Microbial necromass contribution to soil carbon storage via community assembly processes

Area of Science:

• Soil Science
• Microbiology
• Ecology

Background:

• Soil organic matter (SOM) is crucial for climate change mitigation and agricultural productivity.
• Microbial necromass significantly contributes to soil organic carbon (SOC) storage.
• The dynamics of microbial necromass in SOC remain poorly understood, particularly the balance between microbial life and death.

Purpose of the Study:

• To investigate the impact of varying maize stover mulching rates on microbial necromass contribution to SOC.
• To understand how soil microbial community assembly influences the fate of microbial necromass.
• To elucidate the biological mechanisms behind SOC storage related to microbial necromass.

Main Methods:

• Coupling soil microbial community analysis (using iCAMP) with microbial necromass quantification (via amino sugars).
• Implementing a long-term no-till (NT) field experiment with 0%, 33%, 67%, and 100% maize stover mulching over 8 years.
• Analyzing bacterial and fungal community responses to different mulching treatments.

Main Results:

• 100% maize stover mulching (NT100) resulted in significantly lower amino sugar concentrations (a proxy for microbial necromass) compared to other treatments.
• Bacterial communities showed increased phylogenetic diversity, while fungal communities exhibited enhanced taxonomic richness under maize stover mulching.
• Soil bacterial assembly influenced SOC contribution through deterministic processes, while fungal taxonomic richness, driven by dispersal limitation in saprotrophic guilds, impacted SOC accumulation.

Conclusions:

• Microbial community assembly, especially fungal richness and specific bacterial groups like Chitinophagaceae, plays a key role in regulating microbial necromass contribution to SOC.
• High levels of maize stover mulching may decrease microbial necromass in SOC due to shifts in microbial community structure and function.
• Findings provide insights into biological mechanisms of SOC storage, with implications for sustainable agriculture and climate change mitigation.