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<p>The Xisha Islands accumulated significant amounts of phosphorus (P) due to seabird guano input. However, the seabird population has declined significantly in recent years as a result of climate change and human activities. As plant communities develop, significant amounts of organic matter and nitrogen were introduced into the soil through plant humus. To investigate the effects of different sources on the distribution of phosphorus fractions during the past ~1000 years of ecological evolution, we conducted <i>k-edge</i> x-ray absorption near-edge structural spectroscopy (XANES), sequential extraction, and <sup>31</sup>P nuclear magnetic resonance (<sup>31</sup>P-NMR) of soil phosphorus in two ornithogenic soil profiles from the Xisha Islands. Combining these methods, the results revealed that magnesium-bound phosphorus (Mg-P) in modern guano underwent mineralization after deposition, and its content decreased by &gt; 50%. Subsequently, it may be released and combine with the abundant calcium-bearing minerals to transform into calcium-bound phosphorus (Ca-P). The results of XANES and sequential extraction indicated that Ca-P dominated the soil phosphorus pool by up to 70%–90%. The distributions of total organic carbon, total nitrogen, and total phosphorus in the soil profile are consistent with the evolutionary characteristics of nutrient supply from guano or plant humus during historical periods. In addition, although plant humus has lower total phosphorus content than guano, it may be an important source of organic phosphorus for topsoil. This study provides insights into the evolution of coral island ecosystems by examining phosphorus fractions and sources of phosphorus and offers valuable references for understanding nutrient cycling on tropical coral islands.</p>

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Phosphorus fractions of ornithogenic soil profiles in coral islands using P k-edge XANES, sequential extraction, and 31P-NMR spectroscopy

  • 期刊论文

  • 发表日期：

    2025年11月24日

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  • Xianglong Xi,
  • Yongli Zhou,
  • Xueying Wang,
  • Zhangqin Zheng,
  • Yulu Xue,
  • Libin Wu,
  • Liqiang Xu,
  • Xiaodong Liu

摘要

The Xisha Islands accumulated significant amounts of phosphorus (P) due to seabird guano input. However, the seabird population has declined significantly in recent years as a result of climate change and human activities. As plant communities develop, significant amounts of organic matter and nitrogen were introduced into the soil through plant humus. To investigate the effects of different sources on the distribution of phosphorus fractions during the past ~1000 years of ecological evolution, we conducted k-edge x-ray absorption near-edge structural spectroscopy (XANES), sequential extraction, and 31P nuclear magnetic resonance (31P-NMR) of soil phosphorus in two ornithogenic soil profiles from the Xisha Islands. Combining these methods, the results revealed that magnesium-bound phosphorus (Mg-P) in modern guano underwent mineralization after deposition, and its content decreased by > 50%. Subsequently, it may be released and combine with the abundant calcium-bearing minerals to transform into calcium-bound phosphorus (Ca-P). The results of XANES and sequential extraction indicated that Ca-P dominated the soil phosphorus pool by up to 70%–90%. The distributions of total organic carbon, total nitrogen, and total phosphorus in the soil profile are consistent with the evolutionary characteristics of nutrient supply from guano or plant humus during historical periods. In addition, although plant humus has lower total phosphorus content than guano, it may be an important source of organic phosphorus for topsoil. This study provides insights into the evolution of coral island ecosystems by examining phosphorus fractions and sources of phosphorus and offers valuable references for understanding nutrient cycling on tropical coral islands.