Microbial metabolism and necromass mediated fertilization effect on soil organic carbon after long-term community incubation in different climates

Abstract

Understanding the effects of changing climate and long-term human activities on soil organic carbon (SOC) and the mediating roles of microorganisms is critical to maintain soil C stability in agricultural ecosystem. Here, we took samples from a long-term soil transplantation experiment, in which large transects of Mollisol soil in a cold temperate region were translocated to warm temperate and mid-subtropical regions to simulate different climate conditions, with a fertilization treatment on top. This study aimed to understand fertilization effect on SOC and the role of soil microorganisms featured after long-term community incubation in warm climates. After 12 years of soil transplantation, fertilization led to less reduction of SOC, in which aromatic C increased and the consumption of O-alkyl C and carbonyl C decreased. Soil live microbes were analyzed using propidium monoazide to remove DNAs from dead cells, and their network modulization explained 60.4% of variations in soil labile C. Single-cell Raman spectroscopy combined with D2O isotope labeling indicated a higher metabolic activity of live microbes to use easily degradable C after soil transplantation. Compared with non-fertilization, there was a significant decrease in soil α- and β-glucosidase and delay on microbial growth with fertilization in warmer climate. Moreover, fertilization significantly increased microbial necromass as indicated by amino sugar content, and its contribution to soil resistant C reached 22.3%. This study evidentially highlights the substantial contribution of soil microbial metabolism and necromass to refractory C of SOC with addition of nutrients in the long-term.

Estuarine plastisphere as an overlooked source of N2O production

“…1a ). Thus the ratio of (C–D)/(C–D + C–H) is a quantitative indicator for microbial phenotypic activity 15 , 42 . We acquired the Raman spectrograms of 40–50 microbial cells in each plastisphere and bulk water after 30 days, and calculated their (C–D)/(C–D + C–H) ratios.…”

“…The generated spectra were subsequently analyzed in LabSpec-5 software (HORIBA Jobin-Yvon) with baseline correction and normalization. Peak intensities of Raman bands assigned to C–D (2040–2300 cm −1 ) and C–H (2800–3100 cm −1 ) were obtained to estimate (C–D)/(C–D + C–H) ratios 42 .…”

Thermal adaptation occurs in the respiration and growth of widely distributed bacteria

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The microbial decomposition of soil organic matter can produce up to 13.5 Gt CO 2 year −1 (Eswaran et al, 1993), which is comparable with the demand of terrestrial plants (Gruber & Galloway, 2008;Ni et al, 2021). Bacterial species are abundant in soils, and these bacteria play a key role in soil carbon (C) cycling and nutrient exchange (Delgado-Baquerizo et al, 2018;Janssen, 2006).

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Distinct stabilization characteristics of organic carbon in coastal salt‐affected soils with different salinity under straw return management

“…This is further supported by our finding that POC had a higher contribution rate to the increased TOC in medium‐salinity soils (approximately 35%, which could be calculated as the ratio of the increased POC to the increased TOC) than that in low‐salinity soils (close to zero). As microbial metabolic products or necromass formed during plant residue decomposition are considered to facilitate mineral‐organic interactions and contribute substantially to the stable soil C pool (Ni et al, 2021), the lower stability of the straw returning–induced SOC increment in medium‐salinity soils could partly be attributed to the slower straw decomposition rate. Increasing soil salinity has been reported to decrease straw decomposition rate (Xie et al, 2017), mainly because of its lessening effect on microbial biomass and C‐degrading enzyme activities (Chen, Wang, et al, 2021; Xie et al, 2017).…”