Stand Age and Productivity Control Soil Carbon Dioxide Efflux and Organic Carbon Dynamics in Poplar Plantations
Bibliographic record
Abstract
Establishment of hybrid poplar (HP) plantations has been advocated as an effective method for sequestering CO2 from the atmosphere. However, how carbon (C) cycling in HP plantations changes during stand development under different soil fertility and climatic conditions is poorly understood. We studied the dynamics of soil respiration (Rs) and its heterotrophic (Rh) and autotrophic (Ra) components and soil organic C (SOC) content in HP plantations of different stand ages established on soils with different productivity (Class 1 vs. Class 3 soils) in Alberta (AB) and Ontario (ON), Canada. The Rs was the highest for AB-Class 1 (high-productivity) soils, followed by AB-Class 3 and ON-Class 3 (low-productivity) soils. Annual Rs, Rh, and Rh/Rs decreased in the first 3 yr in AB-Class 1 and 6 yr in AB-Class 3 soils after plantation establishment and increased thereafter, but they increased with stand age after plantation establishment in ON-Class 3 soils. The SOC content in the AB-Class 1, AB-Class 3, and ON-Class 3 sites decreased in the first 3, 5, and 1.5 yr, respectively, after plantation establishment and then increased, reaching the pre-establishment level after 6, 10, and 3 yr, respectively. From this first attempt to understand C cycling across multiple sites with different soil fertility levels, we conclude that stand age and soil productivity play a significant role in affecting C cycling, and such effects should be considered in regional and global C cycling models, especially when assessing the C sequestration potential of HP plantations.
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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 | 0.000 | 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 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".