A comparison of two vegetation height measurement methods for applications to sage grouse habitat evaluations

TitleA comparison of two vegetation height measurement methods for applications to sage grouse habitat evaluations
Publication TypeConference Proceedings
Year of Publication2017
AuthorsDi Stefano SF, Stauffer N, Karl JW, McCord S
Conference Name70th Annual Society for Range Management Meeting
VolumeJan 29 - Feb 02, 2017
Date Published01/2017
Conference LocationSaint George, Utah
ARIS Log Number337124

The conservation of Greater Sage-Grouse (Centrocercus urophasianus) habitat has become a serious management issue for U.S. federal land agencies given competing land uses and ecological change across the American West. This drives a need for data collection in Sage-Grouse habitat to assess habitat condition in a consistent manner. The 2015 Sage-Grouse Habitat Assessment Framework (HAF), describes site-scale habitat suitability for Sage-grouse seasonal habitats, in part, by height of sagebrush and perennial grasses and forbs. The height method described in the HAF (average of maximum plant heights) is different from the core vegetation height method (average of maximum plant heights within a series of fixed-radius cylinders) adopted by the BLM’s Assessment, Inventory, and Monitoring (AIM) program and the NRCS’s National Resources Inventory. Given the widespread implementation of the core methods, there may be benefits to using these data to complete habitat suitability assessments for Sage-Grouse. We compared the HAF and core height methods for shrubs, forbs, and grasses to evaluate if the core height method could be used to characterize Sage-Grouse habitat, using data from sites across the western U.S. where both methods were applied at each survey plot. We found a positive correlation between herbaceous and woody heights at the plot level. Individual within-plot measurements had a weaker correlation due largely to differences in which plants were measured with each method. We observed that the core method underestimated height compared to HAF as expected based on measured plant component. Simulations of the two height methods confirmed that, although they measure different indicators, the two indicators are strongly correlated. We therefore conclude that core vegetation height data are compatible with HAF habitat suitability evaluation. Where core data are already being gathered, we recommend using the core vegetation height method to satisfy HAF habitat suitability evaluations instead of collecting additional height measurements.