Quantitative analysis of the functional relationships existing between ecosystem components

Summary

For those systems which are amenable to tracer kinetic incorporation experiments it is possible to determine the pathways of nutrient flux throughout the system and to measure the steady state rates of intercomponent mass transfer through these pathways. In this paper a procedure is developed which allows one to employ incubation experiments to obtain the data required to analyse the flow of nutrients throughout the system. In such experiments a tracer is introduced via a single system component and the total radioactivities of the other system components are measured and recorded as functions of the time elapsed since the introduction of tracer. The resulting time-varying radioactivity curves can be successfully fitted to sums of exponentials by employing a particular mode of data point weighting. A specific mode of weighting the data points is required in typical incubation experiments if the component injected with label is large in comparison with the remaining components of the system. The exponential sums describing the time-varying radioactivities of the system components furnish the information required to determine and measure intercompartment nutrient fluxes; such determinations are made by assembling the coefficients and exponents appearing in the sums, into matrices, then employing a collineatory transformation. An illustrative example of the determination of intercomponent rates of mass transfer from data arising from a simulated incubation experiment is presented.