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Sustainable forestry

2007 Schools Wikipedia Selection. Related subjects: Environment

   Sustainable forestry is a forest management concept. The basic tenet of
   sustainable forestry is that the amount of goods and services yielded
   from a forest should be at a level the forest is capable of producing
   without degradation of the soil, watershed features or seed source for
   the future. It differs from Sustained Yield Forestry and Sustainable
   forest management according to the sets of forest goods and services
   that we attempt to "sustain".

   Sustainable forestry includes, clean water,wildlife, recreation natural
   cover and forest where seed trees are left for natural regeneration.
   The sensitive ecosystems are not all about the tall trees but rather
   the whole mosaic of forest entities. The potential natural vegetation,
   annual growth and the basal area, combined with the amount of trees per
   stand to develop a management plan for area sizes from a stand to an
   ownership through the entire forest, as well as considering the
   landscape and position of the forest within it are considered.

Boreal forests

   In boreal forest and other forests, clear cutting and intensive
   silviculture have been blamed for biodiversity problems. Many
   environmentalists believe that clearcutting is not sustainable, while
   single tree management is. Many foresters assume that in boreal
   situations clear cutting imitates natural forest fire and other
   dynamics in important ways. Recent research has suggested that
   large-scale fires did not occur very frequently and that the end result
   of fire or other natural dynamics are not comparable with the end
   result of clear cutting. However, considering that boreal forests have
   low biodiversity to begin with, these claims may be unsubstantiated.

   Clearcutting and other types of even-aged forest management are used as
   silvicultural tools to promote growth of shade-intolerant species and
   are used in some forest types in order to promote regeneration. Levels
   of spatial patchiness (horizontal structural diversity) at the expense
   of variety of canopy layers (vertical structural diversity), both
   necessary for many wildlife species, are increased with some level of
   even-aged management. Selection system, or uneven-aged forest
   management, has low levels of horizontal structural diversity with a
   high level of vertical structural diversity. Thus it seems that both
   types of management should be considered at the landscape level.

Old Growth Forests

   If sustainable forestry is an experiment, reserves are the control of
   that experiment. By comparing a management regime to a close to natural
   setting, we can better devise schemes for optimal growth. Aside from
   being a good standard to compare our commercial forests to, old growth
   forests are a good seed source. The two-hundred year old trees in old
   growth forests are not representative of all the trees two hundred
   years ago- they are actually the most resilient trees of their time.
   The old trees are the trees that made it, while others did not- those
   trees are more disease resistant, fire resistant and fit than any
   other.

High grading

   One ecological advantage of clearcutting is that it avoids the risk of
   selection cutting and single tree management. When harvesting
   individual trees from a stand, some jurisdictions consider it
   sustainable practice to cut the tallest, fastest growing and generally
   best trees. This ' high grading' leaves the dwarfed, non preferred
   trees to make up the gene pool of the forest. The result is a short,
   poor growing forest, especially when there is a lack of an outside seed
   source. High grading has long been discredited in some jurisdictions,
   such as Canada, where any recent examples would be rare.

Fire suppression

   Fire and insect infestations are the dominant natural disturbances in
   the Taiga and is an important disturbance mechanism in many other
   forest types, including temperate, sub-alpine and chaparral forests.
   Large, stand-replacing fires, particularly in the boreal forest,
   determine the age distribution and spatial age mosaic of the forested
   landscape.

   In North America, the belief that fire suppression has substantially
   reduced the average annual area burned is widely held by resource
   managers and is often thought to be self-evident. Direct empirical
   evidence however is essentially limited to just two studies by Stocks
   (1991) and Ward and Tithecott (1993), that use Ontario government fire
   records to make comparisons of average annual area burned between areas
   with and without aggressive fire suppression policies. Numerous
   subsequent studies have presented the same information, often in a
   different format (Martell 1994, Martell 1996, Weber & Stocks 1998, Li
   2000, Ward & Mawdsley 2000). The proponents of these studies argue that
   areas without aggressive fire suppression policies have larger average
   fire sizes and greater average annual area burned and a longer interval
   between fires and that this is evidence of the effect of fire
   suppression.

