Effects of stand age, disturbance type and harvesting intensity on soil microbial biomass in Picea mariana (Mill.) B.S.P. ecosystems in northwestern Ontario, Canada
Bibliographic record
Abstract
Two linked studies, utilizing black spruce stands located approximately 100 km north of Thunder Bay, ON, investigated changes in microbial biomass, activities and community structure. The first study utilized repeated sampling of three mature stands representing three ecosites (upland, well-drained; transitional, wet organic/mineral; and peatland) subjected to a range of harvest treatments (tree length, full tree, chip and bladed) applied in the winter. There was a substantial level of within-treatment and within-site variation. Orthogonal contrasts did not distinguish between mean MBC in upper and lower layers of harvest and uncut plots. MBC in the harvest plots varied with site and was related to retention and form of organic matter (harvesting slash and forest floor), changes in soil temperature and nutrient inputs. Measurements in late fall for three years following the harvest confirmed that the amount of MBC varied even under relatively stable vegetation complexes. The usefulness of MB as an ecosystem indicator is therefore questionable. The second study utilized mineral soil and organic matter from a chronosequence of upland stands (representing 5, 50 and 110 years since wildfire disturbance and 5 years since harvest disturbance) in a 16 week laboratory incubation; soil chemical and microbial activity and biomass parameters were measured regularly. C-based measures (MBC, CO2 evolution, total soluble C) did not differ with stand while nitrogen based measures did. Increases in the levels of NH4, NO3 and Total Soluble Nitrogen suggested that some microbial processes in recently burned soils differ from those in recently harvested and older, fire disturbance stands. These differences may be significant to crop tree survival and growth if available nitrogen is a limiting factor. Community level physiological profiling, using Biolog ECOplates, suggested the presence of unique microbial communities particularly in the young fire origin stand. Differences could not be related to C-sources utilized.
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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 | 0.001 | 0.001 |
| 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".