Range and forage
Important among the broad spectrum of forest resources are the understory plants that can provide forage for grazing animals, both domestic and wild. Grazing livestock are useful to the forest manager. Dense old-growth forest or vigorous second-growth stands with closed canopies generally have sparse, low-quality forage. Large forest management units, however, generally contain extensive logged or burned areas where understory forage plants temporarily dominate the site. These areas are transitory since the tree canopies close in 10 to 20 years, but they can provide good forage until canopy closure. Cutting cycles in the managed forest and even wildfires provide a continuing grazing resource that shifts from one location to another. In addition, open meadows occurring in valley bottoms, open forests on shallow soils, and grassland balds on windswept ridge tops greatly enrich the grazing potential of the forest. Grazing fees offset the long-term investments that must be carried in renewing the forest.
Hardwood forests are more susceptible than coniferous forests to grazing damage. The current year’s growth on broad-leaved trees provides palatable forage during most seasons of the year, whereas coniferous needles are much less palatable. Uncontrolled livestock-grazing in some parts of the world has been particularly devastating to forests and is a serious problem.
In agroforestry, a practice known as silvopasture, or dehesa, specifically seeks to combine trees with forage (pasture) and livestock production. The components are structurally and functionally combined and actively managed to optimize the positive biophysical interactions between them. This form of agroforestry is a practical and low-cost means of implementing integrated land management (which seeks to reduce human impacts on land), and promotes long-term, sustainable, and renewable forest management, especially for small-scale producers.
Recreation and wildlife
From the earliest times human beings have looked to the forests for recreation. Today, recreation in forests assumes ever-growing importance with the growth of cities whose inhabitants need a change of scene, fresh air, and freedom to wander, as a relief to the stresses of industrial and commercial life. Imaginative planning is essential to ensure that people actually find what they are seeking without damage to the forest environment or conflict with the pleasures of others. The most popular outdoor recreation activities utilize forestland and include hunting and fishing, picnicking and camping, hiking, mountain climbing, driving for pleasure, boating and other water sports, winter sports, photography, and nature study. The challenge is to balance the varied demands for recreational use with the other forest uses.
For many recreationists the main attraction of the woods is the abundance of animal and plant life. The forest manager must attempt to satisfy the diverse needs of hunters and sportsmen, outdoorsmen, and preservationists. This requires a broad expertise drawing on principles from the social sciences, natural history, wildlife management, conservation, landscape design, law, and public administration, among other disciplines.
Recreation management includes visitor management as well as resource management. Reasonably accurate assessments of the type and amount of use that areas receive are important to allow for efficient allocation of budgets and employee time and to ensure that the degree of use does not cause excessive impacts on resources and thus destroy the recreational value of the site. Skillful location of roads, picnic points, parking lots, and campgrounds ensures that the great majority of visitors congregate in relatively small portions of a large forest. Visitor management for some situations can be aided by use of computer-generated simulation models.
Some types of recreation require intensive management and special amenities. Vehicular camping facilities, for example, are designed for intensive use by large numbers of people and typically provide electrical hookups, toilets, showers, picnic tables, fireplaces, garbage receptacles, directional and interpretive signs, and play areas. These features must be durable and easily maintained. Downhill ski areas are most popular when well equipped with various runs, lifts, restaurants, and lodges. Other types of recreation, such as trail hiking and cross-country skiing, demand larger tracts of land but fewer improvements. Wilderness areas afford the personal challenge and serenity of backpacking, tent camping, and canoeing.
The interpretation of what visitors see in the forests has become a growing activity of most forest services. Nature trails, guidebooks, signposts, interpretive museums, and information stations assist visitors who come to learn as well as to enjoy.
Forests contain natural habitats for a wide range of wildlife, from the elks, wolves, lynxes, and bears of northern coniferous forests to the antelopes, giraffes, elephants, monkeys, lions, and tigers of tropical savannas and jungles. Certain birds, such as pheasants, wood grouse, and quail, have high sporting value, while others are cherished for attractive song, appearance, or rarity. Many endangered species depend on forest habitats that are carefully protected by national and international laws.
Forest managers must attend to the interrelated, and sometimes directly opposed, wildlife interests of hunters, conservationists, and farmers. Obviously the same animal can present a different aspect to each group. A Bengal tiger, for example, provides a biologist with a classic example of a carnivorous beast living in harmony with a jungle environment and restraining its main prey, deer, from undue increase in numbers. But to a village peasant it is a menace to cows and goats and a threat to human safety, while a game hunter regards it as a magnificent quarry demanding skill. The needs of the forest itself require the numbers of grazing and browsing animals to be kept to a tolerable level. Otherwise renewal of tree crops becomes impossible.
