Microbial stoichiometry overrides biomass as a regulator of soil carbon and nitrogen cycling

Abstract

Understanding the role of soil microbial communities in coupled carbon and nitrogen cycles has become an area of great interest as we strive to understand how global change will influence ecosystem function. In this endeavor, microbially explicit decomposition models are being adopted because they include microbial stoichiometry- and biomass-mediated mechanisms that may be important in shaping ecosystem response to environmental change. Yet there has been a dearth of empirical tests to verify the predictions of these models and hence identify potential improvements. We measured the response of soil microbes to multiple rates of carbon and nitrogen amendment in experimental microcosms, and used the respiration and nitrogen mineralization responses to assess a well-established, single-pool, microbial decomposition model. The model generally predicted the empirical trends in carbon and nitrogen fluxes, but failed to predict the empirical trends in microbial biomass. Further examination of this discontinuity indicated that the model successfully predicted carbon and nitrogen cycling because stoichiometry overrode microbial biomass as a regulator of cycling rates. Stoichiometric control meant that the addition of carbon generally increased respiration and decreased nitrogen mineralization, whereas nitrogen had the opposite effects. Biomass only assumed importance as a control on cycling rates when stoichiometric ratios of resource inputs were a close match to those of the microbial biomass. Our work highlights the need to advance our understanding of the stoichiometric demands of microbial biomass in order to better understand biogeochemical cycles in the face of changing organic- and inorganic-matter inputs to terrestrial ecosystems.

Fungal interactions reduce carbon use efficiency

“…among ruderal or stress‐tolerant wood‐decay fungi; Boddy ), the induced costs of interspecific interactions are likely to be less important that traditional ecological processes such as community turnover, differential resource use or facilitation (Allison ; Buchkowski et al . ; Maynard et al . ).…”

Topsoil and Deep Soil Organic Carbon Concentration and Stability Vary with Aggregate Size and Vegetation Type in Subtropical China

“…Due to the different stoichiometric ratios between microorganism and the substrate, the microbes will have different OC utilization efficiencies under different stoichiometric ratios of substrate for nutrient requirement [53,54], which may induce different OC mineralization. Manzoni et al [52]considered that stoichiometry controlled microbial carbonuse efficiency in soils and Buchkowski et al [55] reported that microbial stoichiometry overrode biomass as a regulator of soil carbon cycling. Therefore, the higher SOC min in CF than in BF in deep soil may be induced by the differences of nutrient concentration, C/P and N/P between two vegetation types, since P concentration was higher in CF and broadleaf litters with high N/P ratios accumulated in the BF [56].…”

Nitrogen recycling in coupled green and brown food webs: Weak effects of herbivory and detritivory when nitrogen passes through soil

“…We used soil samples from two, 2 cm in diameter and 5‐cm deep, soil cores for assays of initial extractable inorganic nitrogen and microbial biomass. These properties were measured using established laboratory methods (Buchkowski, Schmitz, & Bradford, ; Durán, Delgado‐Baquerizo, Rodríguez, Covelo, & Gallardo, ; Hood‐Nowotny, Umana, Inselbacher, Oswald‐Lachouani, & Wanek, ; Sims, Ellsworth, & Mulvaney, ).…”