Notice bibliographique
Résumé
Fire is globally one of the main disturbance agents that regulate and shape ecosystems and this has been so for millennia. Globally, there has been a discrepancy between the global emergence of extreme fire weather from a warming climate which promotes fires and a recent decrease in burned area of around 25% between 1998 and 2015. However, in parts of the world, known as the extratropics, a positive relationship between more extreme fire weather and burned area has been observed. Especially the vast areas of boreal forest are less influenced by human activity, and thus burned area is driven by lightning ignitions. Globally, 2.5% of the annual burned area stems from boreal forest fires while a recent study found that 14% of the annual global carbon emission comes from boreal forest fires. The high fuel consumption and thus high emissions of carbon per unit burned area in the boreal forest has also caused the global fire carbon emissions to stabilize even with declines in global burned area. The important role of boreal fires on a local, regional, and global scale and its intricate interactions with carbon and vegetation dynamics as well as climate change, illustrates the need for a better understanding of the prerequisite drivers of boreal fire ignitions and the newly discovered overwintering fires. This thesis responds to the need by quantifying the importance of snow disappearance and the dynamic interplay between lightning, fuel, and fire weather on ignition and overwintering fires in boreal North America. Recent changes in snow disappearance timing and the number of fire ignitions across boreal North America showed a clear west-east divergence. Regardless of the spatial and temporal trends, the snow disappearance timing correlated significantly positively with the timing of the ignitions across all ecoregions in boreal North America. This relationship, however, was observed for all ignition sources i.e. human, lightning, and unknown. The annual earliest 20% ignitions resulted in fires growing around 77% larger on average compared to the late-season ignitions. Warm and dry weather as well as fuel loads also promoted snowmelt and ignition timing. Similarly, the lightning ignition efficiency over Alaska, USA, and the Northwest Territories, Canada was largely driven by top-down fire weather conditions. The short-term (within a day) drying of organic soils and the lack of precipitation accompanying the thunderstorm influenced the lightning ignition efficiency strongly. Especially the occurrence of dry lightning (less than 2.5 mm precipitation) exerted an important control over lightning ignitions in boreal forests, but it can vary at landscape scale. Recent climate changes have also led to changes in the fire season length with overwintering fires being more prevalent. By spatiotemporally extrapolating our algorithm, we estimate that around 1% and 1.2% of the total burned area stemmed from reburning of overwintering fires between 1986 and 2020 in Interior Boreal Alaska and the Taiga Plains. Denser evergreen forest in microtopographical uplands were more prone to overwintering reburns. This indicates that productive forests may provide mechanisms for overwintering reburns by combustion of tree boles and roots.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,001 | 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 | 0,001 | 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 | 0,002 |
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; les deux têtes enseignantes s’accordent sur ce qui est montré ici.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».