Climate Warming Will Reduce Boreal Forest Litterfall, but the Response Differs Among Plant Functional Types.

Area of Science:

• Ecology
• Forestry
• Climate Science

Background:

• Boreal forests are critical carbon sinks, with over two-thirds of carbon stored in soil and litter.
• Litterfall is essential for carbon and nutrient cycling in these ecosystems.
• Understanding litterfall dynamics across different plant functional types (deciduous, evergreen, mixed) and ages is limited.

Purpose of the Study:

• To analyze litterfall production dynamics in relation to stand age and temperature across boreal plant functional types.
• To project future boreal litterfall production trends under two CMIP6 climate scenarios (SSP2-4.5 and SSP5-8.5).

Main Methods:

• Synthesized boreal litterfall data from published studies.
• Applied generalized additive models to examine litterfall dynamics.
• Utilized CMIP6 climate scenarios for future projections.

Main Results:

• Mean litterfall production was 1959 kg ha⁻¹ year⁻¹, with deciduous forests producing the most.
• Litterfall production peaked at 60 years for evergreen and 150 years for mixed forests; no significant age trend in deciduous forests.
• A temperature threshold of 5°C stabilized litterfall in evergreen forests.
• Both climate scenarios predict widespread declines in litterfall by 2100, with SSP5-8.5 showing declines exceeding -20% in 70% of forests.

Conclusions:

• Plant functional type and stand age are critical factors for accurate litterfall production modeling.
• Future climate change is expected to significantly reduce boreal litterfall, impacting carbon and nutrient cycling.
• Findings enhance understanding of vegetation-climate interactions in boreal forest ecosystems.