Post-fire Recovery of Wyoming Big Sagebrush Steppe in Central and Southeast Montana

摘要

Big sagebrush (Artemisia tridentata Nutt.) steppe is a widespread habitat throughout eastern Montana and supports several sagebrush-dependent species including Greater Sage-grouse (Centrocercus urophasianus). We sampled 24 burned-unburned paired sites in central and southeastern Montana dominated by Wyoming big sagebrush (ssp. wyomingensis). Time since fire ranged from 4 to 67 years. Prescribed burns and wildfires typically resulted in the complete mortality of big sagebrush. We found negligible post-fire Wyoming big sagebrush recovery for 17 of the 24 sites and the oldest burn (67 years) was only 8 percent recovered. Perennial grass cover increased 27 percent and 20 percent following prescribed fire and wildfire, respectively; western wheatgrass (Pascopyrum smithii) accounted for most of this increase. Annual grass cover increased by 11 percent due primarily to field brome (Bromus arvensis, formerly B. japonicus). Plant species richness significantly declined in burned plots compared to unburned controls. There was no change after burning in overall sub-shrub or forb cover or the density of Cichorieae forbs that are important for successful Greater Sage-grouse brood rearing. Managers concerned about Greater Sage-grouse and other sage-dependent species should be extremely cautious with prescribed burns and wildfires in this region. Fire will likely eliminate sagebrush habitat, increase weedy annual grass cover and reduce species richness; sagebrush cover could take a century or more to recover to pre-burn conditions.