A hotspot of CH4 emission in a Danish agricultural soil: A soft spot in our knowledge?
Notice bibliographique
Résumé
Danish agricultural ecosystems are one of the main contributors to the total anthropogenic emissions of greenhouse gases in Denmark. The main research focus on greenhouse gas emissions from mineral agricultural soils has been on N2O, and on how the N2O emissions respond to fertilizer addition and different agricultural practices. Studies on CH4 fluxes are scarce and mostly show a small uptake of CH4, indicating that oxidation of CH4 is dominant in agricultural soils. As part of the NATEF (National emission factors for nitrous oxide from nitrogen fertilizers and crop rotations) project, we have established a field experiment in Taastrup, Denmark. The experiment has been running since early 2019, and consists of 12 plots (4 rotation treatments × 3 blocks) that each are managed following a common Danish crop rotation (main crops: spring barley, winter wheat and oilseed rape) in addition to cover crops (oat, phacelia, oilseed radish) following winter wheat. The field experiment is one of four identical field experiments located across Denmark, thereby capturing the variation in climate and soil types seen in Denmark. The main aim of the project is to determine emission factors for nitrous oxide for Danish cropping systems. This is achieved by regular manual measurements of N2O, CH4 and CO2 fluxes by the discrete closed chamber method in all plots. Furthermore, we have deployed an automated flux chamber system (ECO2 FluX, Prenart Equipment) connected to a greenhouse gas analyzer (G2508, Picarro) to provide high-frequency measurements of the fluxes of N2O, CH4 and CO2. In each growing season, two plots were selected and three automated chambers were placed in each plot, totaling six automated chambers in the study. The automated measurements allowed us to examine the high-frequency temporal dynamics in the fluxes, e.g. periods following rain events, freeze-thaw, fertilization or tilling. As expected, we generally observed emissions of N2O across all plots with different crops. CH4 fluxes were slightly negative (i.e. uptake) or close to zero during most periods, indicating that oxidation was the dominant process. However, during the autumn of 2019, we captured CH4 emission by the automated chambers in the plot with oilseed radish, while at the same time, the automated chambers in a plot with winter wheat showed no CH4 emissions. However, spatial variation in emissions were very large indicating that edaphic and topological factors played a major role. Our results show evidence that hotspots of CH4 emissions can occur in Danish agricultural ecosystems that otherwise mostly act as a sink for CH4. We expect that similar hotspots for CH4 emissions could exist in other similar agricultural systems.
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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 | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,003 | 0,002 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,001 |
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 ».