Data for the comparing microbial CUE in POM and MAOM in 25 natural ecosystem sites across China

Does microbial carbon use efficiency differ between particulate and mineral-associated soil organic matter? This is a key unsolved question to predict future changes in the carbon pool. Microbial carbon use efficiency is a key parameter in soil carbon models and is assumed to be similar for different soil functional pools with varied organic matter composition and nutrient availability, i.e., particulate organic matter (POM) and mineral-associated organic matter (MAOM). However, empirical studies comparing microbial carbon use efficiency of POM versus MAOM are largely lacking. It is essential to elucidate whether microbial carbon use efficiency differs between POM and MAOM to better inform soil carbon models and to better predict potential variations of soil organic carbon functional pools.

Here we isolated POM versus MAOM from 25 soils from natural forests and grasslands with divergent edaphic properties and compared their microbial carbon use efficiency using incubation with 18O-labeled water. Edaphic properties, organic matter composition, microbial community structures and nutrient availability were measured.

We do not find a consistent difference in microbial carbon use efficiency of the POM versus MAOM of diverse soils, but highlight potential contrasts in carbon use efficiency between soil pools under strong phosphorus limitation. Such inferences deserve attention under potentially increasing phosphorus limitation induced by nitrogen deposition. These findings provide empirical support for the use of similar microbial carbon use efficiency for POM and MAOM in soil models, which are central metrics and concepts in next-generation models closely related to predictions of carbon cycles under global changes. These results may help improve our understanding of ecological patterns and processes based on soil microbial physiology and different soil functional pools.