Land‐use effects on resource net flux rates and oxygen demand in stream sediments
Bibliographic record
Abstract
Summary Human land use in stream catchments modifies biogeochemical cycles. Here, 19 streams across a land use and cover gradient were investigated to determine how the landscape and associated conditions influenced sediment oxygen demand (SOD) and resource (carbon, nitrogen and phosphorus) net flux rates across the sediment–water interface of each stream. Resource net flux rates and SOD were determined from intact sediment cores collected in each stream and incubated in the dark. Stream water was then passed over the top of sealed cores, and net flux rates were determined by measuring the difference in nitrate ( ), soluble reactive phosphorus (SRP), quality and quantity of dissolved organic carbon (DOC) and dissolved oxygen between inflowing and outflowing water. Streams with more agricultural land in their catchments had higher ambient , SRP and protein‐like dissolved organic matter (DOM) and a larger fraction of DOM in a reduced oxidative state (as inferred using an optical DOM redox index). Sediment oxygen demand was best predicted by sediment organic content and was negatively related to wetland area and positively with row crop (arable) agriculture. These patterns indicate that streams affected by agriculture have relatively more nutrients and labile DOM than streams with greater wetland cover. Most (75%) of the variation in net flux into the stream sediments could be explained by ambient and protein‐like DOM. All but one stream had a net release of dissolved organic carbon (DOC) into the water column; however, streams with higher uptake rates lost carbon to the water column more slowly. Among streams, SRP net flux was low, varied between uptake and release and did not relate to landscape and ambient conditions. Phosphorus cycling was not affected by processes captured in this study. Net flux rates suggest that benthic net uptake increased with increased concentration and that more DOC was retained when the labile carbon pool increased with agricultural land use in the catchment. These links suggest that strategies put forward to increase the efficiency of removal should consider the composition of the carbon pool in addition to hydrological alterations.
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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 | 0.001 |
| 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) | 0.001 | 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".