is temp the limiting factor on range

[Michael Gochfeld]

Interesting.  My botany professor who did his PhD at UNiv Chicago in the
1920's put thermocouples in tree buds and showed that bud opening was related
to (dependent on???) the cumulative degree days above some threshold (which I
have forgotten). I think he was working with American Elm (Ulmus americana).
The implication (if I remember correctly) was that  two days at 10 degrees
above threshold had the same effect as 20 days of one degree above threshold.

There's probably a literature on this for insect physiology as well.

Mike Gochfeld

Kenelm Philip wrote:

>         This probably has little to do with the situation in the SE U.S.,
> but in the arctic the limiting factor for the distribution of butterflies
> appears to be the number of degree-months above 0 C in the summer, and not
> anything to do with winter temperatures. The major exception to that rule
> is involved with the amount of summer cloudiness--but that is still unre-
> lated to winter temperatures.
>
>                                                         Ken Philip
> fnkwp at uaf.edu
>
>
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