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<p>Anthropogenic elevated atmospheric carbon dioxide (eCO<sub>2</sub>) increases carbon (C) availability to plants. Whether ecosystems store or release this additional C depends on the balance between net primary production (NPP) and soil respiration, where eCO<sub>2</sub>-stimulated NPP can be constrained by the provisioning of nutrients by microbial decomposers. Ecosystems gradually become more phosphorus (P)-limited as weathering of primary minerals and occlusion of available phosphate increase with age, making plant-microbial competition for P a potential key driver of the fate of C in mature ecosystems under eCO<sub>2</sub>. In a P-limited mature forest (EucFACE, Australia), we found that soil microbial growth was primarily limited by C, but that P was the secondary limiting resource. This suggests that increased plant-derived C inputs under eCO<sub>2</sub> could relieve microbial C limitation and intensify microbial demand for P. Surprisingly, a decade of eCO<sub>2</sub> instead <i>exacerbated</i> microbial C limitation. We posit that a fast growing copiotrophic decomposer community under eCO<sub>2</sub> required more C. This shift also resulted in exacerbated microbial P limitation under eCO<sub>2</sub>. These together primed microbial use of fresh litter inputs, truncating the ecosystem P cycle, and explaining the observed faster turnover of organic matter and more intense competition for P between microbes and plants under eCO<sub>2</sub>.</p>

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Strengthened resource limitation driven by accelerated microbial growth dampens response to elevated CO2 in a mature forest

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月16日

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  • Mingyue Yuan,
  • Catriona A. Macdonald,
  • Lettice C. Hicks,
  • Johannes Rousk

摘要

Anthropogenic elevated atmospheric carbon dioxide (eCO2) increases carbon (C) availability to plants. Whether ecosystems store or release this additional C depends on the balance between net primary production (NPP) and soil respiration, where eCO2-stimulated NPP can be constrained by the provisioning of nutrients by microbial decomposers. Ecosystems gradually become more phosphorus (P)-limited as weathering of primary minerals and occlusion of available phosphate increase with age, making plant-microbial competition for P a potential key driver of the fate of C in mature ecosystems under eCO2. In a P-limited mature forest (EucFACE, Australia), we found that soil microbial growth was primarily limited by C, but that P was the secondary limiting resource. This suggests that increased plant-derived C inputs under eCO2 could relieve microbial C limitation and intensify microbial demand for P. Surprisingly, a decade of eCO2 instead exacerbated microbial C limitation. We posit that a fast growing copiotrophic decomposer community under eCO2 required more C. This shift also resulted in exacerbated microbial P limitation under eCO2. These together primed microbial use of fresh litter inputs, truncating the ecosystem P cycle, and explaining the observed faster turnover of organic matter and more intense competition for P between microbes and plants under eCO2.