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.

近年来，多项研究已证实热遥感数据在环境分析中的巨大应用潜力。然而，由于传感器的新颖性等因素，机载热数据的潜在应用尚未得到充分认识。本研究选取了五种树木物种：欧洲赤松（Alnus glutinosa）、欧洲赤松（Pinus sylvestris）、欧洲栎（Quercus petraea）、红枫（Quercus rubra）和刺槐（Robinia pseudoacacia）。研究区域位于波兰的大波兰国家公园（National Park of Wielkopolska），面积为102.33平方公里。热数据采集于2019年6月9日，时间介于8:10至14:00（中欧时间）。温度记录由ImageIR 9400传感器完成，其光谱范围为3.6-4.9 μm。本研究的主要目标是利用具有新光谱范围的传感器确定树冠温度的变异性。研究结果如下：1）森林内生长的树木平均比森林外的树木低0.4-0.7°C；2）结果表明，无论数据采集时间如何，研究物种的树冠叶片温度在统计学上存在显著差异。研究表明，树冠叶片温度在不同物种之间的最大差异出现在正午时分（12:00-13:00）；3）3.6-4.9 μm的热光谱范围能够以高精度登记树木物种的树冠叶片温度，这支持其在遥感植被研究中的应用。