Forested buffer strips are left along water bodies after forest harvesting to protect water quality and fish stocks, but little is known about their utility as reserves for forest species in managed landscapes. We report on changes in terrestrial vertebrate communities from pre-to post-harvest in experimentally created buffer strips (20, 100, 200, and 800 m wide) in a boreal mixedwood forest in Alberta, Canada. We trapped anuran amphibians and small mammals and spot-mapped bird territories around 12 lakes (4 treatment levels, 3 replicates) before and after harvesting. Changes in small mammal or amphibian abundance were not detected for any treatment relative to controls; however, these species are habitat generalists that used and even bred in clearcuts. Total bird abundance did not change after harvesting, with the exception of crowding in 20-m buffers 1 year post-harvest. Species composition did not change for amphibians and small mammals after harvest, but forest-dependent bird species declined as buffer width narrowed from 200 to 100 m and narrower. We concluded that 20-100 m buffers would not serve as reserves for forest songbirds in managed landscapes, but that 200 m wide strips conserved the pre-harvest passerine bird community, at least up to 3 years post-harvest.Résumé : Lors de coupes forestières, des lisières boisées sont laissées le long des plans d'eau pour protéger la qualité de l'eau et les stocks de poissons. On sait peu de choses de leur utilité comme réserves pour les espèces forestières dans les paysages aménagés. Nous avons documenté les changements dans les communautés de vertébrés terrestres avant et après coupe, dans des lisières boisées expérimentales (20, 100, 200 et 800 m de largeur), dans une forêt boréale mixte de l'Alberta, au Canada. Nous avons piégé les anoures (amphibiens) et les petits mammifères et inventorié les oiseaux par cartographie des territoires autour de 12 lacs (4 niveaux de traitements, 3 répétitions), avant et après coupe. Aucun changement d'abondance des petits mammifères et des amphibiens n'a été détecté dans les traitements par rapport aux témoins, mais ces espèces sont des généralistes qui utilisent et même nichent dans les coupes à blanc. L'abondance totale d'oiseaux n'a pas changé après coupe, à l'exception d'une concentration dans les lisières de 20 m l'année après coupe. La composition spécifique en amphibiens et petits mammifères n'a pas changé après coupe, mais les espèces d'oiseaux dépendants de la forêt ont décliné en relation avec le rétrécissement des lisières de 200 à 100 m et moins. Nous concluons que les lisières de 20-100 m ne servent pas de réserves pour les oiseaux forestiers dans les paysages aménagés tandis que les lisières de 200 m de largeur conservent les communautés d'oiseaux d'avant coupe au moins durant les 3 années suivant la coupe. [Traduit par la Rédaction]Hannon et al. 1800
Development of appropriate conservation plans relies on life-history information and how life-history traits vary across populations of a species. Such data are lacking for many amphibians, including the Canadian Toad (Bufo hemiophrys Cope, 1886). Here we use skeletochronology to estimate size at age, growth rates, age at maturity, and longevity of toads from nine populations along a latitudinal gradient in Alberta, Canada. Size of individual toads within each year class was highly variable, but age and size (measured as snout-to-urostyle length) were significantly related for almost all populations. The largest individuals were found in the southern-most population, while the smallest toads were found in three populations from the middle of the latitudinal range studied. Growth rates were highest in the southern-most population and lowest at the three populations with relatively small individuals. Maximum age was from 7 to 12 years for the populations sampled. The oldest individuals were found in populations in the middle of the latitudinal range sampled; toads in these populations were smaller than those in all other populations. Age at maturity was 1 year old for males and 2 years old for females in most populations. This study shows that some life-history traits exhibit significant variation between Canadian Toad populations, suggesting that effective conservation of this species will need to include population or area-specific management.
SUMMARY : Penicillin-sensitive and penicillin-resistant colonies of Staphylococcus aureus, belonging t o the same phage pattern, were found in six out of 200 apparently resistant cultures isolated from infective processes. The in vitro instability of penicillinase-producing strains of Staph. aureus was confirmed. It was found that growth with Streptococcus haemolyticus or in the presence of other antibiotics did not greatly influence the natural development of sensitive variants. This process, however, tended to be accelerated by growth at 44", although some strains did not yield any sensitive variants in spite of prolonged incubation. Some inherited factor is considered to be primarily responsible for the production of penicillinase.
We exploited fish winterkills in small, boreal Alberta lakes to determine if anuran amphibians respond to large but natural changes in fish densities. Eight large declines in fish abundance occurred in seven lakes over a 5 year period, while major increases in fish abundance, reflecting recovery after winterkill, were recorded 5 times. Summer pitfall trapping of young-of-the-year (YOY) Wood Frogs (Rana sylvatica LeConte, 1825) and Boreal (Bufo boreas boreas Baird and Girard, 1852) and Canadian (Bufo hemiophrys Cope, 1886) toads indicated that frog abundance responded consistently to such large changes in fish abundance, but especially if fish communities were dominated by small-bodied species (sticklebacks and minnows). As well, changes in YOY Wood Frog and fish abundance were negatively correlated; YOY Wood Frogs were as much as 7.7 times more abundant after winterkills than in non-winterkill years. These increases in metamorphs did not result from an increased immigration of breeding adults to winterkill lakes, suggesting instead that larval survival was greater. Higher abundance of YOY Wood Frogs and toads was associated with smaller body size at metamorphosis. Despite this apparent reduction in individual growth, abundance of juvenile frogs remained significantly elevated 1 year after winterkill. In contrast to Wood Frogs, YOY toads tended to respond positively to recoveries of small-fish populations. Because anuran amphibians can respond to fish winterkill, and because winterkill is a frequent natural disturbance, small fish-bearing lakes can serve as important breeding habitat for amphibians in Alberta's boreal forest.
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