Effects of Forest Harvesting on Nest Predation in Cavity-nesting Waterfowl
Notice bibliographique
Résumé
Waterfowl populations inNorth America are threatened by habitat loss (Owen and Black 1990), but effects of habitat destruction and fragmentation on waterfowl nesting in forested landscapes are poorly known.Increased nest predation is often attributed to habitat fragmentation and may be particularly evident in smaller habitat patches and at habitat edges (Paton 1994, Andrn 1995).However, relatively few studies conducted in forest-dominated landscapes show edge effects at either natural or anthropogenic edges (Paton 1994, Andrn 1995, P6ysa et al. 1997).Lack of edge effects in forest-dominated landscapes may be due to relatively low predator species richness and abundance, and lack of predator attraction to edges (Andrn 1995).However, predator abundance and nest predation may increase with increased deforestation of the landscape (Andrn 1995, Hartley and Hunter 1998).Effects of habitat destruction and fragmentation on nest predation of cavity-nesting waterfowl are unknown.We know of only one study of nest predation in cavity-nesting waterfowl in forest-dominated landscapes (P6ysa et al. 1997).This study found no edge effects at natural (lake) edges in a forested landscape, but did not investigate effects of forest harvesting.Thus, we experimentally investigated effects of forest harvesting on cavity-nesting waterfowl in the boreal mixedwood forest of western Canada, an important breeding and summering area for waterfowl.Although deforestation and fragmentation have proceeded relatively slowly in that region, large areas of forest have recently become available for harvesting.We used artificial waterfowl cavity nests E-mail: jpierre@gpu'srv'ualberta'ca to test the following hypotheses: (1) nest-predation levels in cutblocks (clearcuts with ->8% of trees remaining) differ from predation levels in uncut forest, (2) nest-predation levels in riparian forest buffer strips differ from predation levels in uncut forest, (3) nest-predation levels in uncut forest vary with distance from the riparian forest edge, and (4) nest predation is higher around lakes in harvested versus unharvested landscapes.Methods.--Weconducted research from May through July in 1997 and 1998, in the boreal mixedwood forest surrounding 10 lakes in north-central Alberta, Canada.Six of the 10 study lakes were part of the TROLS (Terrestrial and Riparian Organisms, Lakes and Streams) project, a large-scale multidisciplinary study using experimental forest harvesting protocols at 12 lakes to determine effects of different buffer strip widths on aquatic and terrestrial boreal systems.Study lakes were in three clusters and ranged in size from 8.6 to 103.6 ha.Forests surrounding study lakes were dominated by trembling aspen (Populus tremuloides), balsam poplar (P.balsamifera), white spruce (Picea glauca), black spruce (P.mariana), and jack pine (Pinus banksiana).Extensive commercial forest harvesting began in this region in 1993.Forest harvesting is carried out in two to three passes 10 years apart, creating a mosaic landscape of harvested patches of various ages and unharvested stands.Average cutblock size is approximately 30 ha and cutblocks contain ->8% residual trees.When forest surrounding lakes is harvested, a forest buffer strip 100 m wide separates riparian vegetation and the adjacent lakeshore from harvesting activity.The purpose of buffer strips is to protect lake water quality.(Although riparian vegetation separated the forest from the lake edge around
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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.
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