Quote:
Originally Posted by O-tacular
It's not the cold that is inhospitable to trees here. It's the fact that Calgary and southern Alberta are basically in a near desert climatic zone. Visit here sometime and you'll understand. First thing you'll notice is dry eyes, nosebleeds, cracked / bleeding lips and dry chapped skin on your hands. Winter is the worst. Summer isn't nearly as dry but is still generally quite dry. July is kind of a weird monsoon season where you see tons of thundershowers and hailstorms.
The erratic weather patterns and elevation probably don't help either. I think Calgarian already alluded to the constant freeze thaw cycles that occur as well as early frosts. Interesting fact about growing seasons: My inlaws live in Calgary's SW at a very high elevation since it is basically the beginning of the foothills. Their growing season is something like 2 weeks shorter than in my end of the city which is at prairie level. They also get snow much sooner and it also seems to linger quite a bit longer. The fact they live in an aspen forest probably makes this worse.
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Yeah, I did mention the relative lack of rain in my list of factors. But you're probably right in insisting on its importance.
I'd think at first sight that long-ish periods of dipping deep below zero after the buds have emerged would be a killer too. The Eastern trees have not evolved to face this, though they can survive -40C.
Speaking of Eastern hardwoods, I seemed to recall that the American Elm's native range included the Canadian Prairies, so I just looked it up. It stops at mid-Saskatchewan. Is Edmonton really drier than central SK? I thought the Parkland Belt (or is it Ukrainian Belt?) had relatively similar characteristics from East to West. Turns out it's not the case, at least for elms.
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