This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not illustrated.
1915 Excerpt: ... summer and winter is quickly exerted in an
elevation of the soil moisture, but at the close of these seasons
it is with relative slowness that the soil falls to low percentages
of moisture, particularly at the highest altitudes. The minimum
moisture content of the year is usually to be detected just before
the first heavy rain of the humid mid-summer, but the content in
September or October may sometimes be quite as low. At low
elevations in the Santa Catalinas the annual march of soil moisture
may be expected to be analogous to that which has been described by
the writer for Tumamoc Hill, the site of the Desert Laboratory?'
Marked differences will result from a comparison of the two
localities, however, owing to the difference in the character of
the soil. The very fine clay of Tumamoc Hill is conservative in its
changes of moisture content, both with respect to increases and
decreases of moisture. while the coarse loam found at the lower
elevation in the Santa Catalinas possesses a greater permeability
and a lesser holding power. The soils of elevations of 7,000 feet
and more are richer in organic matter than those of the Desert and
Encinal regions of the mountain, and are doubtless more like the
clay of Tumamoc Hill in the smoothness of their curves of change in
moisture content. The few readings of soil moisture content that
have been made were directed toward a determination of the soil
conditions in the most arid portion of the year. It is obvious that
it is these annual minima which are of the greatest importance to
plants, particularly to such plants as are near the lowest limit of
their vertical occurrence. Much less interest attaches to the high
moisture contents which might be found in the midst of the rainy
seasons. It is true that these ...
|Country of origin:
Carnegie Institution of Washington
||246 x 189 x 3mm (L x W x T)
||Paperback - Trade
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