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Producer nutritional quality controls ecosystem trophic structure.

Cebrian J, Shurin JB, Borer ET, Cardinale BJ, Ngai JT, Smith MD, Fagan WF - PLoS ONE (2009)

Bottom Line: Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients.There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive.Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems.

View Article: PubMed Central - PubMed

Affiliation: Dauphin Island Sea Lab and Department of Marine Sciences, University of South Alabama, Dauphin Island, Alabama, United States of America. jcebrian@disl.org

ABSTRACT
Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients. There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive. Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems. By increasing the efficiency of trophic transfer, higher producer nutritional quality results in steeper ecosystem trophic structure, and those changes are more pronounced in terrestrial than in aquatic ecosystems probably due to the more stringent nutritional limitation of terrestrial herbivores. These results explain why ecosystems composed of highly nutritional primary producers feature high consumer productivity, fast energy recycling, and reduced carbon accumulation. Anthropogenic changes in producer nutritional quality, via changes in trophic structure, may alter the values and functions of ecosystems, and those alterations may be more important in terrestrial ecosystems.

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The ratio (mean±SD) of herbivore-to-producer biomass (H∶P, in g element m−2 ∶ g element m−2) in aquatic and terrestrial systems.Gray, white and black circles correspond to carbon, nitrogen and phosphorus units, respectively. Ratios were analyzed with a two way ANOVA with element (carbon, nitrogen and phosphorus) and system type as the two factors after log-transformation to comply with the assumptions of ANOVA. Ratios varied among elements (P<0.001) and also among system types (P<0.001). Most importantly, the differences among elements depended on the system type considered (P<0.05 for the interaction between element and system type) indicating that, for terrestrial systems, ratios expressed in carbon units tended to be lower than ratios expressed in nitrogen or phosphorus units, but not for aquatic systems.
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pone-0004929-g002: The ratio (mean±SD) of herbivore-to-producer biomass (H∶P, in g element m−2 ∶ g element m−2) in aquatic and terrestrial systems.Gray, white and black circles correspond to carbon, nitrogen and phosphorus units, respectively. Ratios were analyzed with a two way ANOVA with element (carbon, nitrogen and phosphorus) and system type as the two factors after log-transformation to comply with the assumptions of ANOVA. Ratios varied among elements (P<0.001) and also among system types (P<0.001). Most importantly, the differences among elements depended on the system type considered (P<0.05 for the interaction between element and system type) indicating that, for terrestrial systems, ratios expressed in carbon units tended to be lower than ratios expressed in nitrogen or phosphorus units, but not for aquatic systems.

Mentions: To offer further support for more severe nutritional limitation of herbivores in terrestrial than in aquatic ecosystems, we compared the ratio of herbivore-to-producer biomass expressed in units of carbon, nitrogen or phosphorus. Modeling and empirical studies suggest that herbivores that are more severely limited by the nutritional quality of their diet tend to retain nutrients in their bodies to a greater extent [19]–[22]. Thus, ratios of herbivore- to-producer biomass in terrestrial ecosystems should be higher when expressed in nitrogen or phosphorus units than when expressed in carbon units, whereas such differences should be less pronounced in aquatic ecosystems. We compiled values of body nutrient content (i.e., nitrogen or phosphorus as % body dry weight) for the herbivores in a subset of the studies compiled (Data Sets S1) and plotted the ratios of herbivore-to-producer biomass in units of carbon, nitrogen and phosphorus for diverse aquatic and terrestrial ecosystems (Fig. 2). As expected, ratios in terrestrial ecosystems tended to be higher in terms of nitrogen and phosphorus than carbon units, but this was not the case for aquatic ecosystems. This supports that terrestrial herbivores are more severely limited by the nutritional quality of their diet than aquatic herbivores.


Producer nutritional quality controls ecosystem trophic structure.

Cebrian J, Shurin JB, Borer ET, Cardinale BJ, Ngai JT, Smith MD, Fagan WF - PLoS ONE (2009)

The ratio (mean±SD) of herbivore-to-producer biomass (H∶P, in g element m−2 ∶ g element m−2) in aquatic and terrestrial systems.Gray, white and black circles correspond to carbon, nitrogen and phosphorus units, respectively. Ratios were analyzed with a two way ANOVA with element (carbon, nitrogen and phosphorus) and system type as the two factors after log-transformation to comply with the assumptions of ANOVA. Ratios varied among elements (P<0.001) and also among system types (P<0.001). Most importantly, the differences among elements depended on the system type considered (P<0.05 for the interaction between element and system type) indicating that, for terrestrial systems, ratios expressed in carbon units tended to be lower than ratios expressed in nitrogen or phosphorus units, but not for aquatic systems.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2654170&req=5

pone-0004929-g002: The ratio (mean±SD) of herbivore-to-producer biomass (H∶P, in g element m−2 ∶ g element m−2) in aquatic and terrestrial systems.Gray, white and black circles correspond to carbon, nitrogen and phosphorus units, respectively. Ratios were analyzed with a two way ANOVA with element (carbon, nitrogen and phosphorus) and system type as the two factors after log-transformation to comply with the assumptions of ANOVA. Ratios varied among elements (P<0.001) and also among system types (P<0.001). Most importantly, the differences among elements depended on the system type considered (P<0.05 for the interaction between element and system type) indicating that, for terrestrial systems, ratios expressed in carbon units tended to be lower than ratios expressed in nitrogen or phosphorus units, but not for aquatic systems.
Mentions: To offer further support for more severe nutritional limitation of herbivores in terrestrial than in aquatic ecosystems, we compared the ratio of herbivore-to-producer biomass expressed in units of carbon, nitrogen or phosphorus. Modeling and empirical studies suggest that herbivores that are more severely limited by the nutritional quality of their diet tend to retain nutrients in their bodies to a greater extent [19]–[22]. Thus, ratios of herbivore- to-producer biomass in terrestrial ecosystems should be higher when expressed in nitrogen or phosphorus units than when expressed in carbon units, whereas such differences should be less pronounced in aquatic ecosystems. We compiled values of body nutrient content (i.e., nitrogen or phosphorus as % body dry weight) for the herbivores in a subset of the studies compiled (Data Sets S1) and plotted the ratios of herbivore-to-producer biomass in units of carbon, nitrogen and phosphorus for diverse aquatic and terrestrial ecosystems (Fig. 2). As expected, ratios in terrestrial ecosystems tended to be higher in terms of nitrogen and phosphorus than carbon units, but this was not the case for aquatic ecosystems. This supports that terrestrial herbivores are more severely limited by the nutritional quality of their diet than aquatic herbivores.

Bottom Line: Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients.There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive.Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems.

View Article: PubMed Central - PubMed

Affiliation: Dauphin Island Sea Lab and Department of Marine Sciences, University of South Alabama, Dauphin Island, Alabama, United States of America. jcebrian@disl.org

ABSTRACT
Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients. There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive. Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems. By increasing the efficiency of trophic transfer, higher producer nutritional quality results in steeper ecosystem trophic structure, and those changes are more pronounced in terrestrial than in aquatic ecosystems probably due to the more stringent nutritional limitation of terrestrial herbivores. These results explain why ecosystems composed of highly nutritional primary producers feature high consumer productivity, fast energy recycling, and reduced carbon accumulation. Anthropogenic changes in producer nutritional quality, via changes in trophic structure, may alter the values and functions of ecosystems, and those alterations may be more important in terrestrial ecosystems.

Show MeSH
Related in: MedlinePlus