The functional role of earthworms in carbon and nitrogen dynamics in riparian areas under different land use in Southern Québec
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".