Soil organic carbon and <sup>13</sup>C changes when annual crops are replaced with perennial biomass crops in southwestern Ontario, Canada
Bibliographic record
Abstract
Switchgrass ( Panicum virgatum) and miscanthus ( Miscanthus spp.) are C4 perennial biomass crops (PBCs) commonly cultivated in Ontario. The 13C natural abundance technique was used to assess the following: (i) quantify the proportion of C4-derived soil organic carbon (SOC) stock (Mg C ha−1) within the SOC stocks of the whole soil, (ii) determine the C4-derived SOC sequestration rate, and (iii) quantify C4-derived SOC stocks in soil particle size fractions. This was achieved by analyzing the δ13C values in SOC of both the whole soil and various soil particle size fractions in PBC fields that were converted from agriculture. At Guelph after 11 years of PBC, C4-derived SOC stock as a proportion of SOC stock in the whole soil accounted for 30% in switchgrass and 31% in miscanthus fields, while at Elora it comprised 41% in switchgrass and 50% in miscanthus. However, in Burlington after 4 years, C4-derived SOC represented 10%–12% in PBC fields compared to 17% in agriculture fields. The C4-derived SOC sequestration rates were 0.8, 0.7, and 0.4 Mg C ha−1 year−1 in switchgrass, miscanthus, and agriculture fields, respectively at the Guelph site. In miscanthus fields, lower C4-derived SOC stock in macro soil particles were observed, yet higher percentages were observed in micro soil particles and the silt plus clay fractions compared to switchgrass and agriculture fields. Agriculture fields had higher C4-derived SOC in macro soil particles, indicating lower SOC stability. Therefore, cultivating PBCs on low-productive agricultural lands could contribute to climate change mitigation practices due to increased SOC stability.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".