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The influence of number and size of sample plots on modelling growing stock volume based on Airborne Laser Scanning

Stereńczak K., Lisańczuk M., Parkitna K., Mitelsztedt K., Mroczek P., Miścicki S.

Drewno : prace naukowe, doniesienia, komunikaty

2018

vol. 61, nr 201

5--22

Current forest growing stock inventory methods used in Poland are based on statistical methods using field measurements of trees on circular sample plots. Such measurements are carried out with traditional equipment, i.e. callipers and range finders. Nowadays, remote sensing based inventory techniques are becoming more popular and have already been applied in North America and some Scandinavian countries. Remote sensing based forest inventories require a certain amount of ground sample plots, which serve either as reference data used for model calibration and/or as a validation dataset for the assessment of the accuracy of modelled variables. Using a set of 900 ground sample plots and Airborne Laser Scanner (ALS) from the Milicz forest district, a statistical model for the estimation of plot growing stock volume was developed. Next, the developed model was once again fitted to different variants of sample plot size and number of sample plots. Each variant was selected from a full 900 sample plot set. The selection started from 800, 700, 600, …, down to 25 plots, respectively, and was carried out in proportion to the dominant tree age range. To account for the area effect, each plot number variant was similarly tested with various sample plot areas, i.e. 500, 400, …, 100 m2. Sampling in each variant was repeated in order to take into account the effect of a single selection. The results showed a strong relationship between obtained modelling errors and the size and number of used sample plots. It has been demonstrated that the number of sample plots has no influence on the accuracy of GSV estimation above about 300-400 sample plots (about 500 sample plots for bias), whereas sample plot size has a visible impact on estimation accuracy, which reduces with decreasing sample plot size, regardless of the number of sample plots. If it is about precision, results showed that the influence of a single selection to be relevant only below 300-400 plots (about 500 for bias) and the same trend can be observed in each sample plot size variant. The results showed it is possible to strongly reduce the number of ground sample plots (minimum 300- 400), while still maintaining decent accuracy and precision levels, at least in similarly investigated forest conditions.

Determination of the spatial structure of vegetation on the repository of the mine "Fryderyk" in Tarnowskie Góry, based on airborne laser scanning from the ISOK project and digital orthophotomaps

Szostak M., Wężyk P., Pająk M., Hawryło P., Lisańczuk M.

Geodesy and Cartography

2015

Vol. 64, no. 1

87--99

The purpose of this study was to determine the spatial structure of vegetation on the repository of the mine “Fryderyk” in Tarnowskie Góry. Tested area was located in the Upper Silesian Industrial Region (a large industrial region in Poland). It was a unique refuge habitat – Natura2000; PLH240008. The main aspect of this elaboration was to investigate the possible use of geotechniques and generally available geodata for mapping LULC changes and determining the spatial structure of vegetation. The presented study focuses on the analysis of a spatial structure of vegetation in the research area. This exploration was based on aerial images and orthophotomaps from 1947, 1998, 2003, 2009, 2011 and airborne laser scanning data (2011, ISOK project). Forest succession changes which occurred between 1947 and 2011 were analysed. The selected features of vegetation overgrowing spoil heap “Fryderyk” was determined. The results demonstrated a gradual succession of greenery on soil heap. In 1947, 84% of this area was covered by low vegetation. Tree expansion was proceeding in the westerly and northwest direction. In 2011 this canopy layer covered almost 50% of the research area. Parameters such as height of vegetation, crowns length and cover density were calculated by an airborne laser scanning data. These analyses indicated significant diversity in vertical and horizontal structures of vegetation. The study presents some capacities to use airborne laser scanning for an impartial evaluation of the structure of vegetation.

Celem badań była ocena struktury przestrzennej roślinności porastającej zwałowisko odpadów kopalni ”Fryderyk” w Tarnowskich Górach, położone na północnym skraju Górnośląskiego Okręgu Przemysłowego. Teren, na którym znajduje się zwałowisko należy do sieci Natura 2000 (PLH 240008). Głównym aspektem poruszanym w opracowaniu było określenie możliwości wykorzystania ogólnie dostępnych geodanych dla opracowywania map pokrycia i użytkowania terenu zwałowiska oraz określenia struktury roślinności na tym obszarze. Analizowane materiały to zdjęcia i ortofotomapy lotnicze z lat: 1947, 1998, 2003, 2009, 2011 oraz dane z lotniczego skanowania laserowego (z projektu ISOK, 2011). Efektem opracowania było określenie charakterystyki przestrzennej roślinności na zwałowisku kopalni ”Fryderyk”. Analizy wykazały stopniową ekspansję roślinności na powierzchni hałdy. W 1947 roku 84% powierzchni terenu badań pokryta była przez roślinność niską a w roku 2011 roślinność wysoka zajmowała już około 50% obszaru zwałowiska. Analizy wykazały znaczne zróżnicowanie w poziomej i pionowej strukturze roślinności. W opracowaniu przedstawiono możliwości wykorzystania danych z lotniczego skanowania laserowego dla obiektywnej oceny struktury roślinności.