Forest resource information is collected using a remote sensing method that utilizes sample plot measurements, laser scanning and aerial photography. The quality of the data is systematically controlled at different stages of the inventory process. Forest resource information is also constantly updated from various data sources and tree stands are grown using growth models. The accuracy of the information used in the update contributes to the quality of forest resource information.
Remote sensing produces more consistent information than terrain assessment
The quality of a traditional terrain assessment always depends on the assessor. In laser survey, the quality is in many respects more uniform.
In a terrain assessment, the mean error of the total volume is usually between 15 and 25 %. The accuracy of laser survey is the same or more accurate in mature and regeneration forests. In addition, in laser survey, the interpretation of trees is uniform and does not depend on different factors. The information on the total growing stock is the most accurate and the information on the main tree species is usually correct. With the development, tree species information has also improved. However, errors can occur in species composition in mixed stands, and especially when a tree species is scarce.
In laser survey, the accuracy requirement in growing and regenerating mature forests is that the total volume should be within 20 percent for eight out of ten compartments. This has been the case for a long time and with development the results have also been more certain.
In laser survey, separate quality criteria have been defined for the average length, average diameter, and basal area of the total growing stock. The average length should be +/- 2 m, the average diameter 3 cm, and the basal area 3 m² / hectare for eight compartments out of ten.
The information on the length of the trees is the most accurate, the diameter information is usually good, and the basal area is most often within the range given above. There is no actual quality criterion for the number of trunks in seedling stands, but for seedlings, the most relevant information is the need for tending.
The age of the tree stand is the most difficult indicator because laser survey is mainly based on the visible features of the tree stand and the age of stands of the same size can vary by tens of years. Often, however, the age of the stand is proportional to its size, so the information on the age of the stand is usually in the right direction. On the other hand, the importance of tree stand age in forestry has decreased.
In general, the aim is to keep the errors in the tree stand characteristics in such a range that they do not cause significant deviations from the timely proposals for measures.
In seedling stands and uneven forest compartments, the accuracy of remote sensing decreases
For resource reasons, forest resource information is no longer collected as a terrain assessment by compartments. Remote sensing is well suited for more mature forests, but it is less reliable the smaller the tree stand. Laser survey can also be performed with moderate accuracy in terms of tending needs in mature seedlings, but it is not suitable for small seedling stands at all. These sites need other sources of information, such as data on regeneration and management measures.
The number of errors in laser survey increases if the forest compartment is uneven, multi-storeyed, or otherwise deviates from the normal forest in the area. Assessing uneven compartments or small sections of tree species is also difficult in terrain. However, the most important forestry measure, which is taken in the forest, is usually determined by the prevailing tree stand in the forest compartment.
Quality of nature information
Comprehensive and up-to-date information on habitats of special importance protected under section 10 of the Forest Act is important for the Forest Act enforcement. The Forest Information Act on information managed by the Finnish Forest Centre requires that information on the Forest Act sites, as well as other information describing the forest, be updated regularly. The aim of the Finnish Forest Centre is to ensure that this material, which is important in law enforcement, is available as comprehensively as possible and that the material is up to date. We are constantly working to improve quality and coverage.
Challenges in describing habitats of special importance
The information concerning habitats of special importance referred to in section 10 of the Forest Act may contain inaccuracies, and that is, among other things, because the history of the sites’ management differs substantially from the normally managed commercial forest. The sites have long evolved as natural or semi-natural. Due to this, tree stands are sometimes so variable in size and age that it is difficult to accurately describe the stands, especially in lush habitat types. Habitat types are mainly defined based on vegetation.
The determination of vegetation and, on the other hand, also the assessment of the degree of naturalness of the site is based on visual assessment. Also, within each habitat type itself, there is an inherent variation between different sites. The characteristics of the sites differ to some extent due to, among other things, conditions related to the site and the climate.
The current spatial data set of the Finnish Forest Centre does not contain information on all the existing sites under section 10 of the Forest Act, because a large part of the sites has not yet been found. This should be considered when assessing the accuracy of information on habitats of special importance.
The quality of the information received by the Finnish Forest Centre is assessed by means of spatial data sets and, if necessary, an on-site inspection.
Forest and nature information is updated based on applications and notifications received in connection with the management of the Finnish Forest Centre’s administrative matters. In addition, the information may be updated based on other information submitted to the Finnish Forest Centre, if the information does not, according to the estimation of the Finnish Forest Centre, contain nonconformances, errors or misinterpretations.
The Finnish Forest Centre is not responsible for the accuracy of this information or information received from the authorities. However, the Finnish Forest Centre is responsible for the accuracy of the information to the extent that the accuracy of this information has been verified by a Finnish Forest Centre employee in connection with an on-site inspection.
Spatial data sets are primarily used to check the quality of nature information provided by third parties. The site is inspected in the terrain if the inspection cannot be performed reliably with the help of available spatial data or if section 10 of the Forest Act restricts the management of the site.
If the data of the site cannot be reliably checked using the available spatial data sets and the site is to be considered in forest use or the material affects forest use, the Finnish Forest Centre will ask the party that provided the material for more information about the site. If the quality of the material cannot be ascertained after the contact, the Finnish Forest Centre will set the status of the site as uncertain and, if necessary, will put it in the on-site inspection queue.