Vegetation Impacts of Recurring Fires on Sagebrush Ecosystems in Washington: Implications for Conservation and Rehabilitation

Authors

J. D. Bakker, University of WashingtonFollow
P. W. Dunwiddie, University of WashingtonFollow
S. A. Hall, The Nature ConservancyFollow
J. R. Evans, The Nature ConservancyFollow
G, M. Davies, University of GlasgowFollow
E. Detterweiler-Robinson, University of New MexicoFollow

Date of this Version

2011

Document Type

Article

Citation

JFSP Project, Final Report 08-1-5-20

Comments

US government work.

Abstract

Thousands of hectares of high quality sagebrush shrub-steppe burned in south-central Washington in 2000 and 2007, particularly on the Arid Lands Ecology Reserve (ALE) on the Hanford Reach National Monument. Extensive rehabilitation efforts took place on ALE to control invasive species and establish native species following each of these fires. Permanent vegetation monitoring plots were established throughout this area in the mid-1990s, remonitored in 2001-2004, and monitored again in 2009-2010. This combination of rehabilitation treatments and monitoring provided a unique opportunity to better understand the individual and cumulative effects of recurring fires and restoration in this landscape. We investigated changes in vegetation and biological soil crust (BSC) cover over time and assessed the performance of restoration plantings of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis). Repeated fires have re-structured and simplified plant communities. Community responses to repeated fires and restoration treatments depend on the traits of the key species present. For example, high elevation communities are resilient to repeated fire as the dominant species are able to resprout after burning, whereas low elevation communities are strongly affected because big sagebrush is unable to resprout after burning. Low elevation areas that have lost their shrub component are unlikely to be dominated by shrubs again in the near future without significant active management. Vegetation dynamics in the sagebrush shrub-steppe can be related to the balance between grasses and shrubs and to the degree of invasion by non-native species. BSC cover and composition differ between successional stages and are affected by various abiotic and biotic factors. The effectiveness of sagebrush plantings varies among stocktypes in both seedling survival and economic costs. Given the large scale of these fires, active management is essential if the re-establishment of a shrub component is desired at low elevation sites. Our results can inform immediate management decisions regarding present and future post-fire habitat rehabilitation measures on ALE and other shrub-steppe sites, and provide critical insight into the long-term dynamics of this significant ecosystem.