Comparison of 2 vegetation height methods for assessing greater sage-grouse seasonal habitat

Abstract

The 2015 Sage-Grouse Habitat Assessment Framework (HAF) was developed to evaluate habitat quality for sage-grouse (Centrocercus spp.), with the greater sage-grouse (C. urophasianus) as the primary focus of HAF evaluations and basis of the indicators in the HAF. Site-scale assessments of sage-grouse habitat can be completed using either data collection methods described in the HAF or core methods adopted by the U.S. Bureau of Land Management's Assessment, Inventory, and Monitoring (AIM) program. However, there is a discrepancy in how vegetation height is measured between HAF and AIM methods, which has led to confusion as to which protocol should be used and if the AIM height method is compatible with the HAF for habitat assessments. Our objective was to use simulations and data from multiple study areas to determine how often differences between the 2 methods would result in a different determination of quality for the vegetation-height habitat indicator. We confirmed that the AIM method generally yields lower estimates of height than the HAF method because it estimates mean vegetation height whereas the HAF method estimates mean maximum height (d = 0.031). However, differences between methods at the plot level most often were not substantial enough to lead to a different conclusion about the HAF vegetation-height indicator for habitat quality. There is value in implementing the AIM method because it is widely used for other monitoring purposes, and slight modifications to the AIM technique (i.e., increasing measurement frequency, adding measurements for both grasses and forbs) could improve usefulness for sage-grouse habitat assessments. © 2018 This article is a U.S. Government work and is in the public domain in the USA.