Belowground plant material and its contribution to soil volume in a St. Lawrence salt marsh, QC, Canada
Bibliographic record
Abstract
Accumulation of belowground plant material (live roots, rhizomes, and dead material) is critical to vertical accretion of tidal salt marsh soils and their ability to maintain elevation with respect to sea-level rise. Many studies utilize a single, global relationship between soil organic carbon and belowground volume, which does not include the pore space created by belowground growth, thus does not appropriately reflect the contribution of vegetation to soil accretion. This thesis reports on research that seeks to address this gap.Chapter 1 is an introduction and literature review that describes tidal marshes vegetation typical of Northwest Atlantic tidal salt marshes. This chapter describes the importance of living biomass (roots and rhizomes) and dead material of the dominant marsh species in soil vertical accretion for marsh resiliency to keep up with sea-level changes.Chapter 2 is written in manuscript style including methods and results of a study of the relationship of the volume of live roots and rhizomes to their dry biomass. The study focuses on four species in a Quebec salt marsh. The species, Spartina alterniflora, Spartina patens, and invasive Phragmites australis were identified in the aboveground growth, while only tubers and roots of Cyperus esculentus were found. Cores of the top 30 cm of soil were collected and cut into 0-15 and 15-30 cm sections from the S. alterniflora –dominated low marsh, the S. patens–dominated high marsh, and the upper S. patens marsh invaded by P. australis. The soil was washed over a 1 mm sieve, and the organic matter was retained. The live material was sorted into fractions of roots and rhizomes by species. The volume of all components was measured by displacement in water before drying to obtain mass. An overall conversion factor of 8.2 g cm-3 reflects the volumetric contribution of live roots, rhizomes, and organic matter (OM) of all species studied. The relationship varies by species, with S. alterniflora contributing the greatest volume per unit mass (8.9 g cm-3), followed by S. patens (7.9 g cm-3), then P. australis and C. esculentus, both at 5.6 g cm-3. The results of this thesis not only demonstrate that the total mass and volume of each species for each component (rhizomes, roots, and dead material) are strongly correlated but that measurements of simple carbon density underestimate the actual contribution of salt marsh plants to the soil volume.Chapter 3 presents final conclusions, limitations of the study reported on in Chapter 2, and identifies directions that would be valuable for future research
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".