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A new method to reconstruct quantitative food webs and nutrient flows from isotope tracer addition experiments

Citation

Lopez-Sepulcre, Andres et al. (2020), A new method to reconstruct quantitative food webs and nutrient flows from isotope tracer addition experiments, Dryad, Dataset, https://doi.org/10.5061/dryad.8sf7m0chx

Abstract

Understanding how nutrients flow through food webs is central in ecosystem ecology. Tracer addition experiments are powerful tools to reconstruct nutrient flows by adding an isotopically enriched element into an ecosystem, and tracking its fate through time. Historically, the design and analysis of tracer studies have varied widely, ranging from descriptive studies to modeling approaches of varying complexity. Increasingly, isotope tracer data is being used being used to compare ecosystems and analyze experimental manipulations. Currently, a formal statistical framework for analyzing such experiments is lacking, making it impossible to calculate the estimation errors associated with the model fit, the interdependence of compartments, or the uncertainty in the diet of consumers. In this paper we develop a method based on Bayesian Hidden Markov Models, and apply it to the analysis of $^{15}$N-NH$_4^+$ tracer additions in two Trinidadian streams in which light was experimentally manipulated. Through this case study, we illustrate how to estimate N fluxes between ecosystem compartments, turnover rates of N within those compartments and the associated uncertainty. We also show how the method can be used to compare alternative models of food web structure, calculate the error arround derived parameters, and make statistical comparisons between sites or treatments.

Funding

Academy of Finland, Award: 29594

National Science Foundation

National Science Foundation, Award: EF062363