Fig. 71. Long-bodied White Oak of the Forest. U. S. Forest Service.

Even the trees most tolerant of shade in youth, like spruce, must have light later or perish, and hence in a forest there is the constant upward reach. This produces the characteristic "long-bodied" trunk of the forest tree, Fig. 71, in contrast to the "short-bodied" tree of the open, where the branches reach out in all directions, Fig. 72. In this constant struggle for existence is involved the persistent attempt of scattered seeds to sprout whenever there is an opening. The result is that a typical forest is one in which all sizes and ages of trees grow together. Scattered among these are bushes and scrubby trees, called "forest weeds," such as mountain maple and dogwood, Fig. 80, [p. 233], which do not produce timber.

Fig. 72. Short-bodied White Oak of the Open. Fort Lee, N. J.

By foresters the trees themselves are classified according to their size into:

Every age has its own dangers. Many seeds never germinate, many seedlings perish because they do not reach soil, or are killed by too much or too little moisture, or by heat or cold, or shade. At the sapling age, the side branches begin to interfere with those of other saplings. Buds are bruised and lower branches broken by thrashing in the wind, and their leaves have less light. Only the upper branches have room and light, and they flourish at the expense of lower ones, which gradually die and are thus pruned off. Some trees naturally grow faster than others, and they attain additional light and room to spread laterally, thus overtopping others which are suppressed and finally killed, beaten in the race for life.

If the growth should remain about even so that the trees grew densely packed together, the whole group would be likely to be of a poorer quality, but ordinarily the few outgrow the many and they are called dominant trees. Even then, they still have to struggle against their neighbors, and at this, the large sapling stage, many perish, and of those that survive there are great differences in size. Trees make their most rapid growth in height, and lay on the widest yearly "rings," at the large sapling and small pole age, Fig. 114, [p. 263]. It is at this stage, too, if the growth is at all dense, that the young trees (poles) clean themselves most thoroly of their branches. The growth in diameter continues to the end of the tree's life, long after the height growth has ceased.