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Aims <p>Shrub encroachment is an important ecological process affecting grassland soil carbon (C) cycling. However, the response of plant- and microbial-derived C to shrub encroachment and their contributions to soil organic carbon (SOC) remain controversial.</p> Methods <p>Here, a field survey was conducted across four alpine meadow sites on the Tibetan Plateau, encompassing five degrees of shrub encroachment (~ 0%, ~ 25%, ~ 50%, ~ 75%, and ~ 100%). Lignin phenols and amino sugars served as biomarkers to explore the effects of progressive shrub encroachment on C derived from plants and microbes, and their respective roles in contributing to SOC.</p> Results <p>The increasing shrub encroachment led to a significant 8.0% reduction in total amino sugar accumulation, with glucosamine (GluN) and muramic acid (MurA) decreasing by 8.6% and 17.6%, respectively. Shrub encroachment also reduced lignin phenols by 56.0%, with cinnamyl-type phenols decreasing most (59.5%). Moreover, the concentrations of plant (16.7–8.6&#xa0;g&#xa0;kg<sup>−1</sup>), fungal (21.7–19.3&#xa0;g&#xa0;kg<sup>−1</sup>), bacterial (8.9–7.2&#xa0;g&#xa0;kg<sup>−1</sup>), and microbial-derived (30.6–26.5&#xa0;g&#xa0;kg<sup>−1</sup>) C all exhibited declining trends as shrub encroachment intensified in grasslands. Compared to the high and stable contribution of microbial derived C to SOC, plant-derived C exhibited a notable decline of 48% as a result of shrub encroachment, with this process being primarily influenced by variations in soil pH.</p> Conclusion <p>Our findings suggest that even in the absence of significant changes in topsoil SOC content, the differential accumulation of plant- and microbial-derived C in shrub-encroached grasslands provides critical insights for improving predictions of SOC persistence and storage in alpine grasslands.</p>

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Grassland shrub encroachment generates divergent contributions of plant- and microbial-derived carbon to soil organic carbon

  • 期刊论文

  • 发表日期：

    2025年8月11日

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  • Xuewei Wang,
  • Pengfei Zhang,
  • Yuntao Zhang,
  • Jianing Wang,
  • Peng He,
  • Lina Zheng,
  • Ning Ling,
  • Zhaoming Wang

摘要

Aims

Shrub encroachment is an important ecological process affecting grassland soil carbon (C) cycling. However, the response of plant- and microbial-derived C to shrub encroachment and their contributions to soil organic carbon (SOC) remain controversial.

Methods

Here, a field survey was conducted across four alpine meadow sites on the Tibetan Plateau, encompassing five degrees of shrub encroachment (~ 0%, ~ 25%, ~ 50%, ~ 75%, and ~ 100%). Lignin phenols and amino sugars served as biomarkers to explore the effects of progressive shrub encroachment on C derived from plants and microbes, and their respective roles in contributing to SOC.

Results

The increasing shrub encroachment led to a significant 8.0% reduction in total amino sugar accumulation, with glucosamine (GluN) and muramic acid (MurA) decreasing by 8.6% and 17.6%, respectively. Shrub encroachment also reduced lignin phenols by 56.0%, with cinnamyl-type phenols decreasing most (59.5%). Moreover, the concentrations of plant (16.7–8.6 g kg−1), fungal (21.7–19.3 g kg−1), bacterial (8.9–7.2 g kg−1), and microbial-derived (30.6–26.5 g kg−1) C all exhibited declining trends as shrub encroachment intensified in grasslands. Compared to the high and stable contribution of microbial derived C to SOC, plant-derived C exhibited a notable decline of 48% as a result of shrub encroachment, with this process being primarily influenced by variations in soil pH.

Conclusion

Our findings suggest that even in the absence of significant changes in topsoil SOC content, the differential accumulation of plant- and microbial-derived C in shrub-encroached grasslands provides critical insights for improving predictions of SOC persistence and storage in alpine grasslands.