Rapid soil formation and carbon accumulation along a Little Ice Age soil chronosequence in southeast Alaska
Bibliographic record
Abstract
• Spodosols developed within approximately 200 years. • Organic carbon accumulates rapidly following glacier retreat. • Subsurface SOC stocks became more abundant than surficial stocks after 155 years. • Subsurface C accumulation rates increased after soils exhibited spodic properties. • The formation of Fe oxyhydroxides was positively correlated with soil age. This study aims to assess the co-evolution of soil development and soil organic carbon (SOC) accumulation along a postglacial soil chronosequence in southeast Alaska. We hypothesize that in the early stages of soil development, larger SOC stocks are primarily found in surficial soil horizons and gradually become more abundant in subsurface horizons over time. Seven moraines were dated using dendrochronology, yielding ages of 73, 82, 89, 128, 155, 207, and 247 years. SOC and pedogenic Fe oxyhydroxide values from mature Spodosols, sampled outside the chronosequence, were used as a reference for the steady state of Spodosols in the region. From 73 to 128 years, soils were classified as Typic Cryorthents; by 155 years, as Spodic Dystrocryepts; and as Typic Haplocryods in the older moraines. A shift in SOC accumulation rates and depth distribution occurred once spodic properties developed. During the Entisol phase, most SOC stocks were concentrated in surficial horizons. After meeting spodic criteria, there was a shift toward subsurface mineral horizons, hosting over 50 % of SOC stocks. This shift in SOC depth distribution was supported by a significant positive relationship between subsurface SOC stocks and age, but not with surficial SOC stocks. Similarly, surficial SOC accumulation rates were elevated during early pedogenesis (e.g., 0.26 Mg C ha -1 yr −1 ), while subsurface SOC accumulation was lower (0.04 Mg C ha -1 yr −1 ), increasing to 0.19 Mg C ha -1 yr −1 once spodic properties were met. A significant positive correlation between pedogenic Fe and age highlights the role of SOC in enhancing the weathering of Fe-bearing minerals. Our findings support the hypothesis that subsurface SOC stocks rapidly become dominant over time with Spodosol development. This study underscores the consequences of glacier retreat on a portion of the terrestrial ecosystem, with direct impacts on carbon cycling.
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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 | 0.000 |
| 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".