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Age structure of forests (1.3)
The age structure of forests is an indication of the history of the
development and use of forests, and of the structure of growing
stock. The development of stand attributes is generally presented
relative to stand age. Stand age is also an important factor
in forest management planning. The aim in wood production is
an age structure which maintains a high, even and sustainable
yield. This aim can be attained with an even age structure, where
the age of the oldest stands corresponds to the recommended
rotation length. The recommended rotation length varies around
the country, being from 50 years to 150 years depending on the
species and the site.
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Figure 1.3. Age structure of forests in the 1960s and the 2000s.
Source: Finnish Forest Research Institute, National Forest Inventory |
The age structure of Finnish forests is nowadays fairly even (Fig.
1.3). Looking at the situation by tree species, however, the age
structure deviates from the recommended structure for wood
production. Stands dominated by Scots pine or broadleaves are
young, whereas those dominated by spruce are usually older. In
recent years, spruce plantings have increased notably in relation
to other tree species, and this will eventually be reflected in the
relative age structure of tree species.
The age structure of forests has changed radically since the
1920s. The percentage of middle-aged forests has decreased especially
in southern Finland, and that of old forests in northern
Finland. Owing to large nature conservation areas in the north
of Finland, however, there are a great many forests there that
are over 140 years old. In the beginning of the 20th century,
the effects of slash-and-burn agriculture and selection logging
as well as the wide area of forests outside commercial management
in Lapland were still clearly discernible. The current
age structure is the result of the rise of forest industry and its
increased need for raw materials, systematic silviculture and
changes in harvesting methods.
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