Impacts of earthworm invasion on soils of the Canadian boreal forest
Bibliographic record
Abstract
Exotic species of earthworms are invading North American forests, where native earthworms were extirpated by the last glaciation. The invasion of these ecosystem engineers can alter soil organic matter (SOM) dynamics, carbon (C) persistence, and ecosystem functioning. While the topic has been widely studied in temperate forests, the understanding of the consequences of this invasion in boreal forests is still insufficient. I aimed to determine how invasive earthworms are affecting boreal forest soils, their C stocks, SOM dynamics, and associated microbial communities. To ad-dress these objectives, I selected sites to encompass the three most common soil types across the Canadian boreal forest habitable by earthworms: Luvisols, Podzols, and Brunisols. Within each site, sampling zones were delimited to only differ by invasion status while keeping other environ-mental and pedological factors as similar as possible. I described soil morphological features and estimated the C stocks for the forest floors and mineral soils of invaded and non-invaded soils. I then compared their bacterial and fungal communities using phospholipid fatty acid (PLFA) analysis and metabarcoding of the 16S rRNA gene and ITS2 region. Finally, I estimated the labile (i.e. mineralizable) C using laboratory incubations, characterized the chemical composition of SOM by pyrolysis-gas chromatography-mass spectrometry, and determined C distribution in different density and size fractions of the mineral soil. The presence of invasive geoengineering earthworms resulted in the thinning of forest floors and the development of novel Ahu horizons, enriched in C and clay. For the forest floors, there was a net loss of C stocks, although the proportion of labile C remained unchanged. While fungal com-munities of forest floors were unaffected by earthworm invasion, their bacterial communities did shift, notably with increased Gram(+):Gram(-) bacteria ratios, suggesting decreased C availability. In the novel Ahu horizons, the proportion of labile C was higher than in non-invaded mineral soils and C content was significantly higher across all < 2 mm soil fractions, with a greater proportion of C found in the occluded light fraction. The proportion of root-derived SOM, identified from suberin markers, decreased after earthworm invasion, while that of microbially degraded SOM increased. Increased microbial decomposition was further supported by higher C oxidation states observed in earthworm-invaded soils, and increased C content of the silt and clay-sized fractions, predominantly containing microbially degraded C. In mineral soils, earthworm invasion favoured fungi over bacteria, mainly by an increased relative abundance of ectomycorrhizal fungi at the expense of saprotrophic fungi. For bacterial communities, increased Proteobacteria:Acidobacteriota and decreased Gram(+):Gram(-) bacteria ratios indicated higher nutrient availability in earth-worm-invaded mineral soils. These findings show that earthworm invasion significantly affects C dynamics and microbial communities in boreal forest soils, notably through a faster degradation of fresh SOM. This could alter C sequestration and other ecosystem services of boreal forests in the long term.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".