Increases above the protective limit are allowed only to purchasers of stock and ranches of permit holders and any such increase must not exceed the maximum limit. Class A permittees owning a less number of stock than the protective limit are allowed to increase their number gradually. Whenever it is found necessary to reduce the number of stock allowed in any National Forest, Class C stock is excluded before the other classes are reduced. The reduction on a sliding scale is then applied to Class B owners. Class A owners are exempt from reduction. When new stock owners are allowed the use of National Forest range upon a Forest already fully stocked, reductions in the number of permitted stock of Class B and C owners is made in order to make room for the new man. Thus it is seen that the matter of protective limits is actually a protection to the small stock owner; he is protected from the monopoly of the range by big corporations. When necessary to prevent monopoly of the range by large stock owners, the District Forester establishes maximum limits in the number of stock for which a permit may be issued to any one person, firm or corporation. _Prohibition of Grazing._ It often becomes necessary to prohibit all grazing on an area within a National Forest or at least to materially reduce the amount of stock which is allowed to graze on a given area. Sheep may be excluded from a timber-sale area for a certain number of years after cutting or until the reproduction has become well established. Where planting operations are being carried on it is usually necessary to exclude all classes of stock. If investigations show that grazing is responsible for the lack of reproduction over a considerable area, the area or a portion of it may be withdrawn from range use until young growth has become established again. The watersheds of streams supplying water for irrigation, municipal or domestic purposes may be closed to grazing of any or all kinds of domestic stock when necessary to prevent erosion and floods or diminution in water supply. Camping grounds required for the accommodation of the public may be closed to the grazing of permitted stock. Limited areas which are the natural breeding or feeding grounds of game animals or birds may be closed to grazing. Areas within National Forests infested seriously by poisonous plants may be closed to grazing. _Protection of Grazing Interests._ The protection of National Forest grazing interests is secured by the prevention of overgrazing, by the prevention of damage to roads, trails, or water sources, by the proper bedding of sheep and goats, by the proper disposition of carcasses, by salting the stock and by the proper observation of the national and state live stock and quarantine laws.