Biogeochemical cycling of macroelements in black spruce (Picea mariana (Mill.) B.S.P.) ecosystems, quantifying precipitation and litterfall fluxes
Bibliographic record
Abstract
This study was designed and implemented (June, 1993-May, 1996) to provide a detailed examination of nutrient cycling in key ecosites (3) within a black spruce ('Picea mariana' (Mill.) B.S.P.) site array (fresh to wet on shallow-to-bedrock sites) situated in northwestern Ontario. These three sites were instrumented, using standard collection devices, to determine the nutrient fluxes associated with both precipitation (incident precipitation, throughfall, and stemflow) and litterfall for five macroelements: nitrogen (N), total phosphorus (TP), potassium (K), calcium (Ca), and magnesium (Mg). The mass and macroelement deposition rates via litterfall ranged considerably across the three study sites (site 1 > site 2 > site 3), with ranges for mass, N, P, K, Ca, and Mg of 2511-886, 11.4-4.4, 1.0-0.3, 2.4-6.9, 17.8-6.5, and 1.6-0.6 kg · ha-1 · yr-1, respectively. The amount of solutes cycled within these stands on an annual basis via precipitation for TKN, TP, K, Ca, and Mg were 0.0, 0.0, 3.8, 2.4, and 0.7 kg · ha-1 · yr-1, respectively. Based on these data, it is evident that litterfall represents the main vector for N, (TP), and Ca returns to the forest floor. On the other hand, nearly 75% of the K cycled within these stands is in precipitation. In throughfall, the three major cations studied (K, Ca, Mg) showed an increasing trend in concentration as the season progressed to a maximum in October. In the case of TKN and TP, relatively stable levels in throughfall concentration were reported throughout the summer, peaking in September, but dropping substantially in October. With respect to litterfall, the data clearly illustrated a pulse in litterfall mass in late autumn for all three study sites, although the magnitude of this pulse differed between sites. Macroelement depositions largely followed the seasonal pattern described for litterfall mass. In terms of litter components, needle litter represented a much higher percentage (nearly 80%) in this autumn pulse. Data was presented that supported retranslocation of foliar N (40-60 %) and P (50-60 %) during senescence in black spruce ecosystems; whereas, foliar K appeared to be leached out of foliage prior to needle drop and deposited on the forest floor as a solute. As forestry moves into a new era of intensive management, studies such as this one that describe key ecosystem processes within natural systems will prove to be invaluable as benchmarks to gauge the sustainability of these various management alternatives.
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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 | 0.000 |
| 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) | 0.000 | 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 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".