One company has recently experimented with summer broadcast burning of slash on relatively small areas of 5 to 25 acres surrounded by fire lines, on the theory that the fires would not be destructive if they did not become extensive. Study on the ground makes it clear that this, like other forms of broadcast slash burning in the yellow pine type, is disastrous in its effect on the forest. A sample strip on this area showed the following effect of summer slash fires on advance reproduction: Number of seedlings per acre before fire--- Percentage of reproduction left.. Percentage of plots with reproduction, before fire_... 12 FIG. 3.-BROADCAST BURNING OF SLASH CREATES BRUSHFIELDS Slash fires not only destroy the advance reproduction, but commonly kill many seed trees as well, leaving the land to the vigorous invasion of valueless brush species. Extreme care was taken on this area to prevent the spread of fire to virgin timber, and as a matter of fact, the cost per acre was as great as if the slash had been gathered into piles and burned. Nevertheless, the advance reproduction was nearly wiped out, as illustrated in Figures 4 and 5, and this, coupled with the clear cutting, makes the future productivity of the area very doubtful. The uncertain action of fire is illustrated by another instance, where a splendid stand of nearly pure yellow pine has followed cutting and broadcast slash burning in the mixed conifer type on a north slope. This is one of the unusual cases resulting from a rare combination of factors-good seed crop ripened before logging, fire removing competing vegetation the same season as logging, and favorable subsequent seasons. That such special conditions can not be relied on is shown by the adjacent south slope, where the same fire resulted in denudation. Several other areas showing favorable results following broadcast slash burning were found in various parts of the State, but as a percentage of the total number of areas examined they were negligible. In a wide variety of forms, with spring, summer, and fall burning, on every important type, and in the great majority of cases, broadcast burning results in leaving the land unproductive. It is only under very special conditions that broadcast burns restock completely to desirable species, regardless of the intensity of the fire. Where occasionally the damage is confined to destruction of advance reproduction and small trees, the slash is not completely consumed and fire hazard remains high. As already noted, a further disadvantage of broadcast burning is that the spread of brush is much more rapid on burned than on unburned areas logged at the same time. Clearly the method can not be used if continuous forest production is sought. PILING AND BURNING Slash may be disposed of by first piling it so that it will cover a relatively small portion of the area and then burning it, as is done generally on national forest cuttings. This method is effective for reducing fire hazard but is rather expensive. A more detailed discussion of this method will be found in the second section of the bulletin. Where the object of the owner is simply to leave cut-over lands reasonably productive, it is not certain that piling and burning is necessary. Partial disposal of slash must first be examined as an alternative. PARTIAL DISPOSAL OF SLASH By piling and burning the débris on strips, and leaving the slash elsewhere, the essentials of low cost of disposal and safety of cutover lands may be attained. In an extensive examination of cutover lands two impressive findings were the very considerable proportion of cut-over lands that escape fire with no slash disposal or protection whatever, and the rapidity with which slash on such areas disappears. This statement is not an indorsement of a laissez-faire policy for cut-over lands, but serves to indicate that a study of areas untouched by fire is just as necessary as is an examination of burned lands. The desirability and practicability of leaving part of the slash must be considered from at least three angles: (1) Most important, what can be expected in protection of lands on which slash is left, and how rapidly and completely will this slash disappear? (2) What influence will leaving of slash have on development of advance reproduction, and how will it affect the chances of obtaining new reproduction? (3) Does undisposed-of slash constitute a menace as a possible starting place for epidemics of destructive insects or fungi? The last question can be answered with a reasonable degree of certainty. The danger of serious insect epidemics starting in slash appears to be slight. Freshly cut stumps and slash are of course breeding place for such insects, but the broods normally go from stump to stump and from slash to slash, rather than from stump or slash to standing tree. It is difficult to see how any form of slash disposal, even piling and burning, could prevent attack of standing This reproduction is the result of fire protection, and means that the new crop of timber is by so many years nearer maturity. FIG. 5.-SEED TREES KILLED AND REPRODUCTION WIPED OUT The same view as Figure 4, after broadcast slash burning, tells the story of a practice that has made many thousands of acres in the California pine region unproductive, a loss to the owner, the State, and the Nation. trees by insects. Many stumps are not affected by slash fires nor are they peeled, and since slash is burned in the fall and not currently at least one generation of insects would have a chance to breed in stumps or in slash before the slash is burned. So far as insects or fungous attacks are concerned, slash may be left on the ground. Bark beetles as a rule avoid limbs and small tops which may dry out before the brood matures. The danger to living trees from fungi which destroy slash is slight. Studies under way will at some future time make it possible to define the effect on subsequent reproduction of leaving slash. Even now it is fairly certain that no pronounced trouble is due to leaving slash; and in some