Limiting Resources Define the Global Pattern of Soil Microbial Carbon Use Efficiency

Area of Science:

• Soil science
• Microbial ecology
• Biogeochemistry

Background:

• Microbial carbon use efficiency (CUE) is crucial for soil carbon sequestration.
• Factors controlling CUE are poorly understood, creating uncertainty in soil carbon retention predictions.
• Global change impacts on soil carbon require a clear understanding of CUE.

Purpose of the Study:

• To investigate global patterns of microbial CUE in surface soils.
• To examine the relationship between CUE and environmental factors like temperature, precipitation, and nutrient availability.
• To understand how climate zones influence CUE and soil carbon retention.

Main Methods:

• Stoichiometric modeling was used to estimate CUE.
• Data from surface soils across natural ecosystems globally were analyzed.
• Associations between CUE and environmental variables were examined within climate zones.

Main Results:

• CUE is primarily determined by the most limiting resource (temperature, water, plant C, or nutrients).
• Higher CUE was observed in arid and cold zones, linked to resource limitations.
• Lower CUE was found in tropical and temperate zones, often due to nutrient limitations (N or P).
• CUE increased with latitude due to contrasting resource limitations across climate zones.

Conclusions:

• Resource limitations are key drivers of microbial CUE.
• Global change may lead to reduced soil carbon retention in high-latitude, arid/cold regions due to decreased CUE with warming.
• Oligotrophic soils in low latitudes might increase carbon retention with nutrient enrichment.
• Soil carbon retention responses to global change are asymmetric across latitudes.