Divergent accumulation of microbial necromass and plant lignin components in grassland soils

Tian Ma,Kaihui Li,Guohua Dai,Dima Chen,Wenxuan Han,Chao Liang,Zhiheng Wang,Bowei Feng,Yongfei Bai,Xiangyan Su,Huifeng Hu,Shanshan Zhu,Xiaojuan Feng

doi:10.1038/s41467-018-05891-1

Abstract

The means through which microbes and plants contribute to soil organic carbon (SOC) accumulation remain elusive due to challenges in disentangling the complex components of SOC. Here we use amino sugars and lignin phenols as tracers for microbial necromass and plant lignin components, respectively, and investigate their distribution in the surface soils across Mongolian grasslands in comparison with published data for other grassland soils of the world. While lignin phenols decrease, amino sugars increase with SOC contents in all examined grassland soils, providing continental-scale evidence for the key role of microbial necromass in SOC accumulation. Moreover, in contrast to clay’s control on amino sugar accumulation in fine-textured soils, aridity plays a central role in amino sugar accrual and lignin decomposition in the coarse-textured Mongolian soils. Hence, aridity shifts may have differential impacts on microbial-mediated SOC accumulation in grassland soils of varied textures.

Highlights

The means through which microbes and plants contribute to soil organic carbon (SOC) accumulation remain elusive due to challenges in disentangling the complex components of SOC
In the surface soil of Mongolian grasslands (Fig. 1a), amino sugars had an SOCnormalized concentration of 21–158 mg g−1 SOC (Fig. 1b; Supplementary Data 1), dominated by glucosamine
This is consistent with the literature data exhibiting a similar range of concentration in the surface soil of grasslands elsewhere[14,20,24,25] (18–155 mg g −1 SOC; full list of references in Supplementary Data 2; Supplementary Fig. 1)

Summary

Introduction

The means through which microbes and plants contribute to soil organic carbon (SOC) accumulation remain elusive due to challenges in disentangling the complex components of SOC. While microbial biomass has a fast turnover and constitutes a tiny fraction of SOC, microbial necromass is considered to be relatively stable[14] and accrue in the soil with iterative community turnover[4,11,13,15,16] This process, embedded in the microbial carbon pump originally put forward by marine researchers[17], is considered to be a key mechanism contributing to the persistence of organic carbon in soils as well[18,19]. Using statistical analysis encompassing similar environmental variables, we compare mechanisms regulating the accumulation of both biomarkers in the Mongolian grasslands and contrast environmental influences on amino sugar accrual in the coarse-textured Mongolian soils vs fine-textured grassland soils elsewhere This approach allows us to assess the large-scale distribution and preservation of microbial necromass vs plant lignin components in grassland soils spanning an unprecedented range of environmental gradients. Our results provide proof-of-concept evidence for the key role of microbial necromass in SOC accumulation and suggest that aridity shifts may have differential impacts on microbial-mediated SOC accumulation in grassland soils of varied textures

Methods

Results

Conclusion