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首页> 外文期刊>Journal of quaternary science: JQS >Climate and vegetation variations since the LGM recorded by biomarkers from a sediment core in the northern South China Sea
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Climate and vegetation variations since the LGM recorded by biomarkers from a sediment core in the northern South China Sea

机译：自南海北部沉积物核心的生物标志物记录了LGM以来的气候和植被变化

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Variations in stable carbon isotopic compositions of n-alkanes (δ~(13)C_(alk)) and n-alkane proxies (CPI, C_(31)/C_(27) and ACL) from core MD05-2905 (20° 08.17′ N, 117° 21.6′ E) in the northern South China Sea (SCS), provided evidence of biological responses on adjacent land areas in the form of changes in terrestrial vegetation and provenance of the remains of land plants during and since the Last Glacial Maximum (LGM). Decreased values of n-alkane proxies and δ~(13)C_(alk) over the last 28ka marked the transition from glacial to interglacial conditions and indicated a greater extent of herbaceous vegetation at the LGM than present and an increased abundance in woody vegetation during the Holocene. Relatively larger δ~(13)C_(alk) values at the LGM indicated that n-alkanes of terrestrial herbs in the sediment core were not only from the leaf waxes of C_3 plants, such as herbs of Artemisia, growing on proximate parts of the exposed continental shelf, but also from C4 grasses likely from subtropical parts of southeastern China and Taiwan Island. Reconstructed sea-surface temperatures (SSTs), based on U_37~K'} data from the same core, revealed that temperatures were ~3°C lower than present during the LGM, with abrupt variations during both glacial and interglacial periods. During the LGM, lower temperature and sea level and greater aridity relative to present resulted in an expansion of herbaceous vegetation over an enlarged extent of exposed continental shelf. Following deglaciation, warming and enhanced summer monsoonal activity led to increased humidity and to an expansion of woody vegetation (mostlyC_3 plants) during the Holocene. Results also revealed rapid oscillations in C_(31)/C_(27) ratios over millennial scales, with lower values associated with cold stages. These low C_(31)/C_(27) ratios indicated increased input of woody plant material possibly from more extensive gallery forest and greater transport of their plant debris to the coring site, perhaps facilitated by enhanced runoff under a strengthened Northern Hemisphere winter monsoon during short-duration cold events.
机译：MD05-2905核心（20°08.17）的正构烷烃（δ〜（13）C_（alk））和正构烷烃代理（CPI，C_（31）/ C_（27）和ACL）的稳定碳同位素组成的变化南海北部（SCS）的′N，117°21.6′E）以末次冰河期间及之后的陆地植被变化和陆上植物遗迹的形式提供了对相邻陆地生物反应的证据最大值（LGM）。最近28ka的正构烷烃代理值和δ〜（13）C_（alk）的下降标志着从冰川向冰间条件的过渡，表明LGM上的草木植被比现在更大，并且在此期间木本植物的丰度增加全新世。 LGM处的δ〜（13）C_（alk）值相对较大，表明沉积物核心中的陆生草本植物的正构烷烃不仅来自C_3植物的叶蜡，例如蒿的草本植物，还生长在其附近。暴露的大陆架，也来自中国东南部和台湾岛的亚热带地区的C4草。基于来自同一岩心的U_37〜K'}数据，重建的海面温度（SSTs）显示，温度比LGM期间的温度低约3°C，在冰川期和冰川间期都有突变。在LGM期间，相对于目前而言，较低的温度和海平面以及更大的干旱导致草本植物在裸露的大陆架扩大范围内扩展。冰川消融后，全新世期间变暖和夏季季风活动增强，导致湿度增加和木质植被（主要是C_3植物）的扩张。结果还表明，在千禧年尺度上，C_（31）/ C_（27）比率快速振荡，而与寒冷阶段相关的值较低。这些低的C_（31）/ C_（27）比率表明，木本植物材料的输入可能来自更宽阔的林场森林，以及其植物碎屑向取心地点的更多运输，这可能是由于北半球冬季季风增强期间径流增加所致。短暂的寒冷事件。

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