Climate change impact on physiological and chemical responses of mature Norway spruce (Picea abies) in relation to bark beetle attack susceptibility

Ing. Barbora Stříbrská

Doctoral thesis

Abstract:

Eurasian Spruce Bark Beetle (Ips typographus, L. 1758 (Coleoptera: Scolytinae)) outbreaks have a severe impact on Norway spruce forests in Central Europe. Forest damage is exacerbated by abiotic disturbances, logging, and forest fragmentation, increasing the vulnerability of spruce forest stands. This thesis explores how Norway spruce trees react to sudden exposure on a newly formed forest edge and on infestation by bark beetles, examining physiology, defence, and parameters related to bark beetle acceptance and attraction. The goal is to provide ecological insights into these processes and propose innovative methods for managing bark beetle infestations. The first study investigates the immediate effects of forest edge establishment on critical parameters, including air and bark temperatures, soil water potential, sap flow, resin flow, bark defence compounds, and olfactometric cues for bark beetles. Observations in newly cut forest edges during spring reveal elevated bark temperatures and volatile organic compound (VOC) concentrations. Despite similar monoterpene levels in the bark, VOC concentrations were highest in May and June, coinciding with increased Ips typographus mobility, indicating that microclimatic conditions and olfactory signals contribute to beetle swarming. The study demonstrates that fresh forest edges are not disproportionately susceptible shortly after establishment, emphasizing the role of microclimatic conditions, induced tree defence and olfactory cues in spruce bark beetle infestation patterns. Furthermore, two publications focus on the physiological and defence responses of Norway spruce to bark beetle infestation. Besides studying these alterations, these publications also propose novel methods for early detection of Ips typographus infestations. Monitoring infested and non-infested Norway spruce trees reveals post-attack reductions in sap flow, terminated tree stem increment, increased bark temperature, and a surge in monoterpene emissions. Promising early detection approaches encompass the surveillance of tree bark temperature during specific meteorological conditions, analysis of monoterpene emissions, and the observation of elevated captures in passive traps. The analytical chemistry part of the study focuses on detecting volatile organic compounds, especially α-pinene, emitted by infested trees. Lab trials were performed to optimize α-pinene detection by dynamic absorption and solid-phase microextraction (SPME), revealing variable abundance in forest trials. Three-dimensional cloud mapping of α-pinene distribution suggests the potential for large-scale bark beetle detection, paving the way for alternative pest management methods using scanning technologies.

Keywords

α-pinene, early detection, forest edge, Ips typographus, Picea abies, sun irradiation, tree susceptibility, VOCs

Language used: English

Date on which the thesis was submitted / produced: 21. 1. 2024

Thesis defence

• Supervisor: Ing. Anna Jirošová, Ph.D.
• Reader: Klára Urbanová, Ph.D., doc. Ing., Jonathan Gershenzon, externi, Martin Schebeck, externi

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Doctoral programme:
Global Change Forestry