Caractéristiques de la forêt boréale de l'Est du Québec en relation avec la faune aviaire

Les objectifs de ce projet étaient, en premier lieu, de comprendre l’effet d’une perturbation naturelle (le feu) sur la disponibilité et l’abondance des arbres morts sur pied et sur les oiseaux résidant dans la forêt boréale non-aménagée de l’Est du Québec. En deuxième lieu, j’ai voulu comprendre l’effet des changements de structure et de composition des forêts boréales sur les communautés d’oiseaux en général et ce, le long de deux chronoséquences couvrant plus de 200 ans après feu. Mes résultats montrent que le taux de mortalité des arbres forme un patron en U caractérisé par une forte abondance de chicots dans les jeunes peuplements et dans les peuplements âgés. Ces peuplements sont caractérisés par un plus grand nombre de cavités et de signes d’alimentation de la part des oiseaux résidents. Toutefois, la richesse en espèces des oiseaux n’a que très peu varié en fonction des classes d’âge des peuplements, mais plusieurs espèces sont disparues et d’autres ont été recrutées en fonction des stades de succession. Cette étude souligne l’attention qu’il faut porter à tous les stades de succession de la forêt boréale, spécialement aux vieilles forêts qui procurent un environnement hétérogène requis par un grand nombre d’espèces.The first objective of this project was to understand the effect of natural fire disturbance on the availability and abundance of dead trees (snags) and their use by cavity-nesting birds in the northeastern part of Quebec’s unmanaged boreal forest stands. Secondly, I aimed to understand the effects of the structure and composition of the boreal forest on bird species communities along two long-term chronosequences after fire (0 to > 200 years postfire). Results show that tree mortality follow a U-shape pattern, with more snags in young and old-growth forests, where I also found more nest cavities and foraging signs. Although bird species richness did not vary greatly according to the different age classes, many species were lost and others recruited following succession stages. This study highlights the need to protect the forest at all stages, especially old-growth, which provides a heterogeneous environment suitable for several bird species

Efficiency of enhanced capture methods and age-class structure of dispersing boreal woodpeckers

American Three-toed (Picoides dorsalis) and Black-backed Woodpeckers (Picoides arcticus) are irruptive species for which yearly movements and abundance are linked to higher productivity years due to forest fire or large-scale insect outbreaks in boreal forests. Studies have found that, in Black-backed Woodpeckers, younger birds are the main colonizers of recent burns, and thus related to natal dispersion. However, age structure of dispersing boreal woodpeckers in the fall have yet to be studied. The Observatoire d’oiseaux de Tadoussac is a migration monitoring station located at the southern limit of Québec’s boreal forest and where a special effort has been made to count and capture transient boreal woodpeckers in the fall between 2000 and 2006. In this study, we investigated (1) the age structure and sex ratio of dispersing boreal woodpeckers and assessed (2) if the use of enhanced capture methods (ECM) improves their rate of capture and (3) the correlation between capture rates and visual counts. The age structure of Black-backed Woodpecker (1:13.9 [1:4.5–1:64] adult:juveniles ratio) and American Three-toed Woodpecker (1:16.7 [1:4.22–0]) was strongly skewed toward juveniles, and suggests that dispersing individuals were mainly related with post-fledging movements. The use of ECM to capture boreal woodpeckers was an efficient way of capturing these species. This method showed capture rate four times greater than the passive method. Moreover, capture rates were correlated with visual counts. Therefore, our study supports the importance of post-fledging movements in boreal woodpecker population dynamics, and shows that the use of ECM is an efficient method to capture and count these species outside their breeding season

Metabolic dysfunction and altered mitochondrial dynamics in the utrophin-dystrophin deficient mouse model of duchenne muscular dystrophy.

The utrophin-dystrophin deficient (DKO) mouse model has been widely used to understand the progression of Duchenne muscular dystrophy (DMD). However, it is unclear as to what extent muscle pathology affects metabolism. Therefore, the present study was focused on understanding energy expenditure in the whole animal and in isolated extensor digitorum longus (EDL) muscle and to determine changes in metabolic enzymes. Our results show that the 8 week-old DKO mice consume higher oxygen relative to activity levels. Interestingly the EDL muscle from DKO mouse consumes higher oxygen per unit integral force, generates less force and performs better in the presence of pyruvate thus mimicking a slow twitch muscle. We also found that the expression of hexokinase 1 and pyruvate kinase M2 was upregulated several fold suggesting increased glycolytic flux. Additionally, there is a dramatic increase in dynamin-related protein 1 (Drp 1) and mitofusin 2 protein levels suggesting increased mitochondrial fission and fusion, a feature associated with increased energy demand and altered mitochondrial dynamics. Collectively our studies point out that the dystrophic disease has caused significant changes in muscle metabolism. To meet the increased energetic demand, upregulation of metabolic enzymes and regulators of mitochondrial fusion and fission is observed in the dystrophic muscle. A better understanding of the metabolic demands and the accompanied alterations in the dystrophic muscle can help us design improved intervention therapies along with existing drug treatments for the DMD patients

Transmission electron microscopic images show mitochondrial localization is altered in DKO EDL muscle.

<p>A) WT EDL B) DKO EDL at 14000X magnification. C) WT and D) DKO at 34000x magnification. The arrows point to the localization of mitochondria (M) which are at the I band on either side of the Z disc in WT, but this tight localization is reduced in the DKO EDL.</p

Increased oxygen consumption relative to integral force.

<p>A) The fatigue profile of WT and DKO EDL during the 10 minutes fatigue shows that DKO EDL generates lesser force and fatigues less. B) The % of initial force after the 10 minute fatigue is higher in DKO EDL indicating less fatigue (p = 0.0019). C) The quantified force time integral over the entire 10 minutes fatigue protocol is significantly reduced in the DKO EDL compared to WT (p = 0.0097). D) Oxygen consumption over 10 minutes fatigue is not significantly different in WT and DKO EDL muscle. E). Oxygen consumed per unit integral force produced is significantly higher in DKO EDL compared to WT (p = 0.0110). p< 0.05 is significant. * = p<0.05, ** = p<0.01.</p

Whole body energy expenditure of WT and DKO mice.

<p>A) Rate of oxygen consumption in DKO mice is not significantly different from WT at both night and B) day. Respiratory exchange ratio (F) is similar in WT and DKO mice both at C) night and D) day. Activity counts measured in WT and DKO mice during E) night and F) day. Activity counts are significantly reduced (p = 0.0060) in DKO mice at night compared to WT. Oxygen consumption per unit activity is significantly higher in the DKO mice both during G) night (p = 0.0023) and H) day (p = 0.0463) p<0.05 = significant. * = p<0.05, ** = p<.01.</p

Increased potentiation of force by pyruvate in DKO EDL.

<p>A). Effect of substrate on force production showing an increase in force production using pyruvate as a substrate at lower frequencies in DKO mice. B) B) Specific force produced by WT EDL is significantly higher (p<0.05) than DKO EDL when glucose is used as a substrate at 50 Hz. In the presence of pyruvate the specific force produced by WT EDL is not significantly different from DKO EDL at 50Hz. There is a significant increase in force production in DKO EDL when pyruvate is used as a substrate compared to glucose (p<0.05). However, the force produced by WT EDL in the presence of pyruvate is not significantly different from the force produced in presence of glucose. C) % Increase in force using pyruvate as a substrate relative to glucose is significantly higher in DKO EDL compared to WT at 30Hz (p = 0.0033) and D) 50Hz (p = 0.0011). p< 0.05 is significant. * = p<0.05, ** = p<0.01.</p

DKO mice weigh less but consume similar amount of food when compared to WT controls.

<p>A) DKO mice weigh significantly less than WT (p = 0.0298). B) Food consumption between WT and DKO mice is not significantly different.</p