Production and biodegradation of dissolved carbon, nitrogen and phosphorus from Canadian forest floors
Bibliographic record
Abstract
Dissolved organic matter (DOM) is operationally defined as soluble/colloidal material passing through a 0.45mum filter paper. The importance of DOM in soils relies on its role in soil formation and weathering processes, plant and microbial assimilation and soil and water acidification. However, the scientific community studying DOM still disagrees on whether fresh or humified material is the major source of DOM within the forest floor. One of the factors that could influence the overall importance of DOM production by organic horizons is its potential for biodegradability. In addition, the interaction occurring between the nutrients (i.e. nitrogen (N) and phosphorus (P)) and carbon (C) substrate is believed to be of major importance. To acquire more knowledge on the production and biodegradation of dissolved C, N and P during decomposition of organic matter (OM), I performed laboratory incubations to evaluate rates of production and transformation, the influence of the degree of OM decomposition and stand type on these rates, and the stoichiometric relationships of the different quotients during the incubations. First, I performed a 30-day incubation of coniferous and deciduous OM from 10 Canadian forest floors representing various degrees of OM decomposition and subsequently measured the amount of: dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N), ammonium (NH4-N), dissolved organic nitrogen (DON), total dissolved phosphorus (TOP) and carbon dioxide (CO2-C). I performed water extractions with the same set of samples to evaluate the biodegradability of DOC and DON and the transformations of TDN, NO3-N and NH4-N. Fresh material produces more DOM than humified material; material in the midpoint of decomposition (F horizon) produced the largest amount of DIN. Coniferous and deciduous samples did not display different rates of DOM production, most likely because of the overshadowing effect of OM degree of decomposition. I found strong links between the organic matter and dissolved phase C and N content and C:N quotient. The biodegradation, measured as DOC disappearance and mineralization of CO2-C, showed a discrepancy, reflecting the importance of increasing microbial biomass at the beginning of the incubation in response to priming effect. The sharp decrease of TDN and DON observed in the first few days of the incubation, in addition to increasing amount of dissolved inorganic N as waste products during decomposition of DON, supports this hypothesis. A better understanding of the dynamics of dissolved C, N and P in soil is essential to further understand their role in global elemental cycles, including climate change, forest management and pollution.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".