The Contribution of Microorganisms to Soil Organic Carbon Accumulation under Fertilization Varies among Aggregate Size Classes

Jinjing Lu,Chunhua Gao,Fengjun Zheng,Mengni Zhang,Aurore Degré,Ahmed Ali Abdelrhman,Guopeng Liang,Shengping Li,Qiang Zhang,Xueping Wu,Jianhua Li,Dongsheng Jin

doi:10.3390/agronomy11112126

Abstract

Long-term fertilization alters soil microbiological properties and then affects the soil organic carbon (SOC) pool. However, the interrelations of SOC with biological drivers and their relative importance are rarely analyzed quantitatively at aggregate scale. We investigated the contribution of soil microbial biomass, diversity, and enzyme activity to C pool in soil aggregate fractions (>5 mm, 2–5 mm, 1–2 mm, 0.25–1 mm, and <0.25 mm) at topsoil (0–15 cm) from a 27-year long-term fertilization regime. Compared to CK (no fertilization management), NP (inorganic fertilization alone) decreased all of the microbial groups’ biomass, while NPS and NPM (inorganic fertilization plus the incorporation of maize straw or composted cow manure) significantly reduced this negative effect of NP on microbial biomass and increased the microbial contribution to C pool. The results show that microbial variables were significantly correlated with SOC content in >0.25 mm aggregates rather than in <0.25 mm aggregates. Fungal variables (fungal, AM biomass, and F/B ratio) and enzyme activities (BXYL and LAP) in >0.25 mm aggregates explained 21% and 2% of C, respectively. Overall, organic matter addition could contribute to higher C storage by boosting fungal community and enzyme activity rather than by changing microbial community diversity in macro-aggregates.

Highlights

Terrestrial soils contain approximately three times the stock of carbon (C) of the atmosphere; small changes in soil organic carbon (SOC) have a significant impact on climate change [1]
In NP, NPS, and NPM, there were no differences in SOC contents among all aggregates.Microbial biomass carbon (MBC) and ROC contents were significantly affected by fertilization and aggregate size, respectively (p < 0.001; Table 2)
The four treatments had no significant differences in ROC and MBC contents (Figure 1C,D)

Summary

Introduction

Terrestrial soils contain approximately three times the stock of carbon (C) of the atmosphere; small changes in soil organic carbon (SOC) have a significant impact on climate change [1]. Among the numerous drivers that regulate the SOC pool, microorganisms are essential for SOC turnover [2]. Microorganisms have been reported to promote the formation of macro-aggregates to physically protect C, and their residues are considered to constitute an important source of stable C. It is reported that over half of the cumulative CO2 -C emitted from soil was induced by microbial community [4]. As such, understanding the contribution of microorganissms and enzymes to the accumulation or consumption of SOC in soil is of utmost importance for regulating soil C and reducing the impact of CO2 on the climate system

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Conclusion