No abstract

We examined cavity-nesting bird use of natural snags (n = 221) and 10to 12-year-old snags (n = 836) created by topping mature conifers in 3 silvicultural treatments (group-selection cuts, 2-story regeneration harvests, clearcuts with retained trees) and 2 snag arrangements (clustered, scattered) in 30 Douglas-fir (Pseudotsuga menziesii) stands in the Oregon Coast Range. Eight bird species nested in created snags. Open-canopy stands (2-story and clearcut treatments) had higher levels of avian nesting, species richness, and species diversity compared to closed-canopy, group-selection stands. We did not find a difference in nesting levels between clustered and scattered snags. In created snags, most active nests were in the top 25% of the bole, cavity entrances typically faced northeast, and the presence of dead branches did not alter use of snags for nesting. Topped conifers that remained alive (n = 102) were rarely used for nesting or foraging. Since the last survey 6 years prior to our survey, the number of cavities per created snag per silvicultural treatment increased 3.3to 6-fold, and we observed 4 additional avian species nesting; 3 were secondary cavity nesters. Total cavities per snag averaged 5.1, 4.3, and 2.5 for created snags, natural snags >12 years old, and natural snags <12 years old, respectively. Only 1 created snag fell in the decade since topping. Natural new snag recruitment resulting from residual green tree mortality was highest in 2story stands (0.76 snag/ha) and lowest in clearcuts (0.20 snag/ha). Snags created by topping large conifers provided nesting and foraging structures for cavity-nesting birds under a range of silvicultural conditions, and use was influenced more by residual green tree density than snag arrangement. In addition, created snags increased in value for birds through their first decade (88% had cavities). Because snags created by topping last long and are readily used by birds, they should be considered a management option to improve avian habitat in managed forests. JOURNAL OF WILDLIFE MANAGEMENT 69(4):1578-1591; 2005

No abstract

This study assessed growth, condition, and mortality of residual trees one decade after harvest across three silvicultural treatments in thirty 85-to 125-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in the Oregon Coast Range foothills. Group-selection cuts had 33% of the entire stand volume extracted as patches approximately 0.2-0.8 ha in size; two-story regeneration harvests had 75% of the volume extracted, and 20-30 residual trees/ha were left; clearcuts had all trees removed, except for 1.2 trees/ha. One decade after harvest, tree basal area, diameter, and height growth, and crown width and fullness did not differ between silvicultural treatments. In contrast, live crown ratio was largest in clearcuts (0.74), and the proportion of trees with epicormic branching was highest in two-story stands (35%). Overall, 45% of trees had more basal area growth in the decade after harvest than in the previous decade. Residual green trees in clearcuts and group-selection stands experienced the highest and lowest percentage mortality, respectively (30.6% vs. 0.2%). Our results reflect little differentiation in the characteristics of trees growing under three silvicultural conditions one decade after harvest. However, percent residual green tree mortality increased with increasing harvest intensity.Résumé : Cette étude visait à évaluer l'effet de trois traitements sylvicoles sur la croissance, l'état de santé et la mortalité des arbres résiduels dix ans après la récolte dans 30 peuplements de douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) âgés de 85 à 125 ans et situés dans les contreforts de la chaîne côtière en Oregon. La coupe de jardinage par groupe consistait à couper 33 % du volume total du peuplement en îlots de 0,2 à 0,8 ha; la coupe de régéné-ration à deux étages consistait à couper 75 % du volume en laissant 20-30 arbres résiduels à l'hectare; la coupe à blanc consistait à couper tous les arbres à l'exception de 1,2 arbre à l'hectare. Dix ans après la récolte, la surface terrière, le diamètre et la croissance en hauteur des arbres ainsi que la largeur et la densité de la cime ne différaient pas selon le traitement sylvicole. Par contre, le rapport de cime vivante était le plus élevé dans la coupe à blanc (0,74) et la proportion d'arbres avec des branches épicormiques était la plus élevée (35 %) dans les peuplements à deux étages. Dans l'ensemble, 45 % des arbres ont eu une croissance en surface terrière plus élevée dans la décade qui a suivi la récolte que dans celle qui a précédé. Les arbres résiduels dans la coupe à blanc et la coupe de jardinage ont connu respectivement le plus haut et le plus faible taux de mortalité (30,6 % versus 0,2 %). Nos résultats indiquent qu'il y a peu de différentiation dans les caractéristiques de croissance des arbres dans trois traitements sylvicoles dix ans après la ré-colte. Cependant, le pourcentage de mortalité des arbres résiduels augmente avec l'intensité de la récolte.[Traduit par la Rédaction] Walter and Maguire 1978

No abstract