晚全新世以来云南高山湖泊有机与无机碳埋藏特征及气候响应机制

Characteristics and mechanism of organic and inorganic carbon burial and the climate response of Late Holocene alpine lakes in Yunnan, SW China

  • 摘要: 高山湖泊作为高海拔生态系统碳循环的敏感指示器,其碳埋藏过程对理解区域及全球碳循环、揭示气候与湖泊生态系统间关键耦合机制具有重要的意义。本研究通过对滇西北高山区域丁公错3500 cal.aBP以来湖泊沉积物中多环境代用指标的综合分析,结合高精度AMS14C测年及主成分分析等,揭示了晚全新世以来气候驱动下的云南高山湖泊有机碳和无机碳埋藏的动态特征及驱动机制。研究结果表明,在35001100 cal.aBP,Rb/Sr和Zr/Sr指示的流域相对较低的侵蚀强度与有机碳持续降低相对应。而自700 cal.aBP以来,高山区域温度升高削弱了冻融作用,加剧湖泊流域侵蚀与营养输入,驱动有机碳回升及无机碳波动。同时,丁公错沉积物有机碳和无机碳埋藏的显著负相关(R=−0.48,P<0.001),体现了气候调控下的高山湖泊“双碳权衡”的埋藏机制。其有机碳埋藏主要受总氮含量累积(R=0.72,P<0.001),降水(R=0.38,P<0.001),流域侵蚀(Rb/Sr(R=0.31,P<0.001),Zr/Sr(R=0.28,P<0.001))的正向驱动,反映了陆源有机碳的输送作用;无机碳埋藏与中值粒径(R=0.47,P<0.001)和碳氮比(R=0.31,P<0.001)呈显著正相关,且与流域侵蚀(Rb/Sr(R=−0.65,P<0.001),Zr/Sr(R=−0.59,P<0.001))呈显著负相关,表明其为流域侵蚀和外源输入主导的埋藏过程。研究结果阐明了垂直地带性框架下的气候-侵蚀-营养盐耦合驱动机制,这将为高海拔生态脆弱区应对气候变暖的适应性管理以及高山区碳汇评估提供科学依据。

     

    Abstract: As a sensitive indicator of carbon cycle in alpine ecosystems, the carbon burial process in alpine lakes is of great significance for understanding the regional and global carbon cycle and revealing the key coupling mechanism between climate and lake ecosystems. The dynamics and driving mechanism of organic carbon (OC) and inorganic carbon (IC) burial in alpine lakes in Yunnan Province (SW China) driven by climate since the late Holocene were revealed by comprehensive analysis on multi-environmental proxies from lake sediments since 3500 cal.aBP in the Dinggong Co Lake, NW Yunnan, combined with high-precision AMS14C dating and principal component analysis. Results show that between 3500~1100 cal.aBP, the erosion intensity of the basin was relatively low as indicated by Rb/Sr and Zr/Sr, which corresponded to the continuous decrease of OC. Since 700 cal.aBP, temperature rose in the alpine region, which weakened the freeze-thaw effect, promoted the erosion and nutrient input into the lake basin, and drove the OC recovery and IC fluctuation. Meanwhile, the significant negative correlation between organic carbon and inorganic carbon burial in Dinggong Co Lake sediments (R=−0.321, P<0.001) reflects the burial mechanism of “double carbon balance” in the alpine lakes under climate regulation. The burial of organic carbon was mainly driven by the accumulation of total nitrogen (R=0.644, P<0.001) and C/N (R=0.385, P<0.001), reflecting the transport of terrestrial organic carbon. Inorganic carbon burial was significantly positively correlated with the median particle size (R=0.490, P<0.001), and was inhibited by precipitation dilution (R=−0.355, P<0.001), indicating that the burial process was dominated by watershed erosion and exogenous input. This study clarified the driving mechanism of climate-erosion-nutrient coupling in the vertical zonation framework, and provided a scientific basis for the adaptive management of alpine ecologically fragile areas in response to climate warming and the assessment of carbon sinks in alpine areas.

     

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