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https://doi.org/10.5194/bg-2019-351
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-351
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 30 Oct 2019

Submitted as: research article | 30 Oct 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

How deep do we dig for surface soil? A comparison of patterns of microbial C : N : P stoichiometry between topsoil and subsoil along an aridity gradient

Yuqing Liu1,2,*, Wenhong Ma3,*, Dan Kou2,4, Xiaxia Niu2,3, Tian Wang2,4, Yongliang Chen2, Dima Chen2, Xiaoqin Zhu2, Mengying Zhao2,4, Baihui Hao2,3, Jinbo Zhang1, Yuanhe Yang2, and Huifeng Hu2 Yuqing Liu et al.
  • 1School of Geography Science, Nanjing Normal University, Nanjing 210023, China
  • 2State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
  • 3Department of Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
  • 4University of Chinese Academy of Sciences, Beijing 100049, China
  • *These authors contributed equally to this paper.

Abstract. Microbial stoichiometry and its driving factors play crucial roles in understanding the balance of chemical elements in ecological interactions and nutrient limitations along aridity gradients. However, little is known about the variation in these features along aridity gradients due to the lack of comprehensive field investigations. Additionally, previous studies focused on the surface soil (0–10 or 0–20 cm); however, the minimum sampling depth for surface soil could impact the results of the vertical distribution of microbial stoichiometry. In the present study, we measured the variation in microbial stoichiometry, examined the major influential factors (climatic, edaphic and biotic factors) along an aridity gradient and determined whether the sampling depth affected microbial C : N : P stoichiometry. We found that the microbial C : N (topsoil: 6.59; subsoil: 6.83), C : P (topsoil: 60.2; subsoil: 60.5) and N : P ratios (topsoil: 9.29; subsoil: 8.91) varied with soil depth and that the microbial C : N ratio significantly increased with soil depth. The microbial C : N ratio significantly increased with increasing aridity for both topsoil and subsoil, while the microbial N : P ratio decreased along the aridity gradient only for the topsoil), which implied that drought-stimulated microbes tend to be more N conservative, especially for the topsoil. Among all the factors, the soil organic carbon (SOC) content and fungi to bacteria ratio exerted the largest influence on the microbial C : N, C : P and N : P ratios at both soil depths, implying that the substrate supply and microbial structure together controlled the microbial stoichiometry. The results also revealed that the aridity index (AI) and plant aboveground biomass (AGB) influenced the C : N ratio in microbial biomass at both soil depths, and the effects of those factors decreased in the subsoil. The results of this study suggested that the flexibility of the microbial N : P ratio should be considered when establishing the minimum sampling depth in a vertical study. The present study also represented the first attempt to examine the patterns of soil microbial stoichiometry for different soil depth along an aridity gradient.

Yuqing Liu et al.
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Short summary
The microbial C : N ratio increased with aridity, while the microbial N : P ratio decreased with aridity, which implied that drought-stimulated microbes tend to be more N conservative. Among all examined ecological factors, substrate supply and microbial structure together controlled the microbial stoichiometry. Overall, these results illustrated N and P limitation in microbial biomass at deeper soil depths along aridity gradient and limited responses to ecological factors in the subsoil.
The microbial C : N ratio increased with aridity, while the microbial N : P ratio decreased with...
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