干旱区生态环境知识资源中心

QuestionHow does type of disturbance alter plant community composition when an invasive species with high intrinsic population growth rate is present? The sagebrush steppe is a cold semi-arid steppe dominated by the native shrub Artemisia tridentata Nutt., native bunchgrasses, and has been invaded by the non-native winter annual Bromus tectorum L.

LocationSagebrush steppe, Montana, USA.

MethodsWe assessed the effect of fire and soil disturbance, due to bulldozing to create a firebreak, on the resilience of plant communities and their resistance to invasion by B.tectorum. Plant species richness and species composition were monitored for 3years at two sites post-fire and firebreak construction.

ResultsBurned plant communities were resilient and had similar native grass cover and native species richness compared with the unburned sites after 3years. Soil disturbance from firebreak construction resulted in species composition that was distinct and had lower native grass cover. Type of disturbance also affected the community’s resistance to B.tectorum. Bromus tectorum cover was similar in burned and unburned areas, but increased up to three times and remained high where soil disturbance occurred, suggesting a shift to an alternative state.

ConclusionIn this northern portion of the sagebrush steppe, communities with native plant cover were resilient to fire but not soil disturbance, which facilitated B.tectorum increase and a transition to an alternative state. In areas of high native plant cover, management tactics should avoid soil disturbance.