The decrease in the rain- and snow-fall since the close of the glacial
period in the Sierra is much less than is commonly guessed. The highest
post-glacial watermarks are well preserved in all the upper river
channels, and they are not greatly higher than the spring floodmarks of
the present; showing conclusively that no extraordinary decrease has
taken place in the volume of the upper tributaries of post-glacial
Sierra streams since they came into existence. But in the mean time,
eliminating all this complicated question of climatic change, the plain
fact remains that _the present rain- and snow-fall is abundantly
sufficient for the luxuriant growth of Sequoia forests_. Indeed, all
my observations tend to show that in a prolonged drought the Sugar Pines
and firs would perish before the Sequoia, not alone because of the
greater longevity of individual trees, but because the species can
endure more drought, and make the most of whatever moisture falls.
Again, if the restriction and irregular distribution of the species be
interpreted as a result of the desiccation of the range, then instead of
increasing as it does in individuals toward the south where the rainfall
is less, it should diminish.
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