. Bulletin. Forests and forestry -- United States. 2G A PRIMER OF FORESTRY. only 60°, while anotlier place, with an average of 7(P, may have occasional frosts. Trees which conld not live at all in the second of these places, on account of the frost, might flourish in the lower average warmth of the first. In this way the bearing of trees toward heat and cold has a great deal to do with their distribution over the surface of the whole earth. Their distribution within shorter distances also often depends largely upon it. In the United States, for example, the Live Oak does not grow in Maine, nor


. Bulletin. Forests and forestry -- United States. 2G A PRIMER OF FORESTRY. only 60°, while anotlier place, with an average of 7(P, may have occasional frosts. Trees which conld not live at all in the second of these places, on account of the frost, might flourish in the lower average warmth of the first. In this way the bearing of trees toward heat and cold has a great deal to do with their distribution over the surface of the whole earth. Their distribution within shorter distances also often depends largely upon it. In the United States, for example, the Live Oak does not grow in Maine, nor the Canoe Birch in Flor- ida. Even the op- posite sides of the same hill may be covered with two different species, be- cause one of them resists the late and earlv frosts and the fierce midday heat of summer, while the other requires the coolness and moisture of the northern slope. (See fig. 24.) On eastern slopes, where the sun strikes early in the day, frosts in the spring and fall are far more apt to kill the young trees, or the blossoms and twigs of older ones, than on those which face to the west and north, where growth begins later in the spring, and where rapid thawing, which does more harm than the freez- ing itself, is less likely to take x)lace. REQUIREMENTS OF TREES FOR HEAT AND MOISTURE. Heat and moisture act together upon trees in such a way that it is sometimes hard to distinguish their. Fig. 23.—a forest of Palms in southern Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Division of Forestry. Washington : G. P. O.


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