   However, the idea that fire suppression can effectively reduce the
   average annual area burned is the focus of a vocal debate in the
   scientific literature. In particular, several recent papers have argued
   against this idea (Miyanishi & Johnson 2001, Miyanishi et al. 2002,
   Bridge et al 2005). These papers claim that statistically rigorous
   techniques for estimating the average annual area burned, called the
   fire cycle, do not show changes in the fire cycle associated with fire
   suppression and that the evidence used to support the effect of fire
   suppression is biased and has been presented in a way that is flawed.
   Note that none of these papers criticize fire management agencies for
   being anything less than completely committed to their mandate. Nor do
   they suggest that fire personnel are not well trained, efficiently
   deployed or well managed. Instead, these papers simply suggest that
   despite the resources employed, fire management agencies are simply
   unable to effectively reduce the average annual are burned.

   The impact that effective fire suppression may have on the average
   annual area burned is important for many reasons, but in particular,
   its impact is key to the current paradigm of sustainable forest
   management in many jurisdictions. One of the core aspects of SFM in
   many jurisdictions is the use of wood supply models to determine
   sustainable harvest levels. This determination of sustainable harvest
   levels often assumes that fire suppression has been effective at
   reducing the average annual area burned. Thus, if current assumptions
   about the effect of fire suppression are wrong, the impact on SFM could
   be substantial.

   One area where it is largely accepted that fire suppression has altered
   the “natural” fire regime is the Pinus ponderosa ecosystems in the
   interior West of the United States, where a historical regime of
   frequent surface fires had maintained open-canopy conditions. With the
   arrival of European settlers, the frequency of surface fires decreased,
   changing both the accumulation and arrangement of fine fuel. Growth of
   an intermediate-height ladder of vegetation and the increased bulk
   density of canopy fuel allowed surface fires to burn into the crown,
   thus creating a crown-fire regime (Fuli et al. 1997, Shinnerman & Baker
   1997).

Harvest

   Harvest of trees can deplete nutrients in forest with poor soil. This
   is particularly true with whole tree harvest as many nutrients are held
   in the tops and branchs. Harvest often doesn't allow for different
   successional stages. Forests have different stages of height, age and
   species diversity, and different animals depend on each. Some harvest
   techniques eliminate one or more stage of forest development, reducing
   the value of the wildlife in the forest, and reducing the health of the
   trees overall.

   There are six different kinds of tree harvesting:

   Selective cutting, Shelterwood Cutting, Seed-Tree Cutting,
   Clear-Cutting, Strip Cutting,

Fragmentation

   Urban sprawl and other construction can fragment forests. This creates
   edge habitat, habitat not protected by other trees and exposed to an
   urban environment. If the same area of forest is spread over different
   fragments, than there will be more edge than if all of that area were
   in one lump. If that same area is in a narrow line, then all of the
   forest becomes the degraded edge with little or no middle. Edge trees
   are not protected from storm wind, and are more easily consumed by
   deer. The wildlife living along the edge will suffer predation by
   racoons or may simply leave because the species will not live that
   close to humans. There is also the problem of dispersal between
   fragments. If a part of a contiguous stand of trees is damaged, it can
   be repopulated by the existing trees around it. However if that stand
   happened to be a part of a fragment with no dispersal from the rest of
   the fragmented area, it would take human intervention to maintain the
   stands. Wildlife species with poor dispersal would suffer in this
   situation also, even including some birds that will very rarely fly
   over highways.

Solutions

   Using untouched reserves as a model, we can try to recreate those
   forest conditions. Selection cutting is a practice which mimics some
   natural disturbances like a tree falling down. Clearcutting mimics
   other natural disturbances such as intense forest fires. If we can
   mimic natural conditions, trees have been evolving to grow well under
   those conditions far longer than under modern forestry conditions, and
   our mimicry will yield better trees. Selection cutting can be based on
   gap sizes and woody debris found in our natural reserves. Sustainable
   forestry also involves re-introducing fire to forests. This has the
   added benefit of bringing back a variety of wildlife species. And there
   are also harvest practices that can allow all successional stages of a
   forest to exist.

   Dispersal corridors are lines of habitat that go between fragments so
   that beneficial wildlife can travel at a regualar rate between forests.
   This helps lichens and poor dispersing plants and animals to survive in
   between forest fragments. However, this does not reduce edge effects or
   help protect trees from the wind. It can help the trees cross pollinate
   and expand their gene pool, however.

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