TIMBER FARMING IN ARIZONA

TIMBER FARMING IN

Timber, along with minerals, soil, water, and grass, is one of Arizona's great natural resources. About one-third of the area of the State is covered by forest of which, however, the greater portion is of the low-growing type called "woodland." Tall timber is found on approximately 5 million acres, mainly on high mesas and mountain slopes above an altitude of 6,000 feet. During the past half century Arizona mills have sawed millions of trees into billions of board feet of lumber, but the forests remain largely unimpaired. Although some lands have been cut too heavily, all but relatively small areas are still productive.

Timber is a crop capable of renewal by growth. Managed as a crop, Arizona forests can be made to yield tree products perpetually in larger volume than in the past. Long before Arizona acquired statehood, the federal government took steps to safeguard her timber resources. Today, some 4 million acres of saw-timber land in national forests and Indian reservations are under management for continuous production. Ninety percent of this timber is ponderosa pine, rated as one of the best lumber trees in the United States.

Forestry is more than conservation; it is also dynamic production. In Arizona, forestry must anticipate increasing demands from new uses and from a growing population at home and in other States less generally endowed with timber resources. In order to meet this increasing drain forestry must improve yields in both volume and quality. Henceforth, it must produce sawlogs in half the time nature has taken in the past. Foresters accept this challenge, in full confidence of the possibilities of intensive management and the promise of further advances through research.

Foreseeing many technical problems, the United States Forest Service in 1909 created what is now the Fort Valley Experimental Forest which is in fact an experimental farm in which timber is the main crop. Timber crops are harvested and regrown, and some of the lands have already been logged a second time. An indispensable feature of these operations are permanent records of some 40,-000 trees on 9 areas varying in size from 80 acres to 480 acres and embracing a wide range of physical conditions. Every tree is numbered and all are measured at 5-year intervals. Most of these records have been going 30 years. They furnish information on the behavior of trees of all ages and sizes on different sites and under many kinds of treat-ment.

The essence of timber farming in the Southwest is this: The forests are a mixture of trees of all ages and sizes occurring mostly in small even-aged groups. By periodic removal of only the oldest and largest trees plus any that may be declining through disease or injury, the forest is kept perpetually young and the land is never denuded. When old trees have been cropped their ranks must be filled by new ones, and the young generation must be trained to develop the desired form. Nature normally performs these functions but under disturbing human influences the results are uncertain and therefore, to insure success, man must lend a helping hand.

Logging in a virgin forest removes only about half the volume. The trees cut are mainly the largest and oldest individuals plus those below par as to health and form. Remaining trees range through all age classes including not a few veterans up to 30 inches in diameter. The latter class, though perhaps 300 years old, are still capable of good growth when given freedom to extend their roots without encountering too much competition from neighboring trees. It is they that yield the most valuable lumber. Removal of additional large trees at intervals of about 20 years will provide more room for those remaining. Meanwhile small trees grow into large ones and seedlings creep in around the stumps to start a new generation.

A few immature trees are also removed, especially when they occur in dense groups. Cutting in such groups aims at the double objective of stimulating growth and improving quality. Boards of the highest quality come only from logs relatively free of limbs or knots. Trees standing in more or less open situations or on the border of a group in early life develop coarse branches which persist even after the crown canopy has closed by the encroachment of neighboring trees; in contrast, those subjected to side shade from close neighbors in early life go through the process called natural pruning. In natural pruning the lower limbs, sometimes to a height of 30 feet, die and fall off, leaving what foresters call a clean bole. Natural pruning is seldom perfect, but if it removes most of the branches the timber farmer can cut off the remaining ones at relatively low cost. If a group contains more trees than the soil can support in vigorous condition, it

ARIZONA

is good silviculture to favor the smaller clean-boled ones by harvesting at the first opportunity the limby ones which usually are also the largest. A remarkable characteristic of ponderosa pine is that it may stand in a dense group for a hundred years, growing almost imperceptibly, and then spring into rapid growth when competing neighbors are cut.

