Tree defence and bark beetles in a drying world: carbon partitioning, functioning and modelling

Area of Science:

• Ecology
• Forest Science
• Climate Change Biology

Background:

• Drought exacerbates insect-induced tree mortality, impacting ecosystems and biogeochemical cycles.
• Physiological links between drought, tree defenses, and insect outbreaks remain unclear, limiting predictive accuracy.
• Current large-scale vegetation models inadequately represent insect-induced tree mortality.

Purpose of the Study:

• To propose an interdisciplinary research agenda to clarify the physiological linkages among drought, tree defenses, and insect outbreaks.
• To investigate how drought influences interactions between conifer trees and bark beetles.
• To improve predictions of forest disturbance under climate change by incorporating insect-tree dynamics.

Main Methods:

• Field manipulations and laboratory experiments to study tree physiological responses.
• Modeling of insect and vegetation dynamics, focusing on conifer-bark beetle interactions.
• Testing assumptions about carbon allocation trade-offs (growth vs. defense) and the role of secondary metabolites in tree defense.

Main Results:

• Drought-stressed trees may exhibit altered carbon allocation, potentially weakening defenses against insects.
• Secondary metabolites are confirmed as key components of conifer defense against bark beetles and associated microbes.
• Integrating conifer-bark beetle interactions into vegetation models enhances predictions of forest disturbance.

Conclusions:

• Addressing knowledge gaps in drought-insect-tree interactions is vital for accurate forest die-off prediction.
• The proposed research framework will improve large-scale vegetation models by accounting for insect-induced mortality.
• This work provides a foundation for understanding and mitigating forest vulnerability in a changing climate.