Barbwire Russian Thistle Seed Germination

Abstract

Barbwire Russian thistle (Salsola paulsenii) is the dominant species of severely degraded plant communities in the most arid portions of the Great Basin. The seed germination of this alien annual plant was compared with that of common Russian thistle (S. iberica). In general, the two species of Salsola have similar germination characteristics. However, there were important differences that apparently favor barbwire Russian thistle in arid environments. These advantages were (a) less restrictive afterripening requirements that allow some germination at a broader range of temperature sooner after maturity, (b) more rapid germination at low temperatures during the first 10 days of incubation, and (c) dehiscence of seeds without the necessity of the plants uprooting and tumbling. Barbwire Russian thistle (Salsola paulsenii) has only scant coverage in range management literature because only recently has it been widely recognized in the western United States as a separate species from Russian thistle (S. iberica). Russian thistle is one of the most widely occurring alien annuals in western North America. This weed was first introduced into the United States in 1873 or 1874 in flax (Linum sp.) seed brought from Russia and sown near Scotland, South Dakota (Stevens 1943; Robbins et al. 1952). Several Canadian proviinces and 16 western states of the United States were infested by 1895. Russian thistle now infests all of the western portion of North America. Barbwire Russian thistle is native to southeastern Russia and central Asia (Allen 1964). It was probably introduced to the far western United States sometime between 1891-1913 (Beatley 1973). Coville (1893) did not collect barbwire Russian thistle in his extensive botanical explorations on the Death Valley Expedition of 1891. Alice Eastwood, the noted California botanist, collected barbwire Russian thistle near Barstow, California in 1913 (Beatley 1973). Barbwire Russian thistle occurs in California, Nevada, and Utah (Munz 1968; Anonymilous 1969). We do not know exactly when barbwire Russian thistle invaded the Carson Desert of northwestern Nevada. During the 1960's Beatley (1971) established that there were distinct taxonomic entities of Russian thistle in the southern Great Basin. Publication of Beatley's work stimulated our interest and Authors are range scientists. U.S. Department of Agriculture Science and Education Admiiinistration. Agricultural Research. Renewable Resource Center, Univ. of Nevada. 920 Valley Rd.. Reno 89512. This study is a contribution from The U.S. Dep. Agr.. SEA. AR., and the Agr. Exp. Sta.. Univ. of Nevada. Reno. Journal Series No. 423. Manuscript received August 29. 1978. observation in the Carson Desert and we observed what appeared to be the last stages of replacement of Russian thistle by barbwire Russian thistle in the desert rangeland communities of the area. Such replacement has not occurred in many ruderal communities or in areas of irrigated, intensive agriculture. Previous studies (Young and Evans 1972; Evans and Young 1972) have enumerated many of the seed and seedbed ecology characteristics of Russian thistle. The purpose of this investigation was to conduct similar comparative studies of the seed and seedbed ecology of barbwire Russian thistle.