Restocking is always a matter of concern. We seldom plant in the Southwest because the operation is expensive. Instead, we rely on nature to do the planting by means of self-sown seed. Nature bides her time and if all conditions are not favorable many decades may be required. Forestry in Arizona is confronted by the task of not only replacing trees that are cut but also of restocking large openings which for various reasons may have remained bare of seedlings for 50 years or more. Efforts in this direction have been fairly successful, as attested by thousands of acres now bearing fine stands of young trees which have started in the past 30 years. Dense stocking is desirable in order to induce the development of straight stems with fine branches susceptible to natural pruning.

As soon as the members of juvenile stands attain sufficient size to be used for poles, mine props or sawlogs, it is desirable to cut out one here and there where they are too close together for good growth. Crooked, extremely limby, or otherwise undesirable trees can be eliminated cheaply by introducing a small quantity of sodium arsenite solution in the trunk. This practice is especially commendable where a worthless tree is dominating smaller ones of good form.

Hand pruning is beneficial when young stands are not dense enough to promote natural pruning. Open-growth trees grow rapidly but are of little value for lumber unless the coarse lower limbs are cut off while the bole is small in diameter. After the pruning scars have healed, the layers of wood deposited by each year's growth are free of knots. A man equipped with a curved saw mounted on a 12-foot pole can remove the branches to a height of 17 feet. Allowing 1 foot for the stump, this provides for a clear log of standard 16-foot length. Usually it is not considered practical to prune higher than 17 feet; but the first log contains nearly half the volume of the tree.

Extremely broad, low-branching trees are called wolf trees. Like the wolf of forest lore, they live by destroying their neighbors. Wolf trees grow to enormous size, often suppressing all plant life within a radius of 50 feet; but they themselves are next to valueless for lumber. Taken in hand while still young their abnormal characteristics can often be corrected by pruning; but after passing a bole diameter of about 16 inches they are better eliminated. If felled they smash down large numbers of small trees, and the mass of branches must be piled and burned as a safeguard against fire. A more economical method is to kill the wolf tree and let it disintegrate slowly. Sodium arsenite solution applied in holes bored in the trunk with an ordinary brace and bit causes death in 2 or 3 weeks.

BY G. A. PEARSON*

trees grow to enormous size, often suppressing all plant life within a radius of 50 feet; but they themselves are next to valueless for lumber. Taken in hand while still young their abnormal characteristics can often be corrected by pruning; but after passing a bole diameter of about 16 inches they are better eliminated. If felled they smash down large numbers of small trees, and the mass of branches must be piled and burned as a safeguard against fire. A more economical method is to kill the wolf tree and let it disintegrate slowly. Sodium arsenite solution applied in holes bored in the trunk with an ordinary brace and bit causes death in 2 or 3 weeks.

The collective operation of thinning, pruning, and removal of worthless trees is called improvement. The term needs no further definition. The sole purpose is improvement of the stand.

Mistletoe is a parasitic plant growth which attacks nearly all kinds of trees, but there is a separate mistletoe for each tree species. The one found on ponderosa pine is known to botanists as Rhazoumofskya cryptopoda. It may be recognized as a mass of yellowishgreen stems about 6 inches long, without leaves, usually attached to the branches which under its influence tend to become distorted into odd shapes. The pine mistletoe is a killer devoid of the beauty and romantic traditions associated with some of its kin. It is no respecter of age or class, for it kills or deforms trees from the sapling stage to maturity. Mistletoe is common on more than half of the ponderosa pine area in Arizona and where it occurs it reduces the net growth by an estimated 25 percent. Although complete eradication is scarcely possible, the parasite can be held in control by directing logging operations and stand improvement to that end.

Fire, the universal forest enemy, is now being fairly well controlled through organized detection and supression in the national forests, the Indian reservations and the national parks. The critical fire season, occurring during the dry windy period of June and early July, is usually terminated by the summer rains beginning in July; exceptions occur in years when the rains are deferred or of subnormal volume.