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成土碳酸盐同位素对重建古气候、古生态的演化有重要意义,近些年来用它来讨论古季风的演化。其原因在于不同类型光合作用途径的植被使碳同位素产生不同的分馏作用,C4植物富集~(13)C,而C3植物则相对富集~(12)C,成土碳酸盐扩δ~(13)C值主要反映C4和C3植被的生物量之比。C4与C3草本植物相比,前者更适合季风气候湿热的季节中生长。温带草原中,较早生长的C3草本植物在夏季时往往让位于C4草本植被,于是C4植被就成为盛行季风气候的标志,它反映了亚洲季风的开始或增强。此外,15 Ma以来冬雨盛行的地中海气候带C3植被始终占统治地位。由此可见,C4植被草原扩展时的成土碳酸盐δ~(13)C是讨论季风气候演化的有效方法。
Carbonatite isotopes are important for reconstructing paleoclimate and paleoecology. They have been used to discuss the evolution of paleok monsoons in recent years. The reason for this is that different types of photosynthesis lead to different fractionation of carbon isotopes. C4 plants are enriched in ~ (13) C and C3 plants are relatively enriched in ~ (12) C, (13) The value of C mainly reflects the biomass ratio of C4 and C3 vegetation. C4 is more suitable for season growing in monsoon climate than in C3 herb. Of the temperate grasslands, the earlier growing C3 herbaceous plants often give way to C4 herbaceous vegetation in summer, so C4 vegetation became a symbol of prevailing monsoon climate, which reflects the beginning or enhancement of the Asian monsoon. In addition, the Mediterranean climate C3 vegetation has always dominated the winter rain since 15 Ma. It can be seen from the above that the evolution of δ ^ (13) C in the evolution of the C4 vegetation steppe is an effective way to discuss the evolution of the monