Impacts of soil accumulation from erosion on greenhouse gas production and emission from soil within a complex and cultivated landscape
Notice bibliographique
Résumé
In cultivated, topographically complex landscapes, soil erosion results in the redistribution of large amounts of soil.This soil redistribution changes the source materials and related soil properties within landscapes and within soil profile.These changes are expected to affect production and emission of greenhouse gases (GHG).To evaluate the effect of soil accumulation on CO2 and, N2O production and emission, two laboratory experiments and one fierd experiment were carried out.The column study was f,trst conducted in a growth chamber to study the relatio¡ship between soil depth and GHG emission.Results showed soil depth had a great effect on CO2 flux.Co2 flux increased drarnatically with soil depth.Regression analysis of data collected over 70 days showed the relationship between cumulative flux and soil depth can be described using a linear regression.However, as soil depth increased, emissions are not expected to increase proportionally.The effect of soil depth on N2O flux was observed as well.Generally, N2o flux increased with soil depth.Regressio¡ analysis of data collected over 70 days showed the cumulative flux also increased lìnearly.This experiment was lirnited in ability to determine the exact effect of soil depth due to lirnited numbers of depth treatments and the single replicate.Based on the preliminary results of the column study, a detailed field experiment was conducted to study the effect of soil accumulation from soil erosion on GHG profile concentrations and surface emissions.This study was carried out in three depressions within a complex, cultivated landscape, 17 krn north of Brandon, Manitoba.Results showed COz flux and profrle concentrations had obvious seasonal patterns.Co2 flux and concentration changed dramatically as air and soil temperature varied, indicati¡g that temperature is the key factor controlling greenhouse gas production and ernission.The highest variation in COz concentration occurred during the growing season.Higher CO2 concentration occurred at the greater depth in these depressions, probably resulting frorn high production and low diffusion rates.A thicker A horizon due to soil accumulation, root respiration, and microbial respiration resulted in higher CO2 production.The high water table level and poor drainage in the depressions limited gas diffusion to the aboveground atmosphere as well.Significant soil accumulation was observed in each of the three depressions.The soil accumulation favored CO2 production in that it increased quantities of soil organic carbon and nitrogen in the soil surface.However, the effect of soil accumulation on CO2 flux was different in the three depressions due to soil moisture conditions.Results also showed N2O profile concentrations and surface flux had significant seasonal patterns as well.High N2O flux and profile concentrations only occurred during spring thaw periods.High soil moisture and available carbon and nitrogen during spring thaw periods rnight have contributed to the high production rates.Although soil accumulation enriched organic carbon and nitrogen in the soil prof,rles, the effect of soil accurnulation on N2O production and emission only occurred during the spring thaw events.The thickened A horizon increased N2O production in soil profiles.However, this accurnulation may have decreased N2O emission due to the limited diffusion in the soil resulting in the conversion of NzO to N2.Thus, the effect of soil depositio' from erosion on N2O emission was cornplicated by hydrologic and pedologic co¡ditions.The potential production of CO2 and N2O at different soil depths from the field site was further studied with a microcosm experiment.This study revealed the potential gas production decreased with increased soil depth for both CO2 and N2O.The surface 25 cm of soil appeared to be the major potential source in COz and N2O production, in that this lIt layer was found to be rich in organic carbon and nitrogen, favoring microbial activity and mìcrobial biomass.Therefore, the accumulation of soil on the surface rich in organic carbon should increase COz and N2O production within the soil profile, at least in the short-tenn.In summary, the effect of the soil accumulation on GHG production and emission was complex.Its effect on CO2 and N2O flux was soil environment-specific. Soil accunulation increased GHG production in that it thickens the surface soil with high available carbon and nitrogen.However, this accumulation may have decreased COz and N2O emission due to the limited diffusion in the soil resulting in the further conversion of N2O to Nz.The effect of soil deposition also could affect GHG flux through its effect on soil moisture, temperature and substrate availability.
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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 | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| 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 ».