Ectomycorrhizal colonization slows root decomposition: the post-mortem fungal legacy

Area of Science:

• Soil Science
• Mycology
• Plant Ecology

Background:

• Plant roots are a significant source of soil carbon.
• Ectomycorrhizal (EM) fungi form symbiotic relationships with plants, influencing nutrient cycling.
• The decomposition fate of EM-colonized roots and its impact on soil carbon remain poorly understood.

Purpose of the Study:

• To investigate the decomposition rates of ectomycorrhizal (EM) versus non-mycorrhizal plant roots.
• To determine the role of live EM fungi versus their decomposed litter in root decomposition.
• To assess the potential of EM fungi in promoting soil carbon accumulation.

Main Methods:

• Comparing carbon loss from EM and non-EM roots over two years in a Pinus edulis woodland.
• Experimentally excluding live mycorrhizal hyphae from root litter to differentiate between live and litter-mediated effects.
• Analyzing nitrogen concentrations in decomposing roots.

Main Results:

• EM roots lost significantly less carbon (one-third) than non-mycorrhizal roots over two years, despite higher nitrogen content.
• The decomposition-inhibiting effect was primarily attributed to the litter of EM fungi, not live hyphae.
• Live EM hyphae influenced nitrogen dynamics but had less impact on decomposition rates compared to litter effects.

Conclusions:

• Plant allocation to EM fungi can increase soil carbon accumulation through slower root decomposition.
• EM root litter contributes to stable soil organic matter formation, a novel pathway for soil carbon sequestration.
• Understanding EM fungal roles is crucial for predicting soil carbon dynamics and developing effective soil management strategies.