Mycorrhizal fungi modify decomposition: a meta-analysis

Area of Science:

• Soil Ecology
• Mycology
• Biogeochemistry

Background:

• Ectomycorrhizal fungi (EMF) are proposed to reduce decomposition (Gadgil effect).
• Arbuscular mycorrhizal fungi (AMF) are proposed to enhance decomposition (priming effect).
• The global dominance of either the Gadgil or priming effect by mycorrhizal fungi remains unclear.

Purpose of the Study:

• To evaluate whether mycorrhizal fungi decrease or increase decomposition rates.
• To identify environmental conditions mediating the effects of mycorrhizal fungi on decomposition.
• To determine the predominant effect of mycorrhizal fungi on decomposition globally.

Main Methods:

• Synthesized decomposition data from 43 studies (97 trials) with controlled mycorrhizal fungal access.
• Analyzed effects across field and laboratory settings.
• Investigated the influence of substrate C:N ratio and absolute latitude on decomposition.

Main Results:

• Mycorrhizal fungi promoted decomposition by 6.7% overall, indicating a dominant priming effect.
• Substrate C:N ratio and absolute latitude significantly mediated this effect.
• Mycorrhizal fungi increased decomposition at low substrate C:N and low absolute latitude; no effect at high values.

Conclusions:

• Mycorrhizal fungi generally enhance soil decomposition, challenging the universality of the Gadgil effect.
• The priming effect predominates globally, influenced by substrate C:N ratio and latitude.
• Mycorrhizal fungi may negatively impact soil carbon storage by promoting decomposition.