|Tsagaan Sankey, Temuulen|
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2008
Publication Date: 11/1/2008
Citation: Tsagaan Sankey, T., Moffet, C.A., Weber, K.T. 2008. Post-fire recovery of sagebrush communities: Assessment using SPOT5 and very large-scale aerial imagery. Rangeland Ecology and Management. 61:614-622. Interpretive Summary: Sagebrush cover is an important component of rangeland health and habitat quality in the sagebrush steppe, especially for sagebrush obligate wildlife species. Fire is an important tool for management of mountain big sagebrush communities, but has the effect of immediately reducing sagebrush cover. Few long term studies of sagebrush dynamics after fire have been conducted. By coupling fire history data with shrub cover data on sites with similar potential one can develop post fire sagebrush cover relationships. In this study, we have developed a remote sensing method for estimating total shrub cover, which is highly correlated with sagebrush cover. We have tested this method across a range of fire history and developed and shrub recovery relationship for mountain big sagebrush communities. These methods can be used in other sagebrush community types to develop recovery relationships for fire or other types of management. The method will also be useful for general shrub cover monitoring.
Technical Abstract: Much interest lies in the long-term recovery rates of sagebrush communities after fire in the western USA as sagebrush communities comprise millions of hectares of rangelands and important wildlife habitat. Little is known about post-fire changes in sagebrush canopy cover over time, especially at a landscape scale. We studied post-fire recovery of shrub canopy cover in sagebrush-steppe communities using spectral mixture analysis. Our study included 16 different fires that burned between 1937-2005 and one unburned site at the U.S. Sheep Experiment Station in eastern Idaho. Spectral mixture analysis was used with September 2006 SPOT5 satellite imagery to estimate percent shrub canopy cover within pixels, an approach that has not been commonly used in sagebrush studies. Very large-scale aerial (VLSA) imagery with 2-mm resolution was used for training and validation. SPOT5 imagery classification was successful and the spectral mixture analysis estimates of percent shrub canopy cover were highly correlated with the shrub canopy cover estimates in the VLSA imagery (R2= 0.91; p<0.0001). This successful application of spectral mixture analysis has important implications for the monitoring and assessment of sagebrush-steppe communities. Using the percent shrub canopy cover estimates from the classified SPOT5 imagery, we examined shrub canopy recovery rates since different burn years. Using piecewise regression, it was determined that shrub cover in mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) communities was recovered in 27 years after fire. The recovered shrub cover was 38.6 %. These results are consistent with other field-based studies in mountain big sagebrush communities.