Increment and drain (3.1)
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Figure 3.1 Annual increment
of growing stock (1935–2010)
and annual drain (1950–2010).
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The balance between annual increment and drain of growing
stock12 is the principal indicator of the sustainability of wood
production. The total drain may not exceed the increment in
the long term.
In the National Forest Inventories, the increment of stock is
measured for increment estimation periods, which comprise
the preceding five growing seasons. One of the reasons for using
5-year periods is to reduce the effect of annual variation
on the estimation due to such factors as weather, for instance.
There is, therefore, a temporal difference between figures for
increment and drain.
The annual increment of growing stock has exceeded the total
drain by one fourth on average since the mid-1970s. The balance
between increment and drain varies between tree species
and by region. According to the latest forest inventory (NFI 11),
the annual increment in 2009–2010 and was 103,7 million cubic
metres. The annual drain has been 68 million cubic metres on average
in the 2000s. The growing stock has continuously increased in
volume since the 1970s (see indicator 1.2).
Links
12 The total drain consists of roundwood removals (=commercial roundwood
felled for industry and exports, firewood used by small residential houses, and
wood for contract sawing), logging residue left in the forest (slash) and the residue
of naturally died trees (natural drain). The amount of logging residue left in
the forest varies annually depending on the roundwood removals. In 2010 the
amount of logging residue accounted to 8,4 million m<sup>3</sup> and the natural drain
to 4,7 million m<sup>3</sup> or 7% of the total drain.
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