Submitted to: Popular Publication
Publication Type: Popular Publication
Publication Acceptance Date: 7/29/2004
Publication Date: 8/2/2004
Citation: Young, J.A., Clements, C.D., Harmon, D.N. 2004. Cheatgrass seedbanks. Reno Gazette Journal. 08/16/04.
Technical Abstract: Cheatgrass (Bromus tectorum) is a highly invasive weed innthe Intermountain west that provides a fine textured, early maturing fuel that increases the rate, spread, and occurrence of wildland fires. Early researchers estimated that as little as 4 cheatgrass plants per square foot could limit the growth of perennial grass seedlings. Perennial grasses are very important in suppressing cheatgrass and other exotic weeds on Nevada rangelands. It is important for individuals engaged in reclamation and restoration seedings to have the means of estimating the level of cheatgrass competition for a given site as they design weed control strategies before seeding. Estimating potential cheatgrass competition is not a simple process. Cheatgrass seeds are not initially dormant, but a portion of the annual seed crop does not germinate in the field and develops an acquired dormancy that can last for several years. This buildup of viable but dormant seeds is called a seedbank. You can have sites that on given years have no cheatgrass because of drought, but have seedbanks of both dormant and germinable seeds. We have started a project to develop procedures that land managers could use in the field to estimate the size and nature of cheatgrass seedbanks. The current experimental procedures used to estimate cheatgrass seedbanks was developed by ARS some years ago and involves bioassaying the litter and soil in the greenhouse coupled with nitrate and gibberellin enrichment of the sample over time. Obviously land managers lack facilities, time, and materials for such a test. We started testing over 1,000 samples in 2003 from northern Nevada and northeastern California from sites that range from 3,700 feet to 7,200 feet in elevation that represent the sagebrush, pinyon/juniper woodlands, and salt desert zones. These tests are still in progress, but the preliminary results are interesting. There were actually very few sites without cheatgrass, with the average cheatgrass seedlings from over 1,000 samples at 200 per square foot that ranged from 0-1,500 per square foot. Remember, you are in serious trouble of successfully seeding perennial species when cheatgrass densities are as few as 4 per square foot. At this time there are no glaring, easily measured, or estimate of the size and nature of cheatgrass seedbanks, but there are several promising leads.