Canopy leaf temperatures of selected tree species growing in the forest and outside the forest using aerial thermal infrared (3.6-4.9 µm) data
Studies conducted in recent years have demonstrated high application potential of thermal remote sensing data in environmental analyses. However, the application potential of airborne thermal data has not been well recognized yet due to, among other things, the novelty of the sensors. This study was conducted on five selected tree species: Alnus glutinosa, Pinus sylvestris, Quercus petraea, Quercus rubra and Robinia pseudoacacia. The study area was 102.33 km2 in the National Park of Wielkopolska (Poland). Thermal data were acquired on June 9, 2019, between 8:10 and 14:00 (CET). The temperature was recorded by the ImageIR 9400 sensor with a spectral range of 3.6-4.9 μm. The main goal of our studies was to determine the variability of tree canopy temperatures using a sensor with a new spectral range. The findings were as follows: 1) Trees growing in the forest are on average 0.4-0.7oC cooler than trees outside the forest; 2) The results indicate that the canopy leaf temperatures of species under study differ statistically significantly irrespective of data acquisition time. The studies showed that the biggest variation between species in the canopy leaf temperature occurs at about noon (12:00-13:00); 3) A thermal spectral range of 3.6-4.9 μm registers the canopy leaf temperature of tree species with a high accuracy, which supports its usage in remote sensing vegetation studies.