Comparison of the growing stock increment and drain (forest balance) shows whether the stemwood stock in forests is growing, remains unchanged or is decreasing. The volume is expressed in millions of solid cubic metres with bark.
The latest data on the growing stock increment are based on the National Forest Inventory (NFI12, measurement years 2014−2016), performed by the Natural Resources Institute Finland. The Finnish Forest Research Institute started the National Forest Inventories at the beginning of the 1920s. The NFI data are sample data that cover the entire country. According to the current system, each inventory measures around 53,000 sample plots and about one million trees on forest land and poorly productive forest land over a five-year period.
The estimate of the drain in the growing stock was based on wood consumption studies until 1984, and since then has used annual removal and wood consumption statistics. In addition to felled stemwood, the drain in the growing stock drain also includes stemwood waste left in forests, and natural losses.
Natural Resources Institute Finland: National Forest Inventory (NFI) and Statistical Services