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Apex Scavenger Declines Have Cascading Effects on Soil Biogeochemistry and Ecosystem Processes.
Torrey Stephenson1, David W Crowder2, Ernest Osburn3
1College of Agriculture and Life Sciences, University of Idaho, Moscow, Idaho, USA.
Global Change Biology
|September 25, 2025
Summary
Apex scavenger declines, like that of the Tasmanian devil (Sarcophilus harrisii), extend carcass persistence. This trophic downgrading significantly alters nutrient cycling and soil microbial communities, impacting ecosystem functions.
Area of Science:
- Ecology
- Environmental Science
- Biogeochemistry
Background:
- Apex scavengers play a crucial role in food web dynamics and ecosystem functions.
- Trophic downgrading, resulting from apex species decline, can have cascading effects on ecosystems.
- The impact of scavenger declines on nutrient cycling and soil microbial communities remains understudied.
Purpose of the Study:
- To investigate the consequences of Tasmanian devil (Sarcophilus harrisii) population declines on carcass persistence, nutrient cycling, and soil microbial communities.
- To assess the role of subordinate scavengers in compensating for the loss of apex scavengers.
- To explore seasonal and interkingdom interactions in carcass decomposition and nutrient flux.
Main Methods:
- Utilizing a disease-induced gradient in Tasmanian devil population densities.
- Manipulating carcass access and conducting experiments across summer and winter seasons.
- Quantifying carcass persistence, nutrient flux (e.g., ammonium), soil microbiome diversity, and microbial community composition.
Main Results:
- Tasmanian devil declines significantly increased carcass persistence and belowground nutrient flux (18-134-fold for ammonium).
- Increased nutrient availability reduced soil microbiome diversity (up to 26%) and increased relative abundance of zoonotic pathogens.
- Microbial communities shifted towards faster-growing taxa, with potential implications for carbon sequestration; winter conditions dampened these responses.
Conclusions:
- Apex scavenger declines have profound impacts on ecosystem functions, extending beyond food web dynamics to nutrient cycling and soil health.
- Subordinate scavengers cannot fully replace the functional role of apex scavengers.
- Trophic downgrading disrupts soil microbial communities, potentially increasing pathogen prevalence and altering biogeochemical processes.
Keywords:
carbon cyclingmicrobial ecologynutrient cyclingscavengerssoil biogeochemistrytrophic downgradingMore Related Videos
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