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Re: 45 MYA Redwoods Found Near North Pole



>>  We dont have plants that can survive under those conditions today, let
>>  alone forests, Jahren says. For a tree to endure four months of daylight
>>  is like you or I going without sleep for four months.

>Keeping in mind that the "dark reaction" of photosynthesis (the fixation of
>carbon) is a total misnomer, as it can only take place when light is
>present, I don't understand why constant daylight would harm plants. Does
>someone know?

Constant daylight in summer does _not_  hurt plants. On the contrary they
thrive on it. Since I live at latitude 60 in Sweden and has spent a fair
amount of time north of  the Arctic Circle I feel confident on this point.
The limiting factors is not the light regime, but the hardness of the
winters and the length of the growing season. In protected spots where the
local climate and soil is good vegetation can be quite amazingly luxuriant
even inside the arctic circle.
Actually here in Scandinavia where the climate is moderated by the Gulf
Stream many southern plants will grow at surprisingly high latitudes. For
example I've seen _Metasequoia_  grow at 55 1/2 degrees latitude in Denmark
(= central Labrador or the Alaska panhandle), and they are probably not the
northernmost ones.

It should also be noted that the light regime at high latitudes does _not_
consist of six months daylight and six moths night. On the contrary it is
characterized by very long twilight periods all year around. If the climate
was warm enough I should think that low latitude species adapted to low
light levels (e. g. forest understorey forms) would do very well at high
latitudes.

Also, with a mild polar climate one of the worst effects of the long
winters on plants would disappear: the drought. This is because plants
cannot absorb moisture from frozen soil and many (most?) plants that die in
northern winters are actually killed by this rather than the cold.

Tommy Tyrberg