## 3 Results
### a-Pinene Spatial Distribution around Norway Spruce Infested by Ips typographies for Two Weeks  
The conditions in the first forest spatial VOC measurement conducted on 30 June 2022 on two-week naturally infested trees were an average temperature of 25.1 \({}^{\circ}\)C, average humidity of 72.6%, wind speed of 5 km/h, wind direction from the SE, and sunshine. The abundance of a-pinene emitted from the naturally infested tree was upregulated at a 5 cm distance from the stem. This upregulation was detected by both collection methods, with a significant increase observed using SPME (\(p\) = 0.036), where 5 cm and 100 cm distances significantly differed (\(p\) = 0.036 post hoc) (Figure 6a) and a non-significant increase was observed using sorption to cartridges (\(p\) = 0.0585). A trend of a decreasing \(\alpha\)-pinene concentration at a 900 cm distance from the infested tree was observed in the collection involving cartridges (Figure 6d), but not in the collection using SPME (Figure 6a). In the vertical direction, a weak, non-significant trend was observed in the accumulation of \(\alpha\)-pinene in the bottom level of the stem at 130 cm above the ground, decreasing with altitude up to 400 cm above the ground. This trend was consistent across both collection methods (Figure 6b,e). Regarding cardinal orientation, there was no significant accumulation of \(\alpha\)-pinene on any of the measured sides. However, considering the high variability of the data, there was a trend of increased \(\alpha\)-pinene abundance on the south side of the infested stem, as observed with both SPME fiber and cartridge collection methods (Figure 6c,f). A 3D depiction of the \(\alpha\)-pinene collection using SPME fiber on 30 June 2022 is shown in Figure 7. Increased color saturation in the visualization corresponds to higher accumulated  
Figure 6: First field detection of \(\alpha\)-pinene distribution around _Ips typographies_-infested spruce (30 June 2022). (**a**) Abundance of \(\alpha\)-pinene collected by SPME in different distances from stem (5 cm; 100 cm; 900 cm); (**b**) abundance of \(\alpha\)-pinene collected by SPME at different height levels from ground (130 cm; 260 cm; 400 cm); (**c**) abundance of \(\alpha\)-pinene collected by SPME in cardinal directions (§—south; N—north; E—east; W—west); (**d**) abundance of \(\alpha\)-pinene collected by HayeSep-Q® cartridges in different distances from stem (5 cm; 100 cm; 900 cm); (**e**) abundance of \(\alpha\)-pinene collected by HayeSep-Q® cartridges at different height levels from ground (130 cm; 260 cm); (**f**) abundance of \(\alpha\)-pinene collected by HayeSep-Q® cartridges in cardinal directions (§—south; N—north; E—east; W—west). Small red squares—Means; green boxes—Means \(\pm\) SE; Whiskers—Means \(\pm\)1.96°SE. Lowercase letters above columns indicate significant differences between different distance different height level, and different orientation. The \(p\)-values result from Kruskal–Wallis test. (\(n\) = 27 SPME samples) (cartridges \(n\) = 12). \(\alpha\)-pinene levels. The accumulation aligns with Figure 6, indicating elevated concentrations at the first level (130 cm). In terms of distance, there is a notable increase at 5 cm from the stem. Beyond 900 cm, there is considerable variation in \(\alpha\)-pinene amounts, making it difficult to observe a clear trend. Regarding the orientation, slightly higher concentrations are observed on the south and east sides, though are not significantly dominant. The conditions for the second VOC measurement in the forest open space around a naturally infested tree, conducted on 24 August 2022, differed from the first collection in terms of location and environmental factors (average temperature of 20.7 \({}^{\circ}\)C, average humidity of 78.8%, wind speed of 3 km/h, wind direction from S, and sunshine).