The functional role of earthworms in carbon and nitrogen dynamics in riparian areas under different land use in Southern Québec
Notice bibliographique
Résumé
Riparian areas are located at the interface between terrestrial and aquatic ecosystems. Hydrological events and vegetation patterns drive decomposition and nutrient cycling occurring in these areas, ultimately determining whether riparian areas are a carbon (C) and nitrogen (N) sink or source to the environment. Earthworms play a central role in decomposition and nutrient cycling by fragmenting plant material and interacting with soil microorganisms. During this process, earthworms are assumed to increase CO2 and N2O production and fluxes, while increasing soluble compounds such as dissolved organic C and mineral N that may either be substrates for microbial activity and plants (i.e., plant N uptake) or lost from soil when leached through earthworm burrows (macropores). The objective of this research was to describe the earthworm community inhabiting riparian areas along the Pike River in southern Québec, identify the environmental factors driving earthworm community assemblage, and determine how earthworms in this area affected C and N dynamics under different land use. A field study of earthworms, soil, and vegetation showed that earthworm communities were larger (p <.0001) and more diverse in riparian sites compared to upland sites that cultivated with crops. Canonical correspondence analysis showed that soil moisture, vegetation, microbial biomass carbon (MBC) and soil parameters including ammonium (NH4) and phosphorus (P) were the main factors driving the separation of earthworm assemblages and associated plots (p < .005). A 5-month long microcosm experiment tested the effect of two earthworm species from riparian areas, the anecic Lumbricus terrestris and endogeic Aporrectodea turgida, on C and N losses from riparian soils via their effect on litter decomposition. Litter consisted of soybean residue (Glycine max), deciduous forest mix (Acer saccharum, Fagus grandifolia, Betula alleghaniensis) and reed canarygrass (Phalaris arundinacea). Earthworms increased CO2 and N2O losses from microcosms with soybean litter, by 14% (p < .0001) and 700% (p < .0001), respectively, but reduced CO2 and N2O losses by 18% (p < .0001) and 250% (p < .0001), respectively, when fed with reed canarygrass. The amount of soluble C and N in leachate and soil extracts depended on the interaction between earthworm species and litter type. Microcosms with earthworms increased gaseous C and N losses relative to soluble losses compared to microcosms without earthworms. The effect of earthworm presence and soil moisture on methanogenic and methanotrophic activity was tested in another laboratory microcosm experiment lasting 24 hours. Earthworm presence increased cumulative gross CH4 production from 365 μg CH4 g-1 d-1 soil (without earthworms) to 509 μg CH4 g-1 d-1 soil. Cumulative net CH4 consumption in soils with earthworms was 489 μg CH4 g-1 d-1, whereas in soils without earthworms it was 318 μg CH4 g-1 d-1. A field experiment in riparian areas along the Pike River tested the effects of manipulated earthworm populations on gas (CO2, N2O, and CH4) fluxes in spring. Throughout sites, mean CO2, CH4, and N2O fluxes ranged from 33.5 to 171.4 mg CO2-C, -44.2 and 3.1 μg CH4-C, and 1.2 to 51.6 μg N2O-N m-2 h-1, respectively. While soil moisture, vegetation cover, and earthworm variables were all correlated with CO2, N2O, and CH4 fluxes, only vegetation cover and soil moisture significantly predicted CO2 (R2=0.245, p = .0007) and N2O (R2=0.188, p = .0049) fluxes. Despite the important earthworm influence on C and N gas fluxes from riparian soils in the laboratory, it is not detectable at the field scale. I conclude that management of vegetation cover rather than earthworm populations would be a more effective way to minimize C and N gaseous and leachate losses in riparian areas in southern Québec.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 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) | 0,000 | 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 tête enseignante, 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 ».