Understanding winter carbon dynamics in peatlands with new data sources

By: Katie Hettinga

Even in the quiet of winter (Figure 1), microorganisms are hard at work in peatlands, cycling nutrients such as carbon. As a result, during winter, peatlands tend to release carbon dioxide (CO₂) through microbial respiration because the plants that absorb CO₂ are dormant. In contrast, plants take in CO₂, via photosynthesis, during the growing season (GS). These seasonal dynamics generally balance out, with peatlands acting as net CO₂ sinks over the course of the year. In Canada, however, winter temperatures are rising faster than other seasons. Warmer winters result in shorter cold periods and longer GSs. While a longer GS may increase the amount of CO₂ peatlands absorb, the warmer conditions could also boost microbial activity, potentially offsetting the extra CO₂ absorbed by plants. This shift in seasonal dynamics could tip the balance and weaken the ability of peatlands to act as carbon sinks. Understanding these seasonal changes is crucial for predicting how peatlands will respond to a changing climate and provide insights into their potential role as nature-based solutions. 

The Challenge of Gathering Data in Winter 

Collecting continuous field data in peatlands is already difficult in summer because of the demanding terrain, and the need to bring along heavy equipment. In winter, these challenges are magnified. Setting up and maintaining field equipment in winter presents additional obstacles, including: 

• Freezing temperatures which can cause equipment failures 

• Shorter daylight hours limiting solar power supply 

• Icy conditions making it hard to access and repair equipment 

As a result, winter data is often underrepresented. Even near-continuous monitoring equipment struggles in such conditions, leading to large data gaps for the season. 

Overcoming the Challenges 

To address these challenges, part of my work focuses on how remotely sensed and modeled data can supplement field data and improve our understanding of the winter (otherwise referred to as the Non-Growing Season (NGS)) CO₂ fluxes. Our research on NGS contributions to the annual net CO₂ budget in Canadian peatlands analyzes observations from five sites located across three ecoclimate zones. This work aims to: 

• Evaluate how well remotely sensed and modeled data match field data 

• Compare the net CO₂ budget of the GS to that of the NGS 

• Assess how the length of the GS and NGS influences net annual CO₂ budgets  

Preliminary Findings 

Our initial results suggest: 

• Field data tends to show a weaker CO₂ sink during the GS and a stronger CO₂ source during the NGS compared to remotely sensed and modeled data 

• The relationship between NGS emissions and GS uptake varies substantially between sites and years 

• Longer GS periods led to increased CO₂ uptake at the study sites 

These preliminary results will continue to be explored as part of the Can-Peat project, where we aim to assess the regional vulnerability and resilience of peatland carbon stocks. 

For more information, please visit the Can-Peat website.