Sustainable forestry
Sustainable forestry - often relates to natural cover and forest where seed trees are left for natural regeneration. There is often powerful argument as to what is truly sustainable.
The other aspect is that usually the question of sustainability is the looking in a very narrow sense at just the timber resource - the complex ecology of the forest and its systems is usually ignored. The sensitive ecosystems are not all about the tall trees but rather the whole mosaic of forest entities.
Clear cutting is not a very sustainable way of forest management. Single tree management and other close to nature methods are truly sustainable ways. The basic of sustainable forestry is that you yield the amount of timber the forest as an ecosystem with a natural structure of both small and tall trees can bare, without degradation. In most situations this means you can yield about 25 to 35% of the standing stock. It is wise to look at the potential natural vegetation and at annual growth and of course the basal area, combined with the amount of trees per unit. Some foresters believe that in boreal situations clear cutting imitates natural forest fire and other dynamics. Recent research has proved though that these fires did not occur that often and that the end result of fire or other natural dynamics are not comparable with the end result of clear cutting. In boreal forest and other forests, clear cutting and intensive silviculture are the main reasons for biodiversity problems. Clear cutting is a lazy and ignorant way of forestry, not based on forest dynamics, but on short term profit. Also wood quality is significantly lower in intensive silviculture compared to continuous cover forest management.
Old Growth Forests
Solving sustainable forestry problems requires untouched old growth reserves. 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
High grading is the practice of cutting the tallest, fastest growing and generally best trees, and leaving the dwarfed, non prefered trees to make up the gene pool of the forest. Repeated high grading is essentially genetic control prefering stunted trees. The result is a short, poor growing forest, especially when there is a lack of an outside seed source.
Fire suppression
A major barrier to sustainable forestry is fire supression. Many species, such as the Jack Pine, require fire for germination.
Harvest
Harvest of trees can deplete nutrients, as many nutrients are held in the trees. This is especially unfortunate when considering that humans do not use the nutrients in the trees in our lumber and paper products. 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.
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 acreage of forest is spread over different fragments, than there will be more edge than if all of that acreage were in one lump. If that same acreage 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 acreage, 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 better forest conditions. Selection cutting is a practice which mimics a natural disturbance like a tree falling down. 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 is 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 inbetween 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.