Role of safe sites in black spruce recruitment and growth release in post-fire Kalmia heath
Notice bibliographique
Résumé
The goal of this thesis was to explain black spruce regeneration in postfire sheep laurel (Kalmia angustifolia L., hereafter referred to as Kalmia) dominated chronosequence in light of safe site density. The concept of safe site was expanded by including germination as well as seedling establishment and growth phases. Proliferation of Kalmia, which dominates heathlands of eastern Newfoundland, has been reported to severely restrict conifer recruitment and growth. As a result, forest regeneration in Kalmia heath can be delayed by as much as 60 years. Despite numerous studies, the process by which colonization and establishment of black spruce occurs in Kalmia heath is poorly understood. \nThis problem is addressed in two chapters. In chapter one, it was hypothesized that post-fire black spruce stem density, which represents a relative measure of safe site abundance per plot, is a function of variation in microsite conditions, rather than time since fire. The second hypothesis was that the partially safe sites defined by seedling establishment, but poor seedling growth, overtime, become safe sites allowing a growth release. In chapter two, it was hypothesized that microsites created by scarification and microsite mulching (MSM) enhance black spruce growth by removing the inhibitory effects of Kalmia and its organic matter by increased decomposition and soil moisture. \nThe main findings of the research are (1) black spruce safe site density in \npost-fire sites is low and diminishes over time; (2) relative safe site density is negatively associated with organic matter thickness; (3) most of the recruited black spruce experience a period of stunted growth; (4) with time, stunted black spruce may overcome the growth check; (5) the likelihood of the growth release has an inverse relationship with OM thickness and positive relationship with OM decomposition; (6) young black spruce seedlings planted in artificially created safe sites show significantly higher growth rates compared to those in undisturbed heath. Based on these results, it was concluded that i) safe sites play a critical role in colonization and growth of black spruce, ii) high OM depth \n(> 5 cm) makes a microsite unsafe for black spruce regeneration, and iii) safe sites created by scarification and microsite mulching (MSM) can enhance black spruce regeneration in Kalmia health. By examining the problems of black spruce forest regeneration in Kalmia \ndominated sites, this study advances the current understanding of the safe site concept and its application in forest restoration. From the conceptual point of view, it revealed the need for extending the safe site concept beyond the germination stage to include seedling and adult life stages. This research demonstrates that by removing the growth limiting conditions, it is possible to create safe sites by scarification and MSM which enhance conifer growth in habitats that are otherwise unsuitable for conifer regeneration. For national parks and other conservation areas MSM is preferred to scarification for its minimum soil disturbance.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 | 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) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».