Carbon cycling at a post-extraction restored peatland: Small-scale processes to global climate impacts
Notice bibliographique
Résumé
Peatlands store large amounts of organic carbon (C) and are an important component of the global climate system. Climate and peatland land surfaces are closely coupled through land-atmosphere exchanges of greenhouse gases (GHG), such as carbon dioxide (CO2) and methane (CH4). When undisturbed, peatlands exert a long-term (millennia) negative radiative GHG forcing (climate cooling) through CO2 removal from the atmosphere, and a short-term (decades) positive forcing (climate warming) with the addition of CH4 to the atmosphere. Peatland drainage and extraction, however, results in mineralization of stored peat, releasing large amounts of CO2 while generally reducing CH4 to minimal levels. Rewetting and actively restoring vegetation is now a restoration approach used to reduce CO2 emissions from degraded peatlands. However, the timeframe needed for restoration to re-establish the C sink function of an undisturbed peatland remains poorly constrained due to a lack of multi-year measurements. In this thesis, I analyze three years of eddy covariance flux measurements from a post-extraction restored peatland in eastern Quebec, Canada that was restored 14 years prior. I link these measurements with flux footprint modelling, stable isotope fractionation data and pore water concentrations to characterize how belowground C cycling and fluxes are impacted by restoration. I combine a series of flux towers at post-extraction unrestored and restored peatlands in eastern and western Canada with an atmospheric perturbation model to further reveal how after-use management is affecting the global climate.The post-extraction restored peatland was a C sink of 78 ± 17 g C m-2 yr-1 within fourteen years of restoration, due to strong CO2 uptake and small CH4 emission and dissolved organic carbon export. A comparison with an undisturbed reference peatland (Mer Bleue) revealed annual NEE at the restored peatland was most similar to wetter, more productive years at the reference peatland. A mapping of post-extraction (1980 onwards) canopy structure changes showed broad comparability between the restored peatland and surrounding intact peatland within five years of restoration. The enhanced vegetation index results suggest that the developing vegetation in general had a normal response to environmental factors and was not experiencing any enduring stress from the underlying cutover peat. While the processes behind the surface net CO2 flux appear successfully recovered, approximately two thirds of the restored peatland was a minimal source of CH4, suggesting a lag in the recovery of belowground C cycling processes. Carbon turnover in the cutover peat beneath the new Sphagnum layer was slow and appeared to occur only with E. vaginatum substrate input and plant-mediated transport. The C isotopic fractionation factor for CH4 and CO2 in the restored field pore water exhibited a dominance of acetoclastic methane production, even deeper in the cutover peat profile. In contrast, isotopic fractionation in the former drainage ditches showed a balance of acetoclastic and hydrogenotrophic methanogenesis deeper in the profile, indicating that some bulk peat C turnover was occurring. Over time (decades), C turnover of the new peat is expected to limit the impacts of the cutover peat on the surface CH4 flux.Flux measurements at unrestored sites in eastern and western Canada reveal that not restoring post-extraction peatlands leads to decades of CO2 addition to the atmosphere, with low CH4 emission. The after-use decision to not restore results in a positive radiative forcing seven times more powerful than the negative forcing achieved by active restoration after 500 years. Prompt active restoration achieves a neutral climate impact about 155 years earlier than restoration after a 20-year delay. In contrast, IPCC Tier 1 emission factors based on a wide range of rewetting activities display a continually positive radiative forcing, even with prompt rewetting
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».