Resource competition model predicts zonation and increasing nutrient use efficiency along a wetland salinity gradient

Ecology
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Abstract

A trade-off between competitive ability and stress tolerance has been hypothesized and empirically supported to explain the zonation of species across stress gradients for a number of systems. Since stress often reduces plant productivity, one might expect a pattern of decreasing productivity across the zones of the stress gradient. However, this pattern is often not observed in coastal wetlands that show patterns of zonation along a salinity gradient. To address the potentially complex relationship between stress, zonation, and productivity in coastal wetlands, we developed a model of plant biomass as a function of resource competition and salinity stress. Analysis of the model confirms the conventional wisdom that a trade-off between competitive ability and stress tolerance is a necessary condition for zonation. It also suggests that a negative relationship between salinity and production can be overcome if (1) the supply of the limiting resource increases with greater salinity stress or (2) nutrient use efficiency increases with increasing salinity. We fit the equilibrium solution of the dynamic model to data from Louisiana coastal wetlands to test its ability to explain patterns of production across the landscape gradient and derive predictions that could be tested with independent data. We found support for a number of the model predictions, including patterns of decreasing competitive ability and increasing nutrient use efficiency across a gradient from freshwater to saline wetlands. In addition to providing a quantitative framework to support the mechanistic hypotheses of zonation, these results suggest that this simple model is a useful platform to further build upon, simulate and test mechanistic hypotheses of more complex patterns and phenomena in coastal wetlands.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Resource competition model predicts zonation and increasing nutrient use efficiency along a wetland salinity gradient
Series title Ecology
DOI 10.1002/ecy.2131
Volume 99
Issue 3
Year Published 2018
Language English
Publisher Ecological Society of America
Contributing office(s) Wetland and Aquatic Research Center
Description 11 p.
First page 670
Last page 680
Country United States
State Louisiana