Sampling Bias Exaggerates a Textbook Example of a Trophic Cascade

• Main Authors: Brice, Elaine M., Larsen, Eric J., MacNulty, Daniel R.
• Other Authors: Wiley-Blackwell Publishing Ltd.
• Format: Text
• Language: unknown
• Published: Hosted by Utah State University Libraries 2021
• Subjects: aspen; carnivore; elk; non-random sampling; predator indirect effects; preferred browsing height; sampling bias; trophic cascade; ungulate; wolf; Agriculture; Ecology and Evolutionary Biology; Forest Sciences; Genetics and Genomics; Plant Sciences; Canis lupus
• Online Access: https://digitalcommons.usu.edu/aspen_bib/7958; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=8959&context=aspen_bib

Understanding trophic cascades in terrestrial wildlife communities is a major challenge because these systems are difficult to sample properly. We show how a tradition of non-random sampling has confounded this understanding in a textbook system (Yellowstone National Park) where carnivore [Canis lupus (wolf)] recovery is associated with a trophic cascade involving changes in herbivore [Cervus canadensis (elk)] behaviour and density that promote plant regeneration. Long-term data indicate a practice of sampling only the tallest young plants overestimated regeneration of overstory aspen (Populus tremuloides) by a factor of 4–7 compared to random sampling because it favoured plants taller than the preferred browsing height of elk and overlooked non-regenerating aspen stands. Random sampling described a trophic cascade, but it was weaker than the one that non-random sampling described. Our findings highlight the critical importance of basic sampling principles (e.g. randomisation) for achieving an accurate understanding of trophic cascades in terrestrial wildlife systems.