cases, especially in yellow pine, there is evidence that the slash is an actual aid in establishing reproduction. Some advance reproduction is, of course, bent over by undisposed-of slash, but at the worst this is only a small percentage of the total left after logging, and it is safe to say that loss from this source is no greater than that from piling and burning. The question of leaving slash then resolves itself into a study of the fire hazard, the possibility of controlling fires, the rapidity with which slash disappears naturally, the possibility of preventing fires starting, and the suppression while small of those fires that do start. In a field study of many cut-over areas of ages varying up to 47 years, the examiners noted in all cases the degree of decomposition of the slash in relation to the length of time since cutting. The period required for slash to disappear entirely is rather long, probably 20 to 25 years, but it was found that after the needles and twigs were gone, the remainder, consisting of the larger limbs, pieces of the main stem, etc., did not seriously increase the difficulty of control or the damage caused by fires. Because of the heavy snowfall in the California pine region, piles or windrows of slash are mashed down rapidly; after the needles drop, usually the second year after logging, the whole mass is flat on the ground and decomposition fairly rapid. Where slash is flattened fires are not so intense or difficult to control as in fresh slash, since the whole mass can not catch simultaneously as it does when propped up in the air. In the majority of cases it was found that, in a period of 8 to 12 years after cutting, the slash had ceased to be a special hazard. Exceptional areas varied from 5 to 15 years, and even on cuttings of 30 years or more some of the larger limbs and sections of the trunk remained. As a general working rule, however, within 10 years after cutting decay and compacting so reduce slash that special protection is unnecessary on this account alone. The argument for slash disposal rests on the well-proved fact that fires in fresh slash are very difficult to control and are extremely damaging to the remaining stand of timber. The argument for leaving slash in whole or in part is based on the facts that it ceases to be a menace in fire protection in the course of a comparatively few years, that any form of disposal unless carefully done causes material damage to the remaining stand, and that the money necessary to dispose of slash properly would provide for intensive protection of the cut-over areas. Such protection will be necessary even if slash is burned. Final decision as to the best method of slash disposal must wait upon an examination of fire-protection possibilities on cut-over lands. Leaving most of the slash and maintaining an intensive patrol is a possibility. Clearly, if most of the slash is left, and will lie for about 10 years before hazard is reduced to normal, some special protection must be provided during that period. Special patrol of danger areas, in addition to the general fire protection measures, is of demonstrated value in protecting cut-over land. OTHER METHODS OF SLASH DISPOSAL Foresters generally are agreed that no method of slash disposal now followed is necessarily the final word; and a wide variety of methods have been proposed for getting rid of the slash with the minimum damage to reproduction and seed trees and at a low cost per thousand feet of logs. Lowdermilk, in the white pine region of Idaho, has made preliminary investigations to determine the feasibility of other methods than piling and burning (9), and work of a similar nature has been done elsewhere. Under certain conditions such methods as swamper burning and spot firing of slash as it lies have proved successful and cheap. Spot firing on at least one area in Montana in a yellow pinelarch-Douglas fir type gave fine results; but where it has been tried in the yellow pine type in California, the result was destructive of advance reproduction, for the slash was thrown in with the reproduction in swamping and in clearing wheel roads. None of the various methods for current disposal of slash seem to have proved its general applicability, though there are undoubtedly great possibilities in that direction. Several methods designed to hasten natural breaking down of slash have been tried, especially in the Southwest (11). Lopping and scattering, pulling tops away from seed trees, and lopping without scattering have produced results that may be valuable under certain conditions. The hazard on cut-over lands existing immediately after logging is not reduced materially by any of these methods, however, and at most they hasten the decay of slash by only a few years. One large company in California has recently tried lopping and scattering slash. Previously the company had piled and burned slash on its own lands at an average cost of 36.6 cents a thousand board feet of lumber cut, but was not satisfied with the results because of the difficulties in burning piled slash without serious damage to advance reproduction. The cost of lopping and scattering was 3.9 cents a thousand, or, plus charges for clearing around camps and donkeys and for supervision and patrol, 7.6 cents a thousand. The suppression costs were $317 for the season. The company is well satisfied with the method so far, both from the financial and forest conservation points of view. Disposal of slash is an integral part of the problem of fire protection of cut-over lands. Until experimental work shall have gone further than it has now, it seems fair to conclude that if complete disposal of slash is considered essential, piling and burning is the method that should be depended on since it accomplishes the maximum in reducing hazard. But because, as is shown in the detailed description of this method in the later part of the bulletin, special protection is needed even after piling and burning, and because of the cost of the practice, a less expensive means of slash disposal is 74722°-26-3 |