Even-aged timber management is a group of forest management practices employed to achieve a nearly coeval cohort group of forest trees. [1] The practice of even-aged management is often pursued to minimize costs to loggers. In some cases, the practices of even aged timber management are frequently implicated in biodiversity loss and other ecological damage. [2] Even-aged timber management can also be beneficial to restoring natural native species succession. [3]
The first step in even aged timber management is to select a suitable stand for harvest. Trees must be of merchantable size, a desirable species, and in an area accessible to harvesting equipment. Once selected, the stand is harvested (usually using feller-bunchers, skidders, and processors). Merchantable trees (trees with boles large enough to be sold to a mill) are harvested and processed whereas unmerchantable trees (trees that are too small or of an undesirable species) are either crushed by machinery or cut to make equipment movement easier. This process is called clearcutting, and the result is a cutblock. At this stage, the forestry company is required to replant the same proportion of species that were there previous to harvest. [4] Usually, silviculture techniques are employed to ensure that species survive and grow in the proper proportion. Shade-intolerant species such as trembling aspen ( Populus tremuloides ) and marsh reedgrass ( Calamagrostis canadensis ) will thrive in the open conditions of a clearcut, outcompeting shade-tolerant species such as white spruce ( Picea glauca ). Mechanical site preparation and herbicide treatments are often applied initially to allow for adequate shade-tolerant growth. This way, the shade-tolerants are given a head start and the shade-intolerants will catch up over time once silviculture treatments are stopped, resulting in an even-aged stand of trees with little vertical stratification.
Even-aged forest management is the harvesting system of choice in many parts of the world because it is often considered to be the only method that is economically viable. Forestry operations have extremely high variable costs- per hour expenses for harvesting equipment and per kilometer expenses for log transportation compose a very large portion of the total cost to harvest a stand. Therefore, companies must obtain as much productivity as possible from their hourly equipment in order to be profitable. Uneven-aged management techniques where only certain trees are harvested, such as shelterwood systems, incur the same hourly costs while harvesting fewer trees per hour. This reality explains why in Canada, for example, 90% of forests harvested are done so by clear cut through an even-aged management system. [5]
Ecological analysis indicates that even aged timber management can produce inferior outcomes for wildlife biodiversity and abundance. [6] Some species thrive on uneven or natural forest tree distribution. For example, the wild turkey thrives when uneven heights and canopy variations exist and its numbers are diminished by even aged timber management. [7]
Depending on the ecosystem, however, some species thrive under even aged timber management. Clear cutting closely mimics the results of the most prominent natural disturbance in the boreal forest- wildfires. Certain tree species of this forest type have evolved over time to regenerate favourably in open, well-lit conditions, while others are adapted to thrive in the shade they produce. Clear cutting allows shade intolerant species, such as aspen and jack pine, to regenerate where they could not in a mature forest.
Clear cutting areas for even-aged timber management can also benefit many wildlife species. The abundance of coarse woody debris added to the forest floor is beneficial to salamander and snake species, while the release of understory shrubs provides an increase of berry-foraging opportunities for bear and songbirds. [8] In general, the immature, grassy forest regenerated after a clear cut fulfills specific habitat requirements for many species that cannot be found in mature forests. In the boreal forest, for example, wildfire has been suppressed by humans, resulting in many overmature stands. Even aged timber management restores the successional cycle and allows early successional species to recolonize immature habitat.
Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars.
Coppicing is a traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down. In a coppiced wood, which is called a copse, young tree stems are repeatedly cut down to near ground level, resulting in a stool. New growth emerges, and after a number of years, the coppiced tree is harvested, and the cycle begins anew. Pollarding is a similar process carried out at a higher level on the tree in order to prevent grazing animals from eating new shoots. Daisugi, is a similar Japanese technique.
Thinning is a term used in agricultural sciences to mean the removal of some plants, or parts of plants, to make room for the growth of others. Selective removal of parts of a plant such as branches, buds, or roots is typically known as pruning.
Silviculture is the practice of controlling the growth, composition/structure, and quality of forests to meet values and needs, specifically timber production.
An old-growth forest – also termed primary forest, virgin forest, late seral forest or primeval forest – is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. The Food and Agriculture Organization of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and the ecological processes are not significantly disturbed. More than one-third of the world’s forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem. Virgin forests are old-growth forests that have never been logged. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris.
Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with shelterwood and seed tree harvests, it is used by foresters to create certain types of forest ecosystems and to promote select species that require an abundance of sunlight or grow in large, even-age stands. Logging companies and forest-worker unions in some countries support the practice for scientific, safety and economic reasons, while detractors consider it a form of deforestation that destroys natural habitats and contributes to climate change.
Forest dynamics describes the underlying physical and biological forces that shape and change a forest ecosystem. The continuous state of change in forests can be summarized with two basic elements: disturbance and succession.
This article is the index of forestry topics.
Forest ecology is the scientific study of the interrelated patterns, processes, flora, fauna and ecosystems in forests. The management of forests is known as forestry, silviculture, and forest management. A forest ecosystem is a natural woodland unit consisting of all plants, animals, and micro-organisms in that area functioning together with all of the non-living physical (abiotic) factors of the environment.
Selection cutting, also known as selection system, is the silvicultural practice of harvesting trees in a way that moves a forest stand towards an uneven-aged or all-aged condition, or 'structure'. Using stocking models derived from the study of old growth forests, selection cutting, also known as 'selection system', or 'selection silviculture', manages the establishment, continued growth and final harvest of multiple age classes of trees within a stand. A closely related approach to forest management is Continuous Cover Forestry (CCF), which makes use of selection systems to achieve a permanently irregular stand structure.
Management of Pacific Northwest riparian forests is necessary because many of these forests have been dramatically changed from their original makeup. The primary interest in riparian forest and aquatic ecosystems under the Northwest Forest Plan (NWFP) is the need to restore stream habitat for fish populations, particularly anadromous salmonids. Some of these forests have been grazed by cattle or other livestock. The heavy hooves of these animals compact the soil. This compaction does not allow the water to be absorbed into the ground, so the water runs off into the stream carrying topsoil along the way.
Patch cuts are logging cuts too small to be considered clearcuts, and are instead considered a form of selection cut. A typical patch cut might be 2-3 tree lengths. Below a certain size, seedling regeneration advantage shifts from the shade intolerant species favored in clearcuts to the shade tolerant species favored by selection harvests.
The following outline is provided as an overview of and guide to forestry:
Variable retention is a relatively new silvicultural system that retains forest structural elements for at least one rotation in order to preserve environmental values associated with structurally complex forests.
Canada's boreal forest is a vast region comprising about one third of the circumpolar boreal forest that rings the Northern Hemisphere, mostly north of the 50th parallel. Other countries with boreal forest include Russia, which contains the majority, the United States in its northernmost state of Alaska, and the Scandinavian or Northern European countries. In Europe, the entire boreal forest is referred to as taiga, not just the northern fringe where it thins out near the tree line. The boreal region in Canada covers almost 60% of the country's land area. The Canadian boreal region spans the landscape from the most easterly part of the province of Newfoundland and Labrador to the border between the far northern Yukon and Alaska. The area is dominated by coniferous forests, particularly spruce, interspersed with vast wetlands, mostly bogs and fens. The boreal region of Canada includes eight ecozones. While the biodiversity of regions varies, each ecozone has a characteristic native flora and fauna.
Shelterwood cutting refers to the progression of forest cuttings leading to the establishment of a new generation of seedlings of a particular species or group of species without planting. This silvicultural system is normally implemented in forests that are considered mature, often after several thinnings. The desired species are usually long-lived and their seedlings would naturally tend to start under partial shade. The shelterwood system gives enough light for the desired species to establish without giving enough light for the weeds that are adapted to full sun. Once the desired species is established, subsequent cuttings give the new seedlings more light and the growing space is fully passed to the new generation.
When logging began in British Columbia, Canada, in the late 19th century, the overriding concern was to harvest timber in the most economical fashion. Reforestation, aesthetics and protection of fish and wildlife habitat were not issues of great concern.
Close to nature forestry is a management approach treating forest as an ecological system performing multiple functions. Close to nature silviculture tries to achieve the management objectives with minimum necessary human intervention aimed at accelerating the processes that nature would do by itself more slowly. It works with natural populations of trees, ongoing processes and existing structures using cognitive approach, as in the case of uneven-aged forest (Plenterwald). Its theory and practice takes forest as a self regulating ecosystem and manages it as such.
Gap dynamics refers to the pattern of plant growth that occurs following the creation of a forest gap, a local area of natural disturbance that results in an opening in the canopy of a forest. Gap dynamics are a typical characteristic of both temperate and tropical forests and have a wide variety of causes and effects on forest life.
A mixedwood stand is a forest type in which 26% to 75% of the canopy is made up of softwood trees.
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