How does this work? The Forest Service ranger, to begin with, must understand the surroundings in which specific trees are born from their seeds and the conditions which produce their best growth. He must also be familiar with society’s use and needs for timber-type trees. These constitute two general classes: Softwoods or conifers, the mostly evergreen cone bearers; and the hardwoods or broadleaf trees, of which most are deciduous, that is, shed their foliage in the fall.
Among the conifers are pine, fir, spruce, redwood, and hemlock. Conifers, the oldest of tree families, were widespread on the face of the earth millions of years ago. The somber giant sequoias still stand as living history pre-dating the birth of Jesus. Bristlecone pines have been found that range from 4,000 to 4,600 years old. Conifers are the main strength of America’s timber resources, providing four-fifths of the large sawtimber trees. The conifer is called softwood and is used extensively in construction and fiber for paper pulp.
Broadleaf trees include oaks, maples, elms, and sycamore. Their wood is used in furniture, among other purposes, and together they are called hardwoods (although a few are softer than some softwoods).
The forest manager knows that deciduous trees require some moisture throughout the year, while conifers can survive where it is concentrated mostly in winter snowfall. But this is only the start, for there is also the magic of tree seeds to fathom, interpret, and adapt.
Seeds range in weight from the heavy, large black walnut down to specks almost as fine as sand. Some are borne on wings, so remarkably balanced that they ride the winds for miles. Some are sown only by birds and other animals—if not consumed by them first! Many trees produce seeds every year, others less often or irregularly. Of every 100 seeds reaching the ground, only a few may sprout. And the cones of some trees, like jack pine in the Lake States (sometimes called fire pine), and knobcone pine in the West, are opened and their seeds prepared for germination by fire.
The forest manager must reckon with seed behavior and the complex conditions required for seeds to take root and reproduce the forest. Some are best allowed to seed naturally from mature parent trees. Others are best sown by hand or by airplane. Millions of seedlings are grown in National Forest nurseries and are planted in the forest by hand and by machines. Then, once in the ground, the young trees (plantations) may require some shade to survive, freedom from competing brush, and protection from animals, insects, and fire. Providing this is called plantation care.
Forest trees are also classified by their tolerance and intolerance to shade. Sugar maple, for instance, is called a tolerant tree because it will endure as a youngster with only a minimum of sunlight under the cover of taller trees. But Douglas-fir is relatively intolerant to shade, as is black cherry.
Various silvicultural cutting practices are used to obtain the desired degree of light and to encourage seedling establishment. Cutting can alter the density of the forest canopy or overstory to enable more light to reach the forest floor. Or it can open a new bed for seed if located the proper distance from nearby uncut stands. For southern pines, such a distance is usually not over 500 feet; for red spruce, in contrast, it may be as far as 1,500 feet.