Big Sagebrush Seed Bank Densities Following Wildfires By Charlie D. Clements and Dan Harmon Authors are Rangeland Scientist and Agricultural Research Science Technician, USDA-ARS Great Basin Rangelands Research Unit, 920 Valley Road, Reno, NV 89512 charlie.clements@ars.usda.gov
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ig sagebrush (Artemisia spp.) is a critical shrub to many wildlife species including sage grouse (Centrocercus urophasianus), mule deer (Odocoileus hemionus), and pygmy rabbit (Brachylagus idahoensis). Big sagebrush is killed by wildfires and big sagebrush seed is generally short-lived and do not survive wildfires. Opinions continue to differ on the importance of seeding big sagebrush following wildfires from “we have plenty of sagebrush” to “we have lost millions of acres of sagebrush”. Another opinion that differs is whether big sagebrush has the ability to build seed banks and return following wildfire events. This is important as big sagebrush is a common species purchased and seeded
chance, rate, spread and season of wildfires throughout the Intermountain West. Pioneer USDA-ARS researchers, James A. Young and Raymond Evans reported that when conducting soil bioassay and germination tests of over 1,000 surface soil samples from burned habitats, that no big sagebrush emerged, suggesting that big sagebrush does not build persistent seed banks. The top three plant communities in the Great Basin are dominated by Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis/bunchgrass communities 54%, followed by salt desert shrub communities 28%, and mountain brush 9%. The loss of Wyoming big sagebrush following wildfires is very apparent on Nevada rangelands. The return of big sagebrush to a community following wildfires can be a very slow process, especially with the increase in wildfire frequencies throughout the Intermountain West, largely from cheatgrass fueled wildfires. Due to the various conversations concerning big sagebrush
in northwestern Nevada that burned in wildfires that year during the summer months to test any possible seed bank potential of big sagebrush (Figure 2). The first site, Empire Fire, is located 75 miles north of Reno, NV and is a degraded Wyoming big sagebrush habitat with an understory dominated by cheatgrass, with a sparse density of bluegrass (Poa secunda), squirreltail (Elymus elymoides), and Indian ricegrass (Achnatherum hymenoides). The second site, Sand Hills Fire, is located 10 miles north of Reno, NV and is a mountain big sagebrush (Artemisia tridentata ssp. vaseyana) community in good to excellent ecological condition. Other dominate shrubs at this site are antelope bitterbrush (Purshia tridenata) and Golden Currant (Ribes aureum). Sandberg bluegrass (Poa secunda formerly sanbergii) dominates the understory. Following the wildfires that took place in these two habitats we established 54 paired 10’ x 10’ plots at each site at the north and south end of the burned habitat. Nine paired plots were established at 3’ from the unburned fires edge and again at the 30’ and 100’ distance (9 x3 = 27 paired plots x 2 directions = 54). At each paired plot, one plot was seeded (0.10 lbs/ac rate) to the occurring big sagebrush species for that site. The other plot was bioassayed (surface soil collected) and brought back to the greenhouse for germination tests, 5 bioassay tests per plot were conducted.
Figure 1. Former Big sagebrush/bunchgrass community converted to annual grass dominance. Despite attempts to seed and transplant big sagebrush back into this community, without extensive/high cost weed control you have no chance of success.
in restoration/rehabilitation efforts throughout the Intermountain West. Formerly big sagebrush/bunchgrass communities that provided critical habitats to wildlife and sustainable grazing resources have been converted to annual grass dominance. With the increase in wildfire frequency throughout the Intermountain West from cheatgrass (Bromus tectorum) fueled wildfires, many habitats have been converted to cheatgrass dominance with no sight of shrub return, especially Wyoming big sagebrush (Figure 1). Cheatgrass has increased the
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seed banks and its’ ability to return following wildfires we initiated a study back in 2006 to address this concern. In the sum- Figure 2. Southern edge of the 2006 Empire Fire. Wyoming big sagebrush seeding failed and mer of 2006 we no big sagebrush seed bank was recorded. Without a successful rehabilitation of long-lived selected two areas perennial grasses, the chances of any real return of big sagebrush at this site are slim to none
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