COS 41-5
Influence of wildfire and post-fire seeding treatments on vegetation and insects in sagebrush-steppe habitats
Disturbance events often alter community composition and structure. A goal of post-fire habitat rehabilitation often is to restore disturbed habitats and communities to conditions that approximate the pre-disturbance state. The relative success of these activities is often measured by vegetation composition and structure, without any measure of how the habitat is utilized by wildlife after a rehabilitation treatment. The sagebrush-steppe of the Intermountain West is a large ecosystem type that has been extensively altered by wildfires fueled by invasive annual grasses. We examined the influence of wildfire and post-fire seeding on insect communities within sagebrush-steppe habitats in southwest Idaho by comparing vegetation and insect assemblages among three condition classes: burned areas that were seeded after fire, burned areas that were not seeded, and nearby unburned areas that approximated conditions prior to burning. We determined vegetation composition and cover values and captured and identified >22,000 insects to family using flight and pitfall traps within 35 field plots in 2010 and 2011.
Results/Conclusions
Our preliminary results indicate that post-fire seeding changed the vegetation composition at burned plots by increasing the percent coverage of bunchgrass and forb species relative to that of burned-unseeded as well as unburned sagebrush-steppe habitats. Reseeding did not achieve the vegetation composition of unburned plots, especially because it lacked the pre-fire shrub component. Some insect families were strongly associated with specific vegetation components such as bunchgrasses or forbs. Despite relationships between vegetation composition and insects, there was not strong evidence that insect assemblages at burned-seeded plots were different from those at burned plots that were not seeded, though the vegetation at the seeded plots contained higher percent coverage of seeded bunchgrasses and native forbs. However, insect assemblages at plots that were burned, regardless of seeding, were different from those at plots that were not burned. Our preliminary results indicate that wildfire altered insect assemblages by removing insects that are sagebrush specialists. Additionally, post-fire seeding did not successfully restore the vegetation (especially sagebrush) or insect assemblages at our sites. However, insight into specific relationships between insect families and vegetation components from this study may inform future attempts to restore habitat for specific insect groups, such as pollinators.