus tectorum L.) no dominates vast landscapes that were previously occupied by the native shrub and perennial bunch grasses. If you remove all the vegetation from big sagebrush/bunchgrass sites the first plants to invade will not be downy brome, but Russian thistle (Salsola targus L.), barbwire Russian thistle (S. paulsenii Litv.) and halogeton (Halogeton glomeratus [M. Bieb.) C. Meyer). All these species combine very abundant seed production and excellent seed dispersal mechanisms. After a single growing season, there will be an abrupt succession to dominance by exotic species of Brassicaceae. In turn there will be a gradual transition over a few years to dominance by downy brome. Changes in the potential of seedbeds to support germination govern these successional changes. Succession is reversible. Control of downy brome allows lower successional levels to express themselves, creating a different weed problem.