During my internship at European Forest Institute in Finland I had a chance to become familiar with Finnish method of forest stands volume estimation. The Finnish way of forest inventory was quite innovative in relation to the method which have been used in Poland, so I thought that it could be nice subject for the master thesis.
The development of the Finnish Multi-Source National Forest Inventory began in 1989, and the first effective results were computed in 1990. The main goal of discussed method elaboration was the need to obtain forest source information for large areas with maintaining low work effort and overall expenditures. So far Finnish Forest Research Institute has carried out 9 revisions of the national forest inventory. The method conducted by the Finnish Forest Research Institute has used satellite images, digital elevation model and digital map data, in addition to field measurements. Nevertheless, the essential data for MS-NFI are derived from ground plots and satellite images, whereas digital map data as well as digital elevation model improve significantly accuracy of the prediction. Generally method can be employed in a straightforward way in different forest conditions, and with different remote sensing materials.
My area of interest was Stolowe Mountains National Park (also known as the Table Mountains), which is located in Poland near the border of the Czech Republic, between 50°24’30’’ and 50°30’15’’ north latitude, and 16°16’15’’ and 16°26’24’’ east longitude. The highest elevation is situated in western part of the study area, and is equal to 919 meters-a.s.l., whereas the lowest elevation is located in northeastern part, and is equal to 393 meters-a.s.l. The climate of the Stołowe Mountains National Park belongs to mountain climate. Precipitation increases with the altitude, exceeding 660 mm in the lowest part of the park and 1000 mm in the highest part. Snow remains in the highest part of the park over 120 days a year, whereas vegetation period persists around 195 days a year. National Park was established in 1993, and it covers 6327,88 ha, where forest stands occupy 5803,24 ha, and non-forest areas cover 524,64 ha. Spruce is the dominant species which occupies 78% of the total area. Second species in terms of quantity occurrence in the study area concerns beech and is equal to 12%. The remaining 10% is occupied by other mainly deciduous species. Following map describes percentage quantity of the dominant species and their spatial distribution respectively.
In order to obtain reference data the whole area of the Stołowe Mountain National Park has been covered uniformly by ground plots. The size of single field sample plot was equal to 500 m2, whereas the spacing between individual plots were 400 x 400 m.
Originally, 395 ground plots have been established, however, for the computation purposes, 62 plots have been discarded, because some of them were not located directly in the stand but, for instance, on the meadows or roads. Height measurements were estimated by using Suunto devices, whereas DBH measurements were done by using caliper. Inventory teams measured DBH between intervals 8–12 cm for each tree, which was located in the core zone 50 m2 of the sample plot, whilst in the whole plot of 500 m2, the measurements were taken for each trees that exceeded 12 cm of the DBH. After collecting the necessary data, timber volume in cubic meter per hectare was calculated for each plot. Following map shows field sample plots distribution in the study area.
The satellite image has been downloaded from USGS Global Visualization Viewer, which provides free satellite images for the almost whole Earth. The image that was derived from Landsat 7 satellite consisted of seven spectral bands with a spatial resolution equal to 30 m × 30 m for each pixel. Following map describes satellite image.
Digital map data in raster format with spatial resolution of 30 m × 30 m have been used in order to reduce the estimate errors. In order to obtain the above-mentioned aim, the examined area has been divided into forestry land and non-forestry land, such as arable land, urban areas, build-up areas and roads. Following map shows digital map in raster format.
Digital Elevation Model has been used to remove the variation of the spectral values that were caused by the changes in the slope and aspect of the terrain normal – map below.
In order to perform calculations, it is necessary to install R Statistical Software. Digital map data were created from vector data and rasterised to the pixel size of 30 m × 30 m by using ArcGIS Software. Digital Elevation Model also had to be aggregated to the same pixel level of 30 m × 30 m, because all raster data that have been pulled into calculations must have the same pixel size. Landsat satellite image has been processed by using ERDAS IMAGINE 2014 Software.
Total predicted timber volume in the study area reached 2,132,997 m3, which means that average timber volume on the forested area was equal to 366.6 m3/ha. Maximum predicted timber volume reached 1149.5 m3/ha, whereas minimum predicted timber volume was equal to 0.9 m3/ha.
Research results and their comparison with other research outputs allowed to state that k-NN technique as well as genetic algorithm used in MS-NFI are very promising and powerful tools with regard to the timber volume estimation. It must be pointed out that given timber volume results are similar to previous LIDAR measurements, which were done in the same study area and in similar time period.
Following map have been generated from R software, and shows timber volume estimation in the entire area.
More interested in the topic can refer to the following article, where I describe in a more detailed way discussed method: Finnish Multi Source National Forest Inventory in Stołowe Mountains National Park. Folia Forestalia Polonica, ser. A, 58 (1): 3-13.
Author of the post:
Przemko Pachana – forester, graduate of Forestry from the Warsaw University of Life Sciences and Forest Information Technology from the Eberswalde University for Sustainable Development.
Professional experience gained i.a. at European Forest Institute in Finland and Polish State Forests.
Currently has been working in Germany in a company which mainly deals with forest management plans, and forestry software and mobile applications development.
Main photo: Szczeliniec Wielki – the highest peak (919 m) at Table Mountains, in the Table Mountains National Park. Szczeliniec is one of the biggest tourist attractions of the Sudetes, the landscape reserve and viewing terraces with panoramic views of the Sudetes. It is worth to mention that whole range of Table Mountains is formed of sandstone and, as the only one in Poland, presents plated structure with sheer mountain ledges. Autor of the photo: Rafal Chudy