Indicator forest and wood

Wood harvesting/net increment ratio

The annual wood increment is contrasted with wood removals. To ensure sustainable forest management, the balance between the increment, i.e. wood growth, and removals, i.e. logged and dying wood, as measured by tree generations, must be maintained over the longer term. While the increment changes rather slowly depending on the forest structure and climate development, removals are normally subject to short-term fluctuations. The volume of wood harvested depends primarily on the age structure of the forests, the tree species composition and the timber market. Mortality is caused by natural events such as storms, avalanches and drought combined with their associated consequences, such as insect infestation.

Assessment of the state
medium medium
Assessment of the trend
positive positive
Ratio of wood harvesting to net increment 2006 - 2013 (NFI3-NFI4b): 0.86 Ratio of wood harvesting to net increment 1995 - 2006 (NFI2-NFI3): 0.96 Ratio of wood harvesting to net increment 1985 - 1995 (NFI1-NFI2): 0.72
A value of 1 means that wood harvesting is consistent with the net increment. A value larger than 1 means that wood harvesting is higher than the net increment.

Data for the graph: Excel
Source: Swiss Federal Institute for Forest, Snow and Landscape Research: Swiss National Forestry Inventory (NFI)
Hardwood Southern Alps: 75354 Softwood Southern Alps: 76542 Hardwood Alps: 124515 Softwood Alps: 680501 Hardwood Pre-Alps: 283315 Softwood Pre-Alps: 937241 Hardwood Central Plateau: 881683 Softwood Central Plateau: 1043194 Hardwood Jura: 599585 Softwood Jura: 662184
Timber harvesting in 2016 by intended use and producing region. Survey for Swiss forestry statistics: All forest owners are surveyed on the harvested timber volume by intended use and type of wood.

Data for the graph: Excel
Source: Forestry statistics (extrapolated)
  • Database
Comment

The net increment was very much in balance with wood harvesting in the period between 2007 and 2013. From the perspective of forest management, the volume of wood harvested should match the volume of wood grown.

Clear differences in the ratio of wood increment to harvesting can be observed between the various regions of Switzerland. For instance, the increment exceeds the harvest in the Pre-Alps, Alps and Southern Alps, whereas the ratio between the two processes is balanced in the Jura. In contrast, the increment is lower than the harvest in the Central Plateau.

International comparison

To conserve and strengthen the productive functions of forests, the Ministerial Conference for the Protection of Forests in Europe (Forest Europe) postulates that a balance be maintained between the annual net increment and harvesting in forest areas that are available for wood production. The comparison of wood increment, harvesting and mortality reflects this postulate.

Method

Net increment and wood harvesting data are provided by aerial images, the continuous sample survey carried out in forests and subsequent modelling. To calculate the ratio, harvesting is divided by net increment.

Definition of increment (net growth): annual increase in the stemwood volume of all trees (with ingrowth) minus annual mortality.

Definition of harvesting (wood harvesting): stemwood volume of all trees harvested between two consecutive forest inventories. While wood harvesting is based on figures from the National Forest Inventory, timber harvesting figures come from forestry statistics.

Definition of mortality: stemwood volume of all trees that died or disappeared naturally between two consecutive inventories.

Evaluation unit: The increment is measured on the basis of the forest area (accessible forest without brushwood) according to the NFI1 inventory. The assessment is based on the network (list items) according to NFI4 (2009-2013).

For the 1985-1995 (NFI1-NFI2) period, only data on the ratio between removals (harvesting and mortality) and the increment are available.

 
Last updated on: 27.11.2018

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