Reproduction and abundance of the wood frog (Lithobates sylvaticus) in post-harvest variable retention forests
Notice bibliographique
Résumé
Many aquatic-breeding amphibians require freshwater habitat for reproduction and terrestrial habitat for refuge, foraging, and overwintering. Variable retention harvesting is a technique where live trees and other forest features are retained during timber harvesting in patterns that emulate natural disturbance. Wood frogs (Lithobates sylvaticus) are often associated with closed-canopy deciduous forests and utilize ephemeral (temporary) wetlands for reproduction. The objectives of this thesis were to (1) investigate the factors influencing upland abundance of wood frogs in post-harvest variable retention forest stands and (2) investigate the effects of wetland size and forest canopy on hydroperiod and tadpole performance in ephemeral wetlands of Alberta’s boreal mixedwood. To address these objectives, I used pitfall traps to live capture wood frogs across 4 levels of retention harvest (clearcut [0%], 20%, 50%, and unharvested control [100%]), and 2 forest types (deciduous and conifer), in 17-year post harvest forests at the EMEND experiment in northwest Alberta. I mapped breeding sites to account for breeding site proximity and used a LiDAR-based terrain moisture index (Depth-to-Water) to account for soil moisture. I also monitored 15 small ephemeral breeding wetlands from May to August 2015, at which I documented drying dates to assess relationships between wetland size (surface area, maximum depth), forest canopy cover, and hydroperiod. In 12 of the 15 wetlands, I measured tadpole performance by sampling tadpoles over repeated sampling sessions until tadpoles completed metamorphosis or until wetlands dried. I also measured physiochemical parameters (pH, conductivity, and temperature) and primary productivity (periphyton growth) to compare conditions between open- and closed-canopy wetlands. Abundance of adult wood frogs varied by season, with most captures occurring during early spring and summer months (May and June). Harvest retention level alone had no effect on abundance, but in late season (July and August), there was a significant interaction between retention and forest type where abundance decreased with retention level in deciduous sites, and increased with retention level in conifer sites. The interaction effect, however, was weak, and differences in capture rates between retention levels were small. During late season capture rates were higher in conifer forests relative to deciduous forests, with soil moisture (lower Depth-to-Water) significantly and positively related to capture rates. These results suggest early regeneration of aspen and availability of moist microhabitats create suitable upland habitat for wood frogs in early seral stage mixedwood forests. Among breeding wetlands, hydroperiod was related to wetland size, but not forest canopy cover. Depth was most related to hydroperiod and may therefore serve as a useful criterion for prioritizing protection of ephemeral breeding wetlands during forest harvesting. Growth and development of wood frog tadpoles were faster in wetlands with less surrounding canopy cover. Water temperature was higher in open-canopy wetlands relative to closed-canopy wetlands which may help explain observed differences in performance. There was, however, were no significant difference in primary productivity between open- and closed-canopy wetlands. I conclude that timber retention level has a weak effect on relative abundance of adult wood frogs in 17-year post harvest stands. Natural regeneration of deciduous species post-harvest may help provide suitable upland habitat for wood frogs in both deciduous and conifer forests. Protection of ephemeral wetlands with adequate depth and hydroperiod will help maintain local populations of wood frogs and other amphibians in managed forests in the boreal mixedwood.
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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 | 0,001 |
| 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 ».