Effects of fertilization and seasonality on phosphorus pools in an ombrotrophic bog
Bibliographic record
Abstract
Nutrient cycling and nutrient status control primary productivity, decomposition, plant community composition, and microbial community composition in ombrotrophic bogs. Ombrotrophic bogs in Canada are often nitrogen and phosphorus co-limited, meaning that changes in phosphorus concentrations have dramatic effects on ombrotrophic bog ecology. To study the current state of biotic phosphorus cycling, I measured microbial and labile phosphorus concentrations in Mer Bleue Bog near Ottawa, ON over a period of 14 months. Both microbial and labile phosphorus concentrations varied greatly through the year. This variation is linked to changes in water table depth and season. High water tables were associated with higher microbial phosphorus concentrations, while low water tables were associated with lower microbial phosphorus concentrations, even in layers that remained saturated during the entire year. During a year with a mild winter, microbial phosphorus concentrations were high during late winter and during spring snowmelt, averaging 115 to 130 mg kg-1 P in layers above the water table. Microbial phosphorus concentrations then declined through the growing season as plants became more competitive, averaging 45 to 105 mg kg-1 P in layers above the water table. Labile phosphorus concentrations were often low, averaging 2 to 12 mg kg-1 P, but increased sharply to 45 mg kg-1 P in the upper layers of peat for short periods of time before being taken up by microorganisms and plants. Both microbial and labile phosphorus concentrations were highest near the surface and decreased with depth from 0 to 75 cm. To study the effects of nutrient addition and nutrient limitation on peatland soil phosphorus pools, samples were taken from the long-term fertilization experiment at Mer Bleue Bog. Samples were taken in 2021 following nearly twenty years of fertilizer application. These samples were subjected to a Hedley sequential fractionation to extract phosphorus along a chemical gradient of biological availability. In unfertilized peat, phosphorus concentrations were highest in the available and highly recalcitrant pools, with little between them. This U-shaped distribution of phosphorus along the gradient of availability contrasts with established patterns in mineral soils. In plots which received PK and NPK fertilizers, concentrations of both available phosphorus and highly recalcitrant phosphorus doubled. In plots receiving N fertilization alone, available and total P concentrations decreased, which may indicate increased demand for P by plants and microorganisms when N status is high. In all plots receiving fertilizer, concentrations of highly recalcitrant phosphorus increased, which may indicate increased decomposition of peat. In addition, fertilization led to changes aboveground. Chamaedaphne calyculata leaves in plots receiving PK and NPK were enriched in phosphorus compared to C. calyculata leaves in unfertilized plots and plots receiving N alone
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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".