Evaluation of a hierarchy of models reveals importance of substrate limitation for predicting carbon dioxide and methane exchange in restored wetlands

Abstract

Wetlands and flooded peatlands can sequester large amounts of carbon (C) and have high greenhouse gas mitigation potential. There is growing interest in financing wetland restoration using C markets; however, this requires careful accounting of both CO2 and CH4 exchange at the ecosystem scale. Here we present a new model, the PEPRMT model (Peatland Ecosystem Photosynthesis Respiration and Methane Transport), which consists of a hierarchy of biogeochemical models designed to estimate CO2 and CH4 exchange in restored managed wetlands. Empirical models using temperature and/or photosynthesis to predict respiration and CH4 production were contrasted with a more process‐based model that simulated substrate‐limited respiration and CH4 production using multiple carbon pools. Models were parameterized by using a model‐data fusion approach with multiple years of eddy covariance data collected in a recently restored wetland and a mature restored wetland. A third recently restored wetland site was used for model validation. During model validation, the process‐based model explained 70% of the variance in net ecosystem exchange of CO2 (NEE) and 50% of the variance in CH4 exchange. Not accounting for high respiration following restoration led to empirical models overestimating annual NEE by 33–51%. By employing a model‐data fusion approach we provide rigorous estimates of uncertainty in model predictions, accounting for uncertainty in data, model parameters, and model structure. The PEPRMT model is a valuable tool for understanding carbon cycling in restored wetlands and for application in carbon market‐funded wetland restoration, thereby advancing opportunity to counteract the vast degradation of wetlands and flooded peatlands.

Temporal Variation of Ecosystem Scale Methane Emission From a Boreal Fen in Relation to Temperature, Water Table Position, and Carbon Dioxide Fluxes

“…In such models the methane production typically depends on the available carbon pool development (Li et al, 2016;Oikawa et al, 2017;Raivonen et al, 2017;Tian et al, 2010;Walter & Heimann, 2000;Wania et al, 2010;Watts et al, 2013;Zhuang et al, 2004), in line with our findings. In such models the methane production typically depends on the available carbon pool development (Li et al, 2016;Oikawa et al, 2017;Raivonen et al, 2017;Tian et al, 2010;Walter & Heimann, 2000;Wania et al, 2010;Watts et al, 2013;Zhuang et al, 2004), in line with our findings.…”

Direct and Indirect Effects of Tides on Ecosystem‐Scale CO2 Exchange in a Brackish Tidal Marsh in Northern California

“…However, analyzing and interpreting continuous flux measurements can be challenging as carbon exchanges are complex, often involving nonlinear, asynchronous processes across diverse timescales that can be difficult to characterize using traditional statistical analysis (Sturtevant et al, ). Methods such as wavelet decomposition and information theory show promise for addressing these complexities by considering issues of scale, nonlinearity, and asynchrony directly (Sturtevant et al, ) and have been shown to improve accurate representation of carbon cycling in process models (Oikawa et al, ). Wavelets are a particular powerful technique to investigate scale in geophysical and ecological analysis (Cazelles et al, ; Torrence & Compo, ).…”

Soil properties and sediment accretion modulate methane fluxes from restored wetlands

“…A thorough understanding of CH 4 flux drivers is essential to these programs because the magnitude of CH 4 emissions may determine if restored wetlands are a GHG source or sink (Knox et al., ). These emissions could affect funding of wetland restoration programs if financed through C markets alone (Oikawa, Jenerette, et al., ), though wetlands provide a number of relevant ecosystem services, such as nutrient retention, protection from storms and sea‐level rise, and habitat preservation for wildlife (Hansson, Brönmark, Anders Nilsson, & Åbjörnsson, ; Swain, Boughton, Bohlen, & Lollis, ; Zedler & Kercher, ).…”