Sunday, October 21, 2007

Danse Macabre

The way these birches lurched back and forth in a gusting wind against a gloomy sky suggested dancing skeletons. Chances are they will be skeletons soon anyway; birches don't live long here for several reasons. One is that they are colonizers and naturally short-lived (grow fast and die). Another is the alternately water-logged or desiccated, nutrient poor, peaty soil, which most trees find stressing. A third is beetles, both domestic and foreign, which burrow into the cambium, lay eggs, and introduce fungi, which will become a food source for their larvae. Xylem become clogged, branches die and fall off, and eventually the tree dies. One such beetle is the Ambrosia Beetle, named for its associated fungus. It parasitizes both softwoods and hardwoods, including paper birch. Smaller than a grain of rice, but a menace to forests --a concept now familiar to residents of this province, where a similarly-sized beetle (the Mountain Pine Beetle) is decimating the interior pine forests, and rapidly spreading elsewhere.

Ambrosia Beetle, Trypodendron lineatum, or a relative (not positively identified) from a paper birch down the road.

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