Drought-induced increase in tree mortality and corresponding decrease in the carbon sink capacity of Canada's boreal...

Area of Science:

• Forest Ecology
• Climate Change Science
• Carbon Cycle Research

Background:

• Canada's boreal forests are vital to the global carbon budget, covering 30% of the world's boreal area.
• Quantitative data on drought-induced tree mortality and its impact on carbon dynamics in these forests are limited.
• Understanding these changes is crucial for predicting future climate feedback loops.

Purpose of the Study:

• To quantify spatiotemporal changes in drought-induced tree mortality in Canada's boreal forests from 1970 to 2020.
• To estimate the impact of increased tree mortality on biomass carbon dynamics.
• To project future carbon sink capacity under changing drought conditions.

Main Methods:

• Development of spatiotemporally explicit estimates of tree mortality.
• Analysis of biomass carbon sink capacity changes.
• Utilizing data spanning 1970-2020 to identify trends and acceleration points.

Main Results:

• Average annual tree mortality rate is approximately 2.7%.
• Over 43% of Canada's boreal forests show increasing tree mortality trends, accelerating since 2002, primarily in the west.
• Significant biomass carbon losses are occurring at ~1.51 MgC ha⁻¹ year⁻¹, totaling ~0.46 PgC year⁻¹.

Conclusions:

• Increased tree mortality is significantly reducing the carbon sink capacity of Canada's boreal forests.
• Projected increases in drought will further diminish this capacity.
• These changes may lead to a substantial positive climate feedback effect.