Design and Analysis of Rangeland Experiments Along Continuous Gradients

Abstract

Measuring the effects of grazing intensity on the structure, composition, and function of grassland ecosystems has been a perennial challenge. Space limits replication, few replicates limit statistical power, and categorical treatments limit interpretation of effects among treatment levels. Treating grazing as a continuous rather than categorical variable can permit large-scale experiments to be conducted with fewer constraints on treatment replication to maintain statistical power. Using power analysis on a grazing experiment recently initiated in Grasslands National Park of Canada, we demonstrate that the continuous approach permits the use of fewer pastures, while maintaining the large pasture size required to allow realistic grazing behavior by cattle and improving our ability to answer biologically relevant questions regarding grazing effects on grassland ecosystems. We contend that this approach, when applied to grazing experiments, will help test hypotheses related to how grassland ecosystems respond to a gradient of disturbance regimes.