The spruce bark beetle (Ips Typographus) activity stands for a serious environmental and economic issue and presents a future challenge for the forest management not only in the Czech Republic, therefore early detection of bark beetle infestation is necessary to reduce losses. An overabundance of bark beetle affects not only the production of wood matter but the entire forest ecosystem, e.g. water supply or storage of carbon and nutrients, as well as reduce biodiversity. On that account, not only European temperate coniferous forests become importantly endangered ecosystems on the Earth. Finding out an accurate and early knowledge about infected trees by bark beetle outbreaks is challenging. Our study is localized in the non-intervention zone of the Krkonoše national park in the northern part of the Czech Republic. The aim is to evaluate possibilities of low-cost visible and modified near-infrared sensors mounted on UAV for early detection of infected single trees. The UAV-borne imagery was matched into mosaics and radiometrically calibrated into the surface reflectance; the reference data about the stage of bark beetle infection was obtained through a combination of field survey and orthomosaic visual interpretation. The differences of surface reflectance in blue, green, red, and near-infrared bands across dead, infected (in green and yellow stage), and healthy trees were graphically (spectral profile comparing) and statistically evaluated (linear regression). Achieved results confirm our assumptions that it is possible to use a low-cost (user-modified) UAV-based sensor for detection of an early stage of bark beetle infestation (p-value < 0.05); with increasing time after infection is distinguishability more provable (p-value < 0.05). However, for detection of the very early stage after bark beetle outbreak, the further research evaluating spectral characteristics of infected trees using a state of art multispectral and hyperspectral sensors is still needed.
The methodology was certified by the Ministry of Agriculture of the Czech Republic in March 2019. The methodology is available in the file below, however, only in the Czech language.