Post-Fire Habitat Heterogeneity Leads to Black Spruce–Kalmia L. Shrub Savannah Alternate State
Bibliographic record
Abstract
Many nutrient-poor coarse-textured Kalmia L.–black spruce forest sites in eastern Canada turn to ericaceous heath dominated by Kalmia angustifolia L. after clearcutting and fire. While the mechanisms of post-fire forest and heath formation have been well documented, the origin of shrub savanna vegetation has received limited attention. This study demonstrates the significance of post-fire island regeneration of black spruce in Kalmia heath to the origin of shrub savannah alternate state. The study was conducted in Three Brooks, 10 km west of Grand Falls-Windsor, Newfoundland (48°51′ N; 55°37′ E). Black spruce forest in the site was clearcut, then a wildfire burned the area, and the site was subsequently planted with black spruce. Plant species cover, black spruce growth (stem density, stem height, basal diameter, and yearly volume increment), and foliar nutrients of planted spruce and soil properties (pH, humus and Ae horizon depth, and nutrients) in tree islands were compared with adjacent Kalmia heath. Black spruce islands had significantly lower cover of Kalmia and higher stem density of black spruce compared to Kalmia heath (7100 stems/ha in islands vs. 1920 stems/ha in heath). Height, basal diameter, and yearly volume increment of black spruce were more than three times higher in spruce islands than in Kalmia heath. Foliar nutrients of black spruce growing in Kalmia heath had significantly lower N and Mg (33 and 38%, respectively) but had significantly higher Mn and Zn (46 and 33%, respectively) than in black spruce islands. Black spruce growth inhibition in Kalmia heath is attributed to soil nutrient imbalance due to Kalmia evidenced by reduced concentrations of N and Mg and increased concentrations of Al, Fe, and other inorganic ions in the foliage. These results suggest that post-fire black spruce islands in severely burned patches provide “safe sites” for spruce regeneration, whereas Kalmia heath developing in non-severe burn area inhibits spruce regeneration and creates shrub savannah community as an alternate vegetation state.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.007 |
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; both teacher heads agree on what is shown here.
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".