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Automated tree detection and crown delineation using airborne laser scanner data in heterogeneous east-central europe forest with different species mix

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Journal of Forestry Research 2017年第5期28卷 1049-1059页

作者： Róbert Smreek Ivan Sakov Zuzana Michnová Ján Tuek Department of Forest Management and Geodesy Technical University in Zvolen Department of Forest Policy Economics and Forest ManagementNational Forest Centre-Forest Research Institute Zvolen

Identifying tree locations is a basic step in the derivation of other tree parameters using remote sensing techniques, particularly when using airborne laser scanning. There are several techniques for identifying tree positions. In this paper, we present a raster-based method for determining tree position and delineating crown coverage. We collected data from nine research plots that supported different mixes of species. We applied a raster-based method to raster layers with six different spatial resolutions and used terrestrial measurement data as reference data. Tree identification at a spatial resolution of 1.5?m was demonstrated to be the most accurate, with an average identification ratio (IR) of 95% and average detection ratio of 68% being observed. At a higher spatial resolution of 0.5?m, IR was overestimated by more than 600%. At a lower spatial resolution of 3?m, IR was underestimated at less than 44% of terrestrial measurements. The inventory process was timed to enable evaluation of the time efficiency of automatic methods.

关键词： Airborne laser scanning east-central europe Individual tree Mixed forest Tree crown delineation

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Long-term changes and periodicity of ice phenomena in the high mountain Lake Morskie Oko(Tatra Mountains,Western Carpathians)

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Journal of Mountain Science 2022年第11期19卷 3063-3075页

作者： POCIASK-KARTECZKA Joanna NIECKARZ Zenon CHOIŃSKI Adam Institute of Geography and Spatial Management Jagiellonian UniversityKraków 30387Poland Marian Smoluchowski Institute of Physics Jagiellonian UniversityKraków 30348Poland Institute of Physical Geography and Environmental Planning Adam Mickiewicz University in PoznańPoznań61680Poland

High montain lakes are regarded as sensitive indicators of environmental changes in local and global scales.In recent years,climate change has considerablely influenced the timing of ice phenomena in these lakes.The objective of the paper is an investigation of long-term changes and periodicity of ice phenomena in high mountain Lake Morskie Oko(1392.8 m a.s.l.)located in the Tatra Mts.in the period 1971-2020.The study employed the Lomb-Scargle periodogram,linear regression modelling for temporal trends,correlation analysis,parameters of variability,and flashiness index.Periodicity of the duration of ice phenomena(~5.4 y)and ice cover on the lake(~13.5 y)was observed,although both are statistically insignificant.Ice cover duration has been interrupted several times by winter thaws after 1996 whereas no such events had been reported earlier.The trend towards a delayed appearance of ice phenomena reaches 4.0 d·decade^(-1)(p<0.001).The observed trend towards an earlier ice phenomena disappearance reaches 5.1 d·decade^(-1)(p<0.001).It results in a decline of the number of days with ice phenomena on Lake Morskie Oko at a rate of 9.0 d·decade^(-1)(p<0.001).The duration of ice cover on Lake Morskie Oko has been decreasing at a rate of 10.4 d·decade^(-1).It is attributed to later freezeup(3.9 d·decade^(-1),p<0.001)and earlier ice break-up(5.6 d·decade^(-1),p<0.001).An increasing trend of average annual air temperature(0.4°C·decade^(-1),p<0.001)in the period 1971-2020 is observed.A statistically significant correlation is recorded between ice phenomena and ice cover(beginning,end,duration),average annual air temperature,average air temperature of three summer months(June,July,August),and average air temperature of the six months period from June to November.Higher air temperature induces growing heat resources accumulated in the lake water in the summer and autumn seasons,potentially causing later initiation of ice phenomena in the lake.There is no statistically significant relationship between maximum ice thickness and an

关键词： Ice phenomena Lakes High mountains Climate warming east-central europe

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