Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web
Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world's ecosystems are human dominated we broadened this dichotomy by considering...
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ftpubmed:oai:pubmedcentral.nih.gov:3648482 2023-05-15T15:51:06+02:00 Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web Muhly, Tyler B. Hebblewhite, Mark Paton, Dale Pitt, Justin A. Boyce, Mark S. Musiani, Marco 2013-05-08 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648482 http://www.ncbi.nlm.nih.gov/pubmed/23667705 https://doi.org/10.1371/journal.pone.0064311 en eng Public Library of Science http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648482 http://www.ncbi.nlm.nih.gov/pubmed/23667705 http://dx.doi.org/10.1371/journal.pone.0064311 This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. CC-BY Research Article Text 2013 ftpubmed https://doi.org/10.1371/journal.pone.0064311 2013-09-04T23:29:54Z Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world's ecosystems are human dominated we broadened this dichotomy by considering human effects in a terrestrial food-web. We studied a multiple human-use landscape in southwest Alberta, Canada, as opposed to protected areas where previous terrestrial food-web studies have been conducted. We used structural equation models (SEMs) to assess the strength and direction of relationships between the density and distribution of: (1) humans, measured using a density index; (2) wolves (Canis lupus), elk (Cervus elpahus) and domestic cattle (Bos taurus), measured using resource selection functions, and; (3) forage quality, quantity and utilization (measured at vegetation sampling plots). Relationships were evaluated by taking advantage of temporal and spatial variation in human density, including day versus night, and two landscapes with the highest and lowest human density in the study area. Here we show that forage-mediated effects of humans had primacy over predator-mediated effects in the food web. In our parsimonious SEM, occurrence of humans was most correlated with occurrence of forage (β = 0.637, p<0.0001). Elk and cattle distribution were correlated with forage (elk day: β = 0.400, p<0.0001; elk night: β = 0.369, p<0.0001; cattle day: β = 0.403, p<0.0001; cattle, night: β = 0.436, p<0.0001), and the distribution of elk or cattle and wolves were positively correlated during daytime (elk: β = 0.293, p <0.0001, cattle: β = 0.303, p<0.0001) and nighttime (elk: β = 0.460, p<0.0001, cattle: β = 0.482, p<0.0001). Our results contrast with research conducted in protected areas that suggested human effects in the food web are primarily predator-mediated. Instead, human influence on vegetation may strengthen bottom-up predominance and weaken top-down trophic cascades in ecosystems. We ... Text Canis lupus PubMed Central (PMC) Canada PLoS ONE 8 5 e64311 |
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Research Article Muhly, Tyler B. Hebblewhite, Mark Paton, Dale Pitt, Justin A. Boyce, Mark S. Musiani, Marco Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
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Research Article |
description |
Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world's ecosystems are human dominated we broadened this dichotomy by considering human effects in a terrestrial food-web. We studied a multiple human-use landscape in southwest Alberta, Canada, as opposed to protected areas where previous terrestrial food-web studies have been conducted. We used structural equation models (SEMs) to assess the strength and direction of relationships between the density and distribution of: (1) humans, measured using a density index; (2) wolves (Canis lupus), elk (Cervus elpahus) and domestic cattle (Bos taurus), measured using resource selection functions, and; (3) forage quality, quantity and utilization (measured at vegetation sampling plots). Relationships were evaluated by taking advantage of temporal and spatial variation in human density, including day versus night, and two landscapes with the highest and lowest human density in the study area. Here we show that forage-mediated effects of humans had primacy over predator-mediated effects in the food web. In our parsimonious SEM, occurrence of humans was most correlated with occurrence of forage (β = 0.637, p<0.0001). Elk and cattle distribution were correlated with forage (elk day: β = 0.400, p<0.0001; elk night: β = 0.369, p<0.0001; cattle day: β = 0.403, p<0.0001; cattle, night: β = 0.436, p<0.0001), and the distribution of elk or cattle and wolves were positively correlated during daytime (elk: β = 0.293, p <0.0001, cattle: β = 0.303, p<0.0001) and nighttime (elk: β = 0.460, p<0.0001, cattle: β = 0.482, p<0.0001). Our results contrast with research conducted in protected areas that suggested human effects in the food web are primarily predator-mediated. Instead, human influence on vegetation may strengthen bottom-up predominance and weaken top-down trophic cascades in ecosystems. We ... |
format |
Text |
author |
Muhly, Tyler B. Hebblewhite, Mark Paton, Dale Pitt, Justin A. Boyce, Mark S. Musiani, Marco |
author_facet |
Muhly, Tyler B. Hebblewhite, Mark Paton, Dale Pitt, Justin A. Boyce, Mark S. Musiani, Marco |
author_sort |
Muhly, Tyler B. |
title |
Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
title_short |
Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
title_full |
Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
title_fullStr |
Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
title_full_unstemmed |
Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web |
title_sort |
humans strengthen bottom-up effects and weaken trophic cascades in a terrestrial food web |
publisher |
Public Library of Science |
publishDate |
2013 |
url |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648482 http://www.ncbi.nlm.nih.gov/pubmed/23667705 https://doi.org/10.1371/journal.pone.0064311 |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Canis lupus |
genre_facet |
Canis lupus |
op_relation |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648482 http://www.ncbi.nlm.nih.gov/pubmed/23667705 http://dx.doi.org/10.1371/journal.pone.0064311 |
op_rights |
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1371/journal.pone.0064311 |
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PLoS ONE |
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8 |
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e64311 |
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