Ecological threshold and environmental management: A note on statistical methods for detecting thresholds

Abstract

Many statistical models are available for detecting and quantifying ecological thresholds. The proper model can be selected through the comparison of the goodness-of-fit of multiple alternative models to the same data. In the context of selecting the appropriate threshold model, three sources of information should be used: patterns in model residuals, model predicted versus observed, and the posterior change point distributions. Applying alternative models to several ecological metrics measured along a total phosphorus gradient from a mesocosm experiment conducted in the Everglades, I conclude that changes in these metrics along the gradient are more likely to be gradual. The previously found strong threshold response is likely a result of the use of the step function model.