Root mixing effects on belowground decomposition depend on mycorrhizal type.

Area of Science:

• Ecology
• Forestry
• Soil Science

Background:

• Understanding species mixing effects on decomposition is crucial for soil carbon dynamics.
• Belowground root decomposition's role in soil carbon input is less understood than leaf litter decomposition.

Purpose of the Study:

• To experimentally assess how tree species mixing affects absorptive root decomposition.
• To identify factors influencing non-additive root decomposition in species mixtures.

Main Methods:

• Experimentally assessed root decomposition in 138 paired-species combinations from 57 tree species.
• Analyzed root chemistry (condensed tannins, nitrogen) and mycorrhizal type (ectomycorrhizal, arbuscular mycorrhizal).

Main Results:

• Significant non-additive mixing effects observed in 70% of root combinations, mostly faster decomposition.
• Non-additive effects were linked to the presence of ectomycorrhizal species and dissimilarities in root condensed tannins and nitrogen.
• Root mixing effects were three times stronger than previously documented for leaf litter.

Conclusions:

• Tree species mixing strongly influences belowground decomposition, particularly in forests with ectomycorrhizal species.
• Contrasting root chemistry in ectomycorrhizal species mixtures enhances decomposition rates.
• Root decomposition plays a vital role in tree species mixing effects on soil carbon and nutrient cycling.