National
Forest
Inventory

homepage

Executive summary
General information
History
Materials
Methods
Results
Resources
Expertise
Products
Publications
Applications of results

Current events/projects
Use of SAR (radar) data
Imaging spectrometry
Dynamics of biodiversity
[Finnish]
METLA
METLA Research

MULTI-SOURCE NATIONAL FOREST INVENTORY OF FINLAND, HISTORY

FINLAND's FORESTS BEFORE 1900's

Slash-and-burn agriculture, burning of wood to make tar, household use of timber, ship building and, from the second half of nineteenth century, an increasing forest industry exhausted finnish forest resources. The further growth of forest industries into a large-scale one in 1870s and the reaching of cuttings deeper into wilderness forests stimulated the interest in forest resources. According to the pre-inventory documents, the forest resources of Finland were at their lowest level when raising of crops on burnt-over clearings ended, around at the turn of the century.

OLD INVENTORIES

The National Forest Inventory of Finland (NFI) has produced large-area forest resource information for over 70 years. The traditional role has been to produce objective and up-to-date information of the forest resources, forest health conditions and their development for national and regional decision making. The information has been utilized in large area forest management planning, in making decisions concerning forest industry investments and as a basis for forest income taxation. NFI covers all forests and the information has also been used by all ownership groups for justifying and calibrating their own standlevel inventory results.

The sampling system of the First National Inventory (1921-24) was line survey sampling, (Ilvessalo 1927). The methods in the following second (1936-38), third (1951-53) and fourth inventories (1960-63) were almost the same as in the first inventory, except the sampling density.

Detached L -shaped clusters have been employed instead of continuous lines since the fifth inventory (Kuusela and Salminen 1969). This design is statistically more effective and was also favoured by improved road network. At the same time, inventory work was carried out each year and proceeded by regions from south to north. Fixed size sample plots were also changed to Bitterlich plots.

The use of aerial photographs in North Finland was introduced for the first time in the 5th and continued in the 6th and 7th inventories (Poso 1972).

RECENT MULTI-SOURCE NATIONAL FOREST INVENTORY OF FINLAND

The Finnish Forest Research Institute started to develop a new inventory system in 1989, during the eight inventory, in order to obtain geographically localized, up-to-date information and for areas smaller than earlier. Sampling design and sample plot measurements have been changed to some extent. One fifth of the sample plots have been made permanent. The method exploits satellite image data, digital map data (arable land, roads, built up areas, didital terrain model) and, in the future, other geographical data, e.g. soil and meteorological data, in addition to the ground measurements. Image analysis methods have been chosen in such a way that estimates of all variables of the inventory can be computed for each pixel.

The system is now operative. The inventory results for the whole country involving theme maps and statistics for large and small areas will be ready during 1995. Statistics for a forest holding level will be available to order.

The new field sampling system has been applied from the summer of 1992, north from the administrative border of North Finland. The sampling unit is still a cluster. The distance between two clusters varies from south to north and is 7 kilometres in north-south and east-west directions in southern part of north Finland. One tract has 15 sample plots, of which three are permanent and the other twelve temporary. The coordinates of the trees on permanent plots are registered in order to identify the trees during the next inventory. %The new sampling design is shown in Figure 1, Appendix 1.

The sample plot is still a Bitterlich plot. Tallied trees are selected with a relascope, the relascopic factor varies by region, from south to north and west to east, depending on the density of the forests and has varied from 1.5 to 2 in North Finland. The maximum radius is 12.45 metres (corresponding to the bh -diameter 30.5 cm with the factor 1.5). Reducing the radius of a sample plot decreases the reliability of the estimates very little, but decreases in some cases the amount of field work noticeably, because the number of divided sample plots decreases. Every 7th tally tree is measured as a sample tree.

A new feature is a small fixed radius sample plot for small trees, i.e. trees not included in the Bitterlich plot. On forest land, those trees which will remain until the first thinning are counted.

A lot of information other than growing stock and increment is collected in National Forest Inventories. Examples are information on forest health and ground vegetation, animal observations in some inventories for estimating species distribution, and bryophyte samples for analysing the distribution and concentrations of sulphur and heavy metals, etc.

During the season 1995, the grid of permanent 3000 sample plots, established for forest health monitoring purposes 1985-86, will be measured the third time. The nineth inventory will start 1996. New features will be the measurement of some additional characteristics describing forest biodiversity.

Ongoing research topics in the inventory are testing of radar data (ERS-1 SAR, RADARSAT) and the introduction of airborne imaging spectrometer into the system. Methods for monitoring biodiversity of forests are being developed.

References

Ilvessalo, Y. 1927. The Forests of Suomi (Finland). Results of the general survey of the forests of the country carried out during the years 1921-1924. Communicationes Ex Instituto Quaestionum Forestalium Finlandiae. Editae 11.
Kuusela, K. & Salminen, S. 1969. The 5th National Forest Inventory in Finland. General design, instructions for field work and data processing. Commun. Inst. For. Fenn. 69.4.1-72.
Poso, S. 1972. A method for combining photo and field samples in forest inventory. Commun. Inst. For. Fenn. 76(1):1-133.
Tomppo, E. 1993. Multi-Source National Forest Inventory of Finland. Proceedings of Ilvessalo Symposium on National Forest Inventories. Finland 17-21 August, 1992. IUFRO S4.02. The Finnish Forest Research Institute. Research Papers 444. pp. 52-60.

VKan, December 2000