TimeFRAME

A Bayesian Mixing Model to Unravel Isotopic Data and Quantify Trace Gas Production and Consumption Pathways for Timeseries Data

The recently developed FRAME (isotope FRactionation And Mixing Evaluation) interface is a much needed first step towards a robust community tool to quantify N₂O production and consumption pathways from isotopic data including clearly defined quantification of uncertainty (Lewicki et al., 2022). FRAME uses a Markov Chain Monte Carlo approach to simultaneously determine mixing between N₂O from different sources as well as the extent of reduction, with an estimate of uncertainty. This modelling approach has been designed and validated for identification of N₂O production pathways and quantification of N₂O reduction progress in soil incubation experiments. However, FRAME can currently only be applied to discrete datasets; analysis of mixing between pathways across a timeseries generated from a field or laboratory experiment is not possible, except by considering all time points as independent and thus losing timeseries information.

We developed TimeFRAME to address this problem, and implement FRAME with autocorrelation between points along a defined dimension, usually time. TimeFRAME was developed by Philipp Fischer for his MSc at ETHZ:

MasterThesis_PhilippFischer Download

Following on from Philipp’s MSc thesis, we conducted additional testing of TimeFRAME and released a code package and a manuscript describing its use. If you are using or would like to use TimeFRAME, we look forward to hearing about your experience, questions, comments, difficulties… please get in contact with us! We hope to continue improving and extending TimeFRAME in the coming years.

Comparison of TimeFRAME results with pathways estimates from a dual isotope plot approach. TimeFRAME was applied in two configurations, i) using only δ¹⁵N^SP and δ¹⁸O and Ni and bD pathways, and ii) using δ¹⁵N^bulk, δ¹⁵N^SP and δ¹⁸O with Ni, bD and fD pathways. The dual isotope approach used δ¹⁵N^SP and δ¹⁸O and Ni and bD pathways, in configurations MR (mixing then reduction) and RM (reduction then mixing). a) A 1:1 comparison of estimates from the two TimeFRAME configurations and the dual isotope plot MR and RM methods. b) A plot of the estimates for each pathway from the two TimeFRAME configurations and from the dual isotope MR method. See manuscript for details.