Virtually every change that occurs in a forest benefits some wildlife species and harms others, though plantations of monocultures are generally poor habitats. Some wildlife species require a diversity of conditions—one type for feeding, another for nesting, and yet another for cover. Some have very specific requirements essential to their existence, whereas others have a broad range of tolerance. In any case, the life history characteristics of the species must be known in order for the resource manager to plan and implement practices necessary for the well-being of the species. Sometimes the best management involves increasing the forest edge habitat, frequented by many kinds of wildlife. Forest edge improvement may be integrated with timber harvesting and the construction of fire lanes and logging roads. Because food and cover for wildlife are often more plentiful in the early stages of forest development, retardation of succession by prescribed burning may be beneficial to wildlife. Food crops may be planted in certain areas to improve the wildlife-carrying capacity. Adjustments are often made by foresters in cutting procedures, rotation age, regeneration methods, and other practices to accommodate the food and cover needs of wildlife and fish. Certain areas may be managed exclusively for wildlife, particularly in situations where habitat for endangered species must be protected.
In virtually every country the sporting aspect of woodland wildlife management is controlled, to some degree, by general game laws, which also apply outside the forests. These laws prescribe licenses for firearms and the taking of specified birds and beasts; they usually lay down closed seasons during which certain game may not be shot and also set limits on the killing or capture of rare species. In the United States a peculiar situation exists whereby the game legislation of the separate states applies unchanged over most publicly owned forests. In other countries the forest managers are in a stronger position, since local game laws are adjusted to their particular requirements.
Watershed management and erosion control
Not only is the presence of water in soils essential to the growth of forests, but improved water yield and quality are becoming increasingly important management objectives on many forested lands. Forests and their associated soils and litter layers are excellent filters as well as sponges, and water that passes through this system is relatively pure. Forest disturbances of various kinds can speed up the movement of water from the system and, in effect, reduce the filtering action. While disturbances are inevitable, in most instances they need not contribute to poor water quality.
In mountainous territory the value of forests for watershed and erosion protection commonly exceeds their value as sources of lumber or places of recreation. The classic example is found in Switzerland and the neighbouring Alpine regions where the existence of pastoral settlements in the valley is wholly dependent on the maintenance of continuous forest cover on the foothills of the great peaks. This is combined skillfully with limited lumbering and widespread recreational use by tourists.
The guiding principle of management where erosion threatens is therefore the maintenance of continual cover. Ideally, this is achieved by single-stem harvesting; only one tree is felled at any one point, and the small gap so created is soon closed by the outward growth of its neighbours.
The progress of water, from the time of precipitation until it is returned to the atmosphere and is again ready to be precipitated, is called the hydrologic cycle. The properties of the soil plant system provide mechanisms that regulate interception, flow, and storage of water in the cycle. The water that moves downward into the soil, or infiltrates, is the difference between precipitation and the losses due to canopy interception, forest floor interception, and runoff. The amount of water stored in the soil is largely dependent on the physical properties of the soil, its depth, and the amount of water lost due to evaporation from the soil surface and transpiration from plants (evapotranspiration). Transpiration is the water absorbed by plant roots that is subsequently evaporated from their leaf surfaces. Deep forest soils have a high water-storage capacity. Unless they are very porous and drain freely, they have a water table below which the subsoil is saturated. The depth of the water table varies seasonally and is higher during periods of low evapotranspiration. Removal of the forest canopy in wet areas also raises the water table. Most tree roots need air to survive and cannot exploit soil below the water table. The drainage of land having a high water table usually increases the productivity of the forest.
When incoming precipitation exceeds the soil’s water-storage capacity, the excess water flows from the soil and can be measured as streamflow. The water yield of a forest is a measure of the balance between incoming precipitation and outflow of water as streamflow. The amount of increase in water yield depends on annual precipitation as well as the type and amount of overstory vegetation removed. As forests regrow following cutting, increases in streamflow decline as a result of increased transpirational losses. Streamflow declines are greater in areas that are restocked with conifers than in those restocked with hardwoods. This results from greater transpiration losses during the winter months from coniferous species.
Despite the uncertain balance of water gain and loss, forests offer the most desirable cover for water management strategies. Water yields are gradual, reliable, and uniform, as contrasted to the rapid flows of short duration characteristic of sparsely vegetated land. Unforested land sheds water swiftly, causing sudden rises in the rivers below. Over a large river system, such as that of the Mississippi, forests are a definite advantage since they lessen the risk of floods. They also provide conditions more favourable to fishing and navigation than does unforested land. All natural streams contain varying amounts of dissolved and suspended matter, although streams issuing from undisturbed watersheds are ordinarily of high quality. Waters from forested areas are not only low in foreign substances, but they also are relatively high in oxygen and low in temperature. Nonetheless, some deterioration of stream quality can be noted during and immediately after clear-cut harvesting, even under the best logging conditions. The potential for water-quality degradation following timber harvest may involve turbidity (suspended solids) as well as increases in temperature and nutrient content. Sediment arising from logging roads is the major water-quality problem related to forest activities in many areas.
The belief that forests increase rainfall has not been substantiated by scientific inquiry. Local effects can, however, prove substantial, particularly in semiarid regions where every millimetre of rain counts. The air above a forest, as contrasted with grassland, remains relatively cool and humid on hot days, so that showers are more frequent. Fog belts, such as those found along the Pacific seaboard of North America and around the peaks of the Canary Islands, give significant water yields through the interception of water vapour by tree foliage. The vapour condenses and falls in a process described as fog drip.