Sequential Extractions of Elements in Tree Rings of Balsam Fir and White Spruce
Bibliographic record
Abstract
Many attempts have been made to reconstruct past soil chemistry from tree rings' total element concentrations. However, a few recent studies have shown that some elements are highly mobile within some tree species' sapwood, which may complicate the interpretation of temporal trends. To investigate element mobility in xylem of balsam fir (BF) and white spruce (WS), a dendrogeochemical method was utilized, which consists in sequentially extracting tree ring samples with water and diluted hydrochloric acid (HCl; 0.05 M) followed by a complete digestion in nitric acid (residual). The results show that, within the sapwood of BF and WS, potassium (K) and phosphorus (P) are found mostly in the water extract whereas divalent cations [calcium (Ca), magnesium (Mg), strontium (Sr), manganese (Mn), zinc (Zn), and barium (Ba)] are mainly present as soluble or exchangeable forms. Total xylem concentration generally decreased in the following order for both tree species: Ca > Mg > Mn > Zn, Ba > Sr. At the opposite, the vast majority of aluminum (Al) (>99%) and iron (Fe) (>95%) is found in the residual fraction, suggesting that these elements are not affected by radial reequilibration during circulation of the sap. Because Al soil availability is known to increase with decreasing pH, this element can potentially be used for past reconstruction of soil pH.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| 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 teacher head, 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".