Tree mortality from drought, insects, and their interactions in a changing climate.

Area of Science:

• Ecology
• Forestry
• Climate Science

Background:

• Climate change is predicted to increase tree mortality due to drought, heat stress, and insect outbreaks.
• Current ecosystem models often lack the capacity to accurately represent climate-induced tree mortality and biotic disturbances.
• Understanding these drivers is essential for predicting the future of forest ecosystems.

Purpose of the Study:

• To develop a framework for quantifying the relative contributions of drought stress and insect attack to tree mortality.
• To improve process-based ecosystem models by incorporating climate-driven mortality factors.
• To analyze cross-biome patterns of insect-driven tree mortality and compare temperate and tropical regions.

Main Methods:

• Utilized data sets from the western USA and related studies.
• Developed a framework to identify mechanisms of tree mortality caused by bark beetles and defoliators.
• Reviewed existing evidence on insect outbreak prevalence across different biomes.

Main Results:

• Identified key mechanisms driving tree mortality from bark beetle and defoliator guilds.
• Highlighted the interaction between drought stress and insect attacks in causing tree mortality.
• Provided insights into regional differences in insect outbreak prevalence.

Conclusions:

• A framework is presented to better model climate-driven tree mortality, incorporating insect interactions.
• Accurate projections of forest ecosystem responses require a multitrophic approach considering tree physiology, insect populations, and tree-insect interactions.
• Addressing challenges in modeling requires integrated tools and further research into tree-insect dynamics under climate change.