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Related Experiment Video

Updated: Oct 14, 2025

Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout Salvelinus namaycush from Its Prey

Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout Salvelinus namaycush from Its Prey

Published on: August 29, 2014

Sampling bias exaggerates a textbook example of a trophic cascade.

Elaine M Brice¹, Eric J Larsen², Daniel R MacNulty¹

¹Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, USA.

Ecology Letters

|November 8, 2021

Summary

Non-random sampling overestimates trophic cascades in Yellowstone, masking the true impact of wolf recovery on elk and aspen regeneration. Random sampling is crucial for accurately understanding these complex ecological interactions.

Keywords:

aspen carnivore elk non-random sampling predator indirect effects preferred browsing height sampling bias trophic cascade ungulate wolf

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Area of Science:

Ecology
Wildlife Biology
Conservation Science

Background:

Trophic cascades in terrestrial ecosystems are challenging to study due to sampling difficulties.
The Yellowstone wolf-elk-aspen system is a classic example used to illustrate trophic cascades.
Previous studies may have been influenced by non-random sampling methods.

Discussion:

Non-random sampling of only tall, young aspen overestimated regeneration by 4-7 times compared to random sampling.
This bias occurred because the sampling method favored plants above elk browsing height and ignored non-regenerating stands.
Random sampling revealed a weaker trophic cascade than non-random methods, indicating a potential overstatement of effects.

Key Insights:

Sampling methodology critically impacts the interpretation of trophic cascades.
Wolf recovery in Yellowstone influences elk behavior and density, promoting aspen regeneration.
Accurate ecological understanding hinges on rigorous, unbiased sampling techniques.

Outlook:

Implementing random sampling is essential for reliable ecological research.
Re-evaluating existing data using robust sampling principles may refine our understanding of trophic cascades.
This study underscores the importance of methodological rigor in wildlife and ecosystem management.