Determination of differences in temperature regimes on healthy and bark-beetle colonised spruce trees using a handheld thermal camera

Abstract

Biogeosciences and ForestryBiogeosciences and Forestry Determination of differences in temperature regimes on healthy and bark-beetle colonised spruce trees using a handheld thermal camera Andrej Majdák (1) , Rastislav Jakuš (1-2) , Miroslav Blaženec (1) In this study, we compared the daily temperature regimes of healthy uninfected trees in the interior of a forest stand and at the fresh forest edge with infested trees at the forest edge in an area affected by a bark beetle outbreak. We estimated the potential of a handheld thermal camera for early identification of bark-beetle infested trees. We show that infested trees have significantly higher trunk temperatures than uninfested trees, which is more visible on the shine side of the trunk, and we report the differences in temperature between the shine and shadow sides. The differences are more noticeable on a warm, bright, and sunny day than on cold and cloudy day. The different intensity of solar radiation does not affect the distinction between infested and uninfested trees. The handheld thermal camera shows potential for identifying bark-beetle infested trees by scanning tree trunks on bright sunny days.

Physiological and biochemical indicators in Norway spruces freshly infested by Ips typographus: potential for early detection methods

“…However, the average difference compared to the intact trees was only about 0.4 • C, which is below the sensitivity threshold of the sensors. A study by Majdák et al (2021) reported using an infrared-based thermo-camera to distinguish infested trees on forest edges. They found a significant difference in bark surface temperature (reaching tens of • C) only on the sun-exposed side of infested trees on days when air temperature reached 34 • C and bark surface temperature was nearly 60 • C. The temperature difference on the shaded side was lower, and on colder days (maximum air temperature of 24 • C), it was not significant, which corresponds with our findings.…”

“…A previous study (Majdák et al, 2021) reported a measurable increase in bark surface temperature following bark beetle infestation in sun-exposed trees on the forest edge. These trees were weakened by infestation and could not keep the optimal temperature.…”

GreenScan: Toward Large-Scale Terrestrial Monitoring the Health of Urban Trees Using Mobile Sensing

“…Imaging-based methods involve the use of optical sensors such as thermal imaging sensors, HMI (hyperspectral or multispectral imaging) sensors or LiDAR (Light Detection and Ranging). Thermal imaging is based on IR (InfraRed) radiation emitted from materials and it is mainly used to (i) measure cavities and physical damages in the living wood [29], [30], (ii) detect infections caused by insects and bacteria [31], [32], and (iii) calculate water stress levels by measuring the temperature of the leaves in the canopy [14]. On the other hand, HMI sensors capture various bands in the electromagnetic spectrum, usually near-infrared and parts of the visible spectrum.…”

TreeNet–The Biological Drought and Growth Indicator Network

“…However, note that the temperature expansion coefficient is usually determined for dry wood (5−15% moisture content) with no such coefficients existing for moist, live tree stems, including bark. As such, a 10 • C change in air temperature results in a smaller temperature change in the stem because the sap transported in the wood cools the stem during the day (Majdak et al, 2021). Furthermore, any size changes due to temperature affecting the wood deeper in the stem than the anchoring of the dendrometer takes place (about 5−10 cm in the case of the dendrometers used in TreeNet) is likely irrelevant as the dendrometer reading is not affected.…”