Detection of susceptible Norway spruce to bark beetle attack using PlanetScope multispectral imagery

Abstract

Climate change-related acute or long-term drought stress can weaken forest ecosystems and result in widespread bark beetle infestations. Eurasian spruce bark beetle (Ips typographus L.) infestations have been occurring in Norway spruce [Picea abies (L.) Karst.]-dominated forests in central Europe including the Czechia. These infestations appear regularly, especially in homogeneous spruce stands, and the impact varies with the climate-induced water stress conditions. The removal of infected trees before the beetles leave the bark is an important step in forest pest management. Early identification of susceptible trees to infestations is also very important but quite challenging since stressed tree-tops show no sign of discolouration in the visible spectrum. We investigated if individual spectral bandwidths or developed spectral vegetation indices (SVIs), can be used to differentiate non-attacked trees, assumed to be healthy, from trees susceptible to attacks in the later stages of a growing season. And, how the temporal-scale patterns of individual bands and developed SVIs of susceptible trees to attacks, driven by changes in spectral characteristics of trees, behave differently than those patterns observed for healthy trees. The multispectral imagery from the PlanetScope satellite coupled with field data were used to statistically test the competency of the individual band and/or developed SVIs to differentiate two designated classes of healthy and susceptible trees. We found significant differences between SVIs of the susceptible and healthy spruce forests using the Enhanced Vegetation Index (EVI) and Visible Atmospherically Resistant Index (VARI). The accuracy for both indices ranged from 0.7 to 0.78; the highest among all examined indices. The results indicated that the spectral differences between the healthy and susceptible trees were present at the beginning of the growing season before the attacks. The existing spectral differences, likely caused by water-stress stimuli such as droughts, may be a key to detecting forests susceptible to early infestations. Our introduced methodology can also be applied in future research, using new generations of the PlanetScope imagery, to assess forests susceptibility to bark beetle infestations early in the growing season.

Sap flow as a function of variables within nested scales: ordinary least squares vs. spatial regression models

“…Distances among subplots within a plot ranged 40-250 m. The six established plots, within a 100 m elevation range, were designed under EXTEMIT-K project. The project was proposed to conduct research experiments to deliver science-based approaches for dealing with the environmental challenges of protecting Norway spruce forests in the Czech Republic (Trubin et al 2023). Bark beetle infestations and periodic drought effects on trees and beetle infestation dynamics were the main challenges in this project (Trubin et al 2023).…”

Effect of Diurnal Solar Radiation Regime and Tree Density on Sap Flow of Norway Spruce (Picea Abies [L.] Karst.) in Fragmented Stands

“…The study site contained six plots of mature (90-100-year-old) Norway spruce stands situated in a commixture of oak-beech vegetation zone. The vegetation of this area had a predominance of conifer forest with an admixture of r and beech, but at the time of study spruce (50%) and pine (16%) were the dominant species (Trubin et al, 2023). The forest stands have been extensively managed through classical silvicultural practices, mainly thinning.…”

An Optimized and Cost-Effective RNA Extraction Method for Secondary Metabolite-Enriched Tissues of Norway Spruce (Picea abies)

“…Ongoing climate change has had a negative impact on the Norway spruce population in the forest [1]. The rise in spruce mortality over the past few decades can be attributed to a combination of biotic factors, such as bark beetle (Ips typographus) outbreaks and fungal pathogens, and abiotic factors, including drought and windthrows, or a combination of both [2][3][4]. In particular, bark beetle outbreaks are often triggered by environmental factors, such as droughts and increased temperatures, resulting in compromised tree defense.…”