Methods alter interpretation of treatment impacts on winter-fat shrublands

Abstract

Monitoring shrubland vegetation change is important to rangeland assessment. Methods used to document shrubs vary with the intended use of information and the unit of observation. This study documents different interpretations of winterfat (Ceratoides lanata (Pursh.) J.T. Howell) response to defoliation, grazing history, and community position treatments from 1992 through 1994 when the interpretations were based upon 2 different methods of observation. In some cases, results from observations of individual winterfat plants differed from results that were based on unit-area observations. Individual plants did not reflect the same impacts of grazing history that were found from observing the collective response of plants in 11-m2 plots. Although plant results reflect impacts on individuals, plot results can indicate impacts of shrub canopy on surrounding vegetation as well. Comparisons of studies using different means of observation may lead to conflicting interpretations unless these effects are recognized.