58 FOREST REPORT 2005
3.1 Timber increment and timber use
In Switzerland the mean annual increment (i.e. new growth) is 9.2 m
3per hectare of forest.
The increment provides enough timber to build 130000 family homes.
Trees are growing faster today because more nitrogen is taken up by forest soils where it acts as a fertiliser, and because the climate has become warmer in recent decades.
For decades timber increments in Swiss forests have exceeded harvesting by some 30%.
More growth and underuse
Trees grow, add year rings, and get taller and thicker. Between 1985and1995Swiss forestspro- duced nearly 10 million cu- bic metres of timber annually,a quantity large enough to build 130 000 family homes.Moreover, according to surveyscarriedout in Canton Bern and in several centralEuropeancountries, trees havebeen growing faster.Possi- ble causes under discussion are global warming, higher carbon dioxideconcentrations in theat- mosphere and nitrogen deposi- tion from the air. The nitrogen, which mostly comes from agri- cultureand traffic,actsasaferti- liserand accelerates tree growth.
Trees grow faster in soils with higher nutrients levels and in warmer and more humid cli- mates.This explains regionaldif- ferences in timber increments.
Annual gross increments be- tween 1985 and 1995 averaged 9.2 m3/ha for Switzerland as a whole, but were 13.9 m3/ha in theSwissCentralPlateau,6.4m3 in the northernAlps,and amere 5m3 in the southernAlps.Swit- zerlandranks first amongallEu- ropean countries with respect not only to annual increments but also to growing stock.
Conifers account for two thirds of the timber increments in Switzerland and broadleaf trees one third.Norway spruce(Picea abies) alone is responsible for 44% of the total increment, Eu- ropean silver fir (Abies alba)for 16%and beech (Fagus sylvatica) for20%.These three tree species make up80%of both the grow- ing stockand the increment.
For structural reasons Swiss forestry can only use 70%of the annual increment (> 6 Social Economy), which is why there has been a steady increase in growing stock (> Indicator 1.2).
While a respectable 81% of the increment is usedin theCentral
59 3USE
Forests in the Central Plateau and in the Pre-Alps are used most inten- sively because they are generally more easily accessible than those in the Alps and in the Jura, where timber harvesting is more labour-inten- sive and expensive.
FURTHER INFORMATION Swiss Federal Research Institute WSL 8903 Birmensdorf
Research Dept. FOREST Section Silvicultural strategies (0) 44/ 739 24 86
Research Dept. LANDSCAPE Section Landscape inventories (0) 44/ 739 23 43
[million m3]
3.1.1
Timber use
Annual timber usein millions of cubic metres.
«Vivian»
«Lothar»
10 8 6 4 2
0 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02
3.1.2
Underuse
Differences between thetimber increment and timber usein thedifferent forestry regions and in thewholeof Switzerland.
Data in cubic metres per hectare.
[m3/ha]
16 14 12 10 8 6 4 2
0 Jura Central Pre-Alps Alps South of Switzerland
Plateau the Alps
■increment
■use Plateau,only 40% is usedsouth
of theAlps.
Four to five million cu- bicmetres of timber are used in Switzerland each year. This fig- ure has remained the same since 1984, with temporary increases following storms such as Vivian (1990) and Lothar (1999). Coni- fers make up73%of this timber.
Forests in theCentralPlateau and in thePre-Alpsare usedmost in- tensively (41%and27%of total use, respectively) because they are generally more easily accessi- ble than those in theAlpsandin the Jura, where timber harvest- ing is more labour-intensiveand expensive. Moreover, increment rates in the Central Plateau are aboveaverage.
