Recovery of biological soil crusts following wildfire in Idaho

Invasion of sagebrush steppe by exotic annual grasses has modified the structure of shrubland communities over much of the western United States by increasing fuel loads and therefore the frequency of wildfire. Active revegetation with perennial species that encourage the growth of biological soil crusts is critical on many burned sites to prevent dominance by exotic, weedy vegetation. However, active regeneration is likely to lead to a disruption of the soil surface and impact adversely on soil crust communities which are important for stability and functioning of shrub communities. We examined the recovery of biological soil crusts on sagebrush steppe following wildfire. Burning resulted in significantly reduced shrub cover and enhanced annual grass and annual forb cover compared with unburned sites. Burning also resulted in substantially reduced diversity and richness of crust taxa, increased cover of short mosses, but reduced cover of lichens and tall mosses growing on the shrub hummocks. Post-fire recovery of perennial grasses and biological soil crusts was greatest on seeded sites compared with unseeded sites dominated by exotic grasses, despite the disturbance associated with the rangeland seeding treatment. Our results indicate that seeding is necessary to facilitate recovery of biological soil crusts and hasten the development of the perennial component of the shrubland and therefore increase landscape structure. These findings suggest that seeding perennial grasses and resting from livestock grazing reduces exotic annual grasses after fire and benefits native mosses.