This section presents a brief description of the location and main ecological characteristics of forest ecosystems found in the temperate and boreal regions.1
Temperate forests extend from the tropics towards the poles, up until latitudes of around 50_. At lower latitudes, warm temperate forests are bounded by the continental steppes (in the Northern Hemisphere) or the subtropical forest zone. Temperate and warm temperate forests exist in both the Northern Hemisphere and the Southern Hemisphere, but there are no boreal forests in the Southern Hemisphere.
The climate of temperate forests is characterised by cold winters when it may snow (at higher latitudes) and mild and moist summers. Vegetative growth occurs for up to nine months each year in most parts of the zone.
Temperate forests often occur close to farmland and/or densely populated urban areas. Therefore, these forests are often utilised intensively as a source of recreation-related, non-forestry activities (e.g. hunting, fishing, picking mushrooms, picking fruits and berries etc.). However, temperate forests constitute an important source of industrial roundwood of the same magnitude as boreal forests. For example, the currently estimated total net increment in European temperate forests is in the order of 500 million m3/year and the gross increment for temperate forests in North America is estimated to be in the order of 800 million m3/year.
The principal forest species groups in temperate forests include: pines; oaks; beeches; and eucalypti. In contrast to boreal forests, broadleaved trees - especially oaks - often play an important role in these forests. However, there is no general characterisation of the world's temperate forests. Indeed, the temperate forests of the world contain a great variety of ecotypes. There are humid rain forest types, e.g. along the American West Coast (where conifers dominate) and in the wet southernmost parts of South America (where these forests are characterised by the presence of broadleaved notofagus species). The original tree vegetation of the forests of the north-eastern United States of America, including the Appalachian Mountains, closely resemble those of central and south-eastern Europe. Here, an abundance of broadleaved species occur, including: oak; ash; beech; elm; and maple, and softwoods like: pine; spruce; fir; and larch.
Pines tend to dominate in areas where the climate is favourable for frequent forest fires, such as in the southern states of the United States of America. Here, the rejuvenation process is similar to that of the boreal forest. Without fire, oak species tend to dominate over time, being later replaced by even more shade tolerant species such as beech and maple if the absence of fire continues. But, even where broadleaved trees dominate the natural forest, softwoods that are more or less shade tolerant generally occur in mixtures with these. In such communities with trees of uneven ages the natural regeneration process takes place in an environment containing seedlings, younger trees as well a mature ones.
In the northern temperate forest zone, softwood and hardwood species have been successfully cultivated in pure even-aged stands as commercial tree crops over long periods of time. This type of "even age-class forestry", which has replaced both the original light demanding natural temperate forests as well as the uneven-aged mixed temperate forests, is widely practised at present all over both temperate forest zones.
The boreal forest zone is the northernmost forest zone and forms a circumpolar belt of more or less closed forests growing in harsh climates between the latitudes 50_ N to 70_ N.
These forests play a very important role as a source of industrial roundwood to satisfy the world's demand for forest products. Widespread harvesting takes place in the Nordic countries, European parts of the Russian Federation, Siberia (including parts of China's Heilongjang Province) and Canada. The Alaskan boreal forests are only currently utilised for commercial forestry to a fairly small extent.
Some of the boreal forest may seem desolate but it is the home of many ethnic groups. Modern societies exist there, which share the environment with people for whom reindeer herding, hunting and fishing are of central importance for their livelihoods.
Under normal conditions, the total yearly harvest of industrial roundwood from boreal forests is around 500 million m3. This corresponds to about 37 percent of global industrial roundwood production. In terms of coniferous (i.e. softwood) industrial roundwood production, 45 percent is harvested in boreal forests.
Frost-hardy conifer species dominate in these forests, most typically: spruce; pine; larch; and fir. Broadleaved tree species, mainly poplars and birches, occur mixed with the conifers or occupying a few special sites. Of all the tree species, the spruces are the most widespread in distribution and the most characteristic of boreal forests.
During ice ages, boreal forests must retreat to more southerly latitudes. As a result of these disturbances, all organisms within boreal forest ecosystems are not only hardy enough to stand a harsh and cold climate, they have also developed an ability to migrate over vast distances. Another characteristic of boreal forests is the similarity between each other wherever they occur. The same types of trees, plants, mosses, lichens, mushrooms, fish and animals appear regardless of the continent on which they occur.
An adaptation to surviving catastrophic events is a typical feature of boreal forest ecosystems. Some catastrophic events are even important for the rejuvenation of most tree communities and the survival and health of many organisms. Due to frequent fires, the natural boreal forest ecosystem usually consists of a patchwork of tree communities having been rejuvenated after forest fires or other catastrophic events on different occasions over time.
With a few exceptions, present-day boreal forests grow on land that was previously covered with ice. One characteristic of these glaciated soils is that, except in mountainous areas or along riverbeds, they are quite resistant to erosion. Therefore, they are not very sensitive to sudden changes in the forest cover; such as occurs during natural wild fires or forest harvesting.
Boreal forests have been successfully managed under sustainable yield systems for the longest time in Northern Europe.
In summary, the boreal forest is relatively tough and flexible ecosystem. Even if it is maltreated, for example during careless forest operations, in most cases it is likely that it will resume its original form and structure over time. However, the natural process of recovery may take a century or more.
1 A forest ecosystem can be described as a biological community with interrelationships between the various trees and other organisms constituting the community and with interrelationships between these organisms and the physical environment in which they exist.
