Submitted to: Wildland Shrub Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2006
Publication Date: N/A
Interpretive Summary: Evaluating the effects of management activities on vegetation in extensive rangelands with traditional methods requires much time and effort. Very large scale aerial (VLSA) imagery is an efficient tool for collecting the data required to evaluate these effects. We analyzed VLSA imagery collected from a survey of the U. S. Sheep Experiment Station along with soil and 68 years of fire history data to test whether VLSA imagery can be used to evaluate the effect of fire recovery interval on bitterbrush cover and density. The relationship between postfire recovery interval and bitterbrush cover and density were similar to those previously reported in the literature for eastern Idaho and indicate that analysis of VLSA imagery is an effective method for evaluating the impact of fire history on bitterbrush recovery.
Technical Abstract: Very large scale aerial (VLSA) imagery is an efficient tool for monitoring bare ground and cover on extensive rangelands. This study was conducted to determine whether VLSA images could be used to detect differences in antelope bitterbrush (Purshia tridentata Pursh DC) cover and density among similar ecological sites with varying postfire recovery periods. In 2005, VLSA images were acquired at 253 points from high bitterbrush potential ecological sites at the USDA-ARS, U.S. Sheep Experiment Station, Dubois, Idaho. For each image, fire history was classified and bitterbrush density and cover were measured. Bitterbrush cover in images with no recorded history of fire during the previous 68 yr (22 percent of all images) was 1.71 percent and density was 875 plant ha. Areas with postfire recovery interval between 10 and 68 yr (60 percentage of all images) had bitterbrush density (587 plant ha-1) and cover (1.23 percent) that were not different (alpha = 0.05) from areas with no fire history. Images with postfire recovery interval less than 7 yr (18 percent of all images) exhibited less bitterbrush cover (0.49 percent) and density (263 plant ha-1). These results are consistent with other studies of postfire bitterbrush recovery in eastern Idaho and indicate that analysis of VLSA imagery is an effective method for evaluating the impact of fire history on bitterbrush recovery.