Experimental and environmental factors affect spurious detection of ecological thresholds

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Threshold detection methods are increasingly popular for assessing nonlinear responses to environmental change, but their statistical performance remains poorly understood. We simulated linear change in stream benthic macroinvertebrate communities and evaluated the performance of commonly used threshold detection methods based on model fitting (piecewise quantile regression [PQR]), data partitioning (nonparametric change point analysis [NCPA]), and a hybrid approach (significant zero crossings [SiZer]). We demonstrated that false detection of ecological thresholds (type I errors) and inferences on threshold locations are influenced by sample size, rate of linear change, and frequency of observations across the environmental gradient (i.e., sample-environment distribution, SED). However, the relative importance of these factors varied among statistical methods and between inference types. False detection rates were influenced primarily by user-selected parameters for PQR (τ) and SiZer (bandwidth) and secondarily by sample size (for PQR) and SED (for SiZer). In contrast, the location of reported thresholds was influenced primarily by SED. Bootstrapped confidence intervals for NCPA threshold locations revealed strong correspondence to SED. We conclude that the choice of statistical methods for threshold detection should be matched to experimental and environmental constraints to minimize false detection rates and avoid spurious inferences regarding threshold location.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Experimental and environmental factors affect spurious detection of ecological thresholds
Series title Ecology
DOI 10.1890/11-0516.1
Volume 93
Issue 1
Year Published 2012
Language English
Publisher ESA (Ecological Society of America)
Publisher location Ithaca, NY
Contributing office(s) Leetown Science Center
Description 7 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecology
First page 17
Last page 23
Additional Online Files (Y/N) N