Skip to main content
ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #332230
Title: Critical evaluations of vegetation cover measurement techniques: a response to Thacker et al. (2015)

Author
item Karl, Jason
item KARL, MICHAEL - Bureau Of Land Management
item MCCORD, SARAH - New Mexico State University
item KACHERGIS, EMILY - Bureau Of Land Management

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Coordinated monitoring activities are paramount to achieving successful management and restoration of rangelands across land owners and managing agencies. To accomplish this it is necessary to reconcile monitoring methods that have arisen among disparate programs. In this spirit, we welcome the comparison Thacker et al.1 make between line-point intercept (LPI) and a  Daubenmire-frame (DF) technique for estimating vegetation cover in sagebrush (Artemisia spp.) systems. However, we find Thacker et al.’s descriptions of their methods, analysis and results, and discussion are incomplete and cannot support their conclusions that 1) cover estimates from DF and LPI methods are incomparable, and 2) both DF and LPI methods should be conducted when assessing or monitoring sage grouse habitat. Evaluations of vegetation measurement methods should be conducted and reported in a rigorous manner, provide a thorough review of previous studies, and discuss how new results contribute to existing knowledge. Additionally, data used in method comparison studies should be made available in public data repositories so that other researchers may investigate and incorporate their data into further method comparison studies. To understand how monitoring methods relate to each other comparison studies must follow and thoroughly describe a rigorous evaluation process, including but not limited to: clearly stated definitions of the indicators being measured, thorough training and calibration of the data collectors, appropriate statistical analysis, and interpretation of results in a broader management and scientific context. Thacker et al.’s study falls short in these respects. Namely, their conclusion that cover estimates from DF and LPI are not comparable is based on a faulty assumption that these techniques measure the same indicator and on an incomplete analysis of their data.

Technical Abstract: Comparison studies are necessary to reconcile methods that have arisen among disparate rangeland monitoring programs. However, Thacker et al.'s study comparing Daubenmire frame (DF) and line-point intercept (LPI) methods for estimating vegetation cover ignores definitional differences between what the two methods measure and omits critical information that could affect the results they report. Additionally, their results are inadequate to support their conclusions that DF and LPI are not comparable and that both methods should be implemented for sage grouse habitat studies. Rather than implementing both methods, effort should instead focus on ensuring rigorous, thorough sampling for one selected method.