In this new post, Professor Xiaojuan Feng from the Institute of Botany, Chinese Academy of Sciences presents her work ‘Does microbial carbon use efficiency differ between particulate and mineral-associated organic matter?’ She compares the microbial carbon use efficiency (CUE) in particulate organic matter (POM) and mineral-associated organic matter (MAOM), which represents different soil functional pools with varied organic matter composition and nutrient availability.
A Chinese translation of this blog post is available here!
About the Paper
Soil heterotrophic microbes, as both ‘decomposers’ and ‘contributors’ of soil organic carbon (SOC), play a central role in SOC’s transformation and long-term preservation. Microbial CUE is a key parameter to characterize microbial efficiency of OC conversion and is widely used in soil carbon models to describe microbial transformation processes. As mentioned above, POM and MAOM have been highlighted as two distinct SOC functional pools with different compositions, formation pathways and environmental persistence. In some next-generation models (such as the Millennial model), similar microbial CUE is assumed for POM and MAOM. However, several recent studies suggest that microbial CUE may be higher in MAOM than POM. However, empirical studies comparing microbial CUE in POM versus MAOM are lacking, hampering soil and ecology scientists’ mechanistic understanding of ecological patterns and processes from the organismic to the ecosystem scale based on soil microbial physiology and different soil functional pools.
The corresponding author Xiaojuan Feng (left) and the first author Lixiao Ma (right) of the paper (Credit: Xiaojuan Feng)
About the researchIsolating POM and MAOM is the key to this study. They tried various methods. Ultimately, Milli-Q water rather than chemical dispersant or density agent (e.g., sodium metatungstate) was used to minimize potential disturbance to soil microbes by any residual chemicals. Although this approach may not completely separate POM and MAOM, significant differences were observed in organic matter composition, microbial community composition, and phosphorus availability between POM and MAOM in this study, indicating that the employed method distinguished POM and MAOM fractions at least partly. They isolated POM versus MAOM from 25 soils from natural forests and grasslands with divergent edaphic properties and compared their microbial CUE using incubation with 18O-labeled water. In contrast to their expectation, microbial CUE did not consistently differ between POM and MAOM, because dissolved nitrogen availability relative to microbial stoichiometric requirement, the best predictor of microbial CUE, was similar in MAOM and POM. However, CUEPOM/CUEMAOM of the same soil showed a large variability among sites and decreased with increasing phosphorus limitation in POM relative to MAOM. This result highlighted potential contrasts in microbial CUE between soil pools under strong phosphorus limitation. Such inferences deserve attention under potentially increasing phosphorus limitation induced by nitrogen deposition.
Sampling sites and process of the experiment (Credit: Xiaojuan Feng)
Collection and pretreatment of soil samples (Credit: the authors)
Quantifying microbial CUE using incubation experiments with 18O-labeled water (Credit: the authors)
Xiaojuan Feng was awarded the Chinese Young Female Scientist Award (Credit: Xiaojuan Feng)
About the authorInitially driven by a profound curiosity and a deep-seated passion for nature, Xiaojuan Feng has been fascinated by various insects and plants, planting a seed for ecology in her heart since childhood. Upon entering university, she discovered the boundless mysteries awaiting exploration in soil. From that moment on, she embarked on her journey into soil ecology research. She joined the Institute of Botany, Chinese Academy of Sciences in 2013, leads the “Carbon Cycling and Organic Geochemistry Research Group” and currently serves as the Deputy Director of the Institute of Botany. Her research focuses on biogeochemistry and global change, employing molecular-level geochemical methods such as biomarkers and compound-specific 14C to investigate the cycling of SOC in terrestrial-river systems and its response to global change. She often tells her students, “Choices matter more than efforts!”
Members of FengLab (Credit: Xiaojuan Feng)
Like the blog post? Read the paper here.