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<p>Lacustrine sedimentary nitrogen isotope (δ<sup>15</sup>N) records offer crucial insights into the impacts of regional anthropogenic activities and environmental changes on nitrogen cycling dynamics within the context of global climate change. This study summarized δ<sup>15</sup>N data from 27 Chinese lakes since 1750 CE, categorizing them into Types I (eastern and southern China, densely populated area) and II (Northwestern China [NWC] and the Qinghai-Tibet Plateau [QTP], sparsely populated area). The results showed pronounced regional and temporal variability in nitrogen isotope trends. Type I lakes exhibited a significant positive δ<sup>15</sup>N deviation post-1950 CE, linked to population growth (<i>r</i>=0.91, <i>p</i>&lt;0.01) and economic development, with mitigation after 2000 CE likely due to enhanced environmental policies. Conversely, Type II lakes showed coherent δ<sup>15</sup>N variations with natural climate change from 1750 to 1950 CE, followed by a post-1950 CE decline exceeding natural variability. This shift is attributed to a “warming-wetting trend” in NWC and the QTP, which presumably increased terrestrial productivity, altered nitrogen cycling, and enhanced <sup>15</sup>N-depleted nitrogen input via surface runoff. Rising temperatures may have enhanced the activity and abundance of nitrogen-fixing microorganisms, jointly driving a negative δ<sup>15</sup>N shift. This study highlights climate conditions and anthropogenic activities as key drivers of nitrogen cycle perturbations in China, with their influences varying spatiotemporally, thereby providing crucial insights into the nitrogen cycling dynamics in Chinese lakes.</p>

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Divergent nitrogen isotope trends in Chinese lake sediments since the mid-Qing Dynasty: Influencing factors and implications

  • 期刊论文

  • 发表日期：

    2025年5月26日

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  • Yang Pu,
  • Qiaqia Huang,
  • Xueqiong Wei,
  • Mengmeng Zhang

摘要

Lacustrine sedimentary nitrogen isotope (δ15N) records offer crucial insights into the impacts of regional anthropogenic activities and environmental changes on nitrogen cycling dynamics within the context of global climate change. This study summarized δ15N data from 27 Chinese lakes since 1750 CE, categorizing them into Types I (eastern and southern China, densely populated area) and II (Northwestern China [NWC] and the Qinghai-Tibet Plateau [QTP], sparsely populated area). The results showed pronounced regional and temporal variability in nitrogen isotope trends. Type I lakes exhibited a significant positive δ15N deviation post-1950 CE, linked to population growth (r=0.91, p<0.01) and economic development, with mitigation after 2000 CE likely due to enhanced environmental policies. Conversely, Type II lakes showed coherent δ15N variations with natural climate change from 1750 to 1950 CE, followed by a post-1950 CE decline exceeding natural variability. This shift is attributed to a “warming-wetting trend” in NWC and the QTP, which presumably increased terrestrial productivity, altered nitrogen cycling, and enhanced 15N-depleted nitrogen input via surface runoff. Rising temperatures may have enhanced the activity and abundance of nitrogen-fixing microorganisms, jointly driving a negative δ15N shift. This study highlights climate conditions and anthropogenic activities as key drivers of nitrogen cycle perturbations in China, with their influences varying spatiotemporally, thereby providing crucial insights into the nitrogen cycling dynamics in Chinese lakes.