Carbon isotope discrimination in western hemlock and its relationship to mineral nutrition and growth
Notice bibliographique
Résumé
Western hemlock (Tsuga heterophylla [Raf.] Sarg.) is a major component of temperate rainforests in coastal British Columbia. Forest fertilization can enhance the growth of forest trees, but results are inconsistent for western hemlock. We investigated the relationship between delta13C (foliage and stemwood), growth response and tree nutritional status in this species. To establish a sampling protocol for stemwood, we first assessed spot-to-spot variation around and along the bole, which exceeded 1 per thousand. We utilized the reaction wood (high lignin content) and adjacent normal wood in two curved western hemlock stems to evaluate whether this variation was related to wood composition. There was a consistent 3.43 per thousand difference between lignin and holocellulose, but the isotopic mass balance of whole wood was conserved and, therefore, did not vary with lignin content. Therefore, extraction of cellulose or holocellulose prior to analysis can introduce (not remove) bias. In a detailed study of a third stem, circumferential and longitudinal variation in delta13C was associated with spiral grain indicating limited physiological mixing of isotopic signatures originating from the crown. Wood was subsequently pooled from four cardinal positions around each stem. Eight even-aged western hemlock stands were selected and fertilized with different combinations of nitrogen (N), phosphorous (P) and a blend of S, K, Mg, Zn and Cu. Fertilization was effective in increasing foliar N, P, K and S depending on treatment. At the end of the first growing season after fertilization, the effect of treatments on foliar delta13C was nearly significant (P = 0.054), but did not persist into a second year. Effects on tree-ring delta13C were more obvious and persisted for about 3 years, averaging approximately 0.2-0.4 per thousand over this period, depending on treatment. Combinations of N, P and blend had the greatest effect, consistent with relative increases in basal area increment. Effects of fertilizer additions on delta13C, though clear, were superimposed on larger site and annual weather-related patterns in delta13C. Large tree-to-tree variation in delta13C was positively correlated with basal area increment, both before and after treatment imposition, suggesting that high water-use efficiencies are associated with greater growth.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».