Variation in attack by Sitka spruce weevil, Pissodes strohi (Peck), within a resistant provenance of Sitka spruce

Variation in tree height and numbers of attacks by the Sitka spruce weevil (= white pine weevil), Pissodes strohi (Peck), were studied among families of a resistant provenance of Picea sitchensis (Bong.) Carr. at two Vancouver Island sites. At Sayward, after 14 years, the number of trees attacked varied by family from 0 to 80%. A significant association was found between the percentage of trees attacked in a family and the mean height of the family. Tall families were generally attacked more. At Fair Harbour (a clonal test), only 12% of the trees from the resistant provenance have been attacked after seven years, with all but one of the attacks concentrated on one of the two families tested. A multigenic or multicomponent basis for resistance is proposed and discussed

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Probability of Damage to Sitka Spruce by the Sitka Spruce Weevil, Pissodes strobl

A nine-year record of attacks to Sitka spruce, Picea sitchensis (Bong.) Carr., by the Sitka spruce weevil (=white pine weevil), Pissodes strobi (Peck), was analyzed to determine the probability of attack on a tree based on the length of its terrninal leader. Equations describing the relationship were developed. Tall trees with long leaders had higher rates of attack than short trees with short leaders

A sequential sampling system for the white pine weevil, Pissodes strobi (Coleoptera:Curculionidae)

A sequential sampling system is described for determining degree of infestation by the white pine weevil, Pissodes strobi, in stands of spruce, Picea spp. The method requires that a maximum of 60 trees be randomly selected in sequence and that the cumulative number of infested trees be plotted against the total number of trees sampled. Sampling is stopped as soon as decision lines calculated for <10% infestation or ³20% infestation are crossed.Key words: spruce; Picea spp.; monitoring; pest managemen

Tree rings reveal a major episode of forest mortality in the late 18th century on the Tibetan Plateau

There is a growing research interest on studying forest mortality in relation to ongoing climate warming, but little is known about such events in past history. The study of past forest mortality provides valuable information for determining baselines that establish the normal parameters of functioning in forest ecosystems. Here we report a major episode of previously undocumented forest mortality in the late 18th century on the northern Tibetan Plateau, China. The event was not spatially uniform, in which a more severe mortality happened in dryer sites. We used dendrochronology to compare radial growth trajectories of individual trees from 11 sites in the region, and found that many trees showed positive growth trend, or growth release, during 1796-1800 CE. Growth releases are a proxy indicator of stand thinning caused by tree mortality. The growth release was preceded by an almost two-decade long growth reduction. Long-term drought related to weakened North Atlantic Oscillation and frequent El Nino events are the likely factors causing the tree mortality in a large area of the plateau. Our findings suggest that, besides the effect of drought in the late 18th century, large-scale forest mortality may be an additional factor that further deteriorated the environment and increased the intensity of dust storms

Influence of Fire and Mountain Pine Beetle on the Dynamics of Lodgepole Pine Stands in British Columbia, Canada

An outbreak of the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB), currently affecting over 10.1 million hectares of lodgepole pine forests (Pinus contorta Dougl.) in British Columbia, Canada, is the largest in recorded history. We examined the dynamics of even-aged lodgepole pine forests in southern British Columbia, which were undergoing this MPB outbreak. Using dendroecology and forest measurements we reconstructed the stand processes of stand initiation, stand disturbances, tree mortality, and regeneration, and explained the current stand structure and the potential MPB impacts in selected stands. Our results indicate that stand-replacing fires initiated even-aged seral lodgepole pine stands in this region. In the absence of fire in the 20th century, multiple MPB disturbances, which each resulted in partial canopy removal, modified the simple one-layer structure of the fire-origin stands by the initiation of post-MPB disturbance regeneration layers, transforming the stands into complex, multi- aged stands. Despite high overstory mortality due to the current MPB outbreak, regeneration layers, which are likely to survive the current outbreak, will provide important ecological legacies and will contribute to mid-term timber supply