Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/18/2005
Publication Date: 2/15/2006
Citation: Harmon, D., Sanchez, D., Clements, C.D., Young, J.A. 2006. Cheatgrass seedbanks 30 years after the Hallelujah wildfire [abstract]. Proceedings Society for Range Management. 59:100. February 12-17, 2006, Vancouver, British Columbia. Interpretive Summary:
Technical Abstract: The Hallelujah Junction wildfire occurred on the Nevada-California border in July 1973. The fire burned in degraded big sagebrush (Artemisia tridentata)/bunchgrass communities with a significant understory of cheatgrass (Bromus tectorum). The shrubs had been damaged by an out-break of the sagebrush defoliator moth (Aroga websteri). Ignited by a dry lightning storm, the fire burned for about 1 week and covered about 16,000 hectares. On sites where the slope and rock cover permitted the use of rangelands drills, a mixture of crested and pubesent wheatgrass (Gramineae, Poaceae Agropyron intermedium var. trichophorum (Link) Halac.), sainfoin (Onobrychis viciifolia), alfalfa (Medicago sativa) and fourwing saltbush (Atriplex canescens) were seeded in the spring of 1975. The seeding was considered successful on most of the sites. It was so successful the available forage production exceeded demand for 25 years. There are islands in the predominant soil type where seeding was not conducted because of problems with turning the multiple drill hitches used in the seeding operation. Twenty-nine years after the wildfire and seeding, we used a bioassay technique to determine the number of germinate-able cheatgrass seeds per unit area of seedbed. Samples were taken from sites that were originally seeded and maintain a dominance of perennial grasses and sites of the same ecological potential that were not seeded and are currently dominated by cheatgrass. Over 2,000 cheatgrass seeds per square meter were recorded in the unseeded sites while only 158 cheatgrass seeds per square meter were recorded in the seeded sites. This 158 recorded cheatgrass seeds is still a significant factor in the succession of this site in any disturbance era. Even though more germinate-able cheatgrass seeds were found in the seedbed of unseeded sites compared to sites seeded 30 years prior, the seeded sites still maintain an undesirable seedbed with many germinate-able seeds with the potential to establish after any disturbance such as another wildfire. This demonstrates the importance of weed control after a fire disturbance even when the wildfire occurs within a previously seeded site that maintained an established seeded community.