Stoichiometric shifts in surface soils over broad geographical scales: evidence from China's grasslands

Authors

  • Yuanhe Yang,

    Corresponding author
    1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China
    2. Department of Ecology, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China
    • Correspondence: Yuanhe Yang, State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.

      E-mail: yhyang@ibcas.ac.cn

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  • Jingyun Fang,

    1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China
    2. Department of Ecology, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China
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  • Chengjun Ji,

    1. Department of Ecology, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China
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  • Arindam Datta,

    1. Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
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  • Pin Li,

    1. Department of Ecology, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China
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  • Wenhong Ma,

    1. College of Life Science, Inner Mongolia University, Hohhot, China
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  • Anwar Mohammat,

    1. Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Ürümqi, China
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  • Haihua Shen,

    1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China
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  • Huifeng Hu,

    1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China
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  • Benjamin O. Knapp,

    1. Department of Forestry, University of Missouri, Columbia, MO, USA
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  • Pete Smith

    1. Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
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  • Editor: Ian Wright

Abstract

Aim

The identification of stoichiometric flexibility is crucial for understanding carbon–nitrogen–phosphorus (C–N–P) interactions and ecosystem dynamics under a changing environment. However, current evidence of stoichiometric flexibility mainly comes from manipulation experiments, with little evidence from large-scale observations.

Location

Alpine and temperate grasslands across northern China.

Methods

Using soil profiles derived from a historical national soil inventory and a contemporary regional soil survey across China's grasslands, we examined temporal changes in topsoil C:N:P ratios over recent decades.

Results

Topsoil C:N ratios of five major grassland types exhibited some flexibility but did not show significant changes over the sampling interval. Non-significant changes in topsoil C:N ratios were observed both in alpine grasslands on the Tibetan Plateau and in temperate grasslands on the Inner Mongolian Plateau. Consistent with the relatively stable C:N ratios, the slope of the soil C–N stoichiometric relationship did not differ significantly between the two sampling periods. Soil N:P ratios in the surface layer increased significantly over the sampling interval, however, with an overall increase of 0.60 (95% confidence interval 0.58–0.62). A larger increase in soil N:P ratio was found in temperate grasslands on the Inner Mongolian Plateau than in alpine grasslands on the Tibetan Plateau. Moreover, the slope of the soil N–P stoichiometric relationship in these grassland ecosystems became steeper over the sampling interval.

Main conclusions

These results demonstrate the stability of topsoil C:N stoichiometry but variability in N:P stoichiometry over broad geographical scales, highlighting that soil C and N are tightly coupled, but N and P tend to be decoupled under a changing environment.

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