Forest dynamics following spruce budworm outbreaks in the northern and southern mixedwoods of central Quebec

The effects of 20th century spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on forest dynamics was examined in the southern and northern parts of the mixedwood forest zone in central Quebec, Canada. In each region, three study areas were placed in unmanaged stands that had not burned for more than 200 years. Disturbance impacts and forest succession were evaluated using aerial photographs and dendrochronology. Spruce budworm outbreaks occurred around 1910, 1950, and 1980 in both regions. The 1910 outbreak seemed to have limited impact in both regions, and the 1950 outbreak caused heavy mortality in conifer stands (mostly of balsam fir, Abies balsamea (L.) Mill.) in the southern region. The 1980 outbreak caused major mortality in the northern region, but had little impact in the southern region. Successive spruce budworm outbreaks led to a massive invasion by hardwood species in the last century in the southern region but not in the northern region. The reason for such contrasting dynamics between regions is unknown, but we hypothesize that differences in disturbance intensities, influenced by climate, played a major role. Results from this study emphasize that generalizations about the effect of spruce budworm outbreaks on forest dynamics cannot be derived from observations made during a single outbreak or at a single location

Effects of Temperature on Embryonic Development of Banana Weevil Cosmopolites Sordidus germar

Developemental threshold and thermal requirements for eggs of banana weevil, Cosmopolites sordidus Germar, were determined under laboratory conditions at constant temperatures of 15,18,25,27,30,32 and 34 \ub0C and a photoperiod of 12:12 L/D. The duration of the egg stage decreased from 34.9 days at 15\ub0 C to 4.9 days at 30\ub0 C, then increased again to 5.3 days at 32\ub0 C. Eggs did not hatch above the latter temperature although signs of embryonic development, such as formation of the head capsule, could be observed. Simple linear regression revealed a developmental threshold of 12\ub0 C and a thermal requirement of 89 days-degrees average. Highest rates of eclosion occurred between 25\ub0 C and 30\ub0 C

Effects of Temperature on Embryonic Development of Banana Weevil Cosmopolites Sordidus germar

Developemental threshold and thermal requirements for eggs of banana weevil, Cosmopolites sordidus Germar, were determined under laboratory conditions at constant temperatures of 15,18,25,27,30,32 and 34 °C and a photoperiod of 12:12 L/D. The duration of the egg stage decreased from 34.9 days at 15° C to 4.9 days at 30° C, then increased again to 5.3 days at 32° C. Eggs did not hatch above the latter temperature although signs of embryonic development, such as formation of the head capsule, could be observed. Simple linear regression revealed a developmental threshold of 12° C and a thermal requirement of 89 days-degrees average. Highest rates of eclosion occurred between 25° C and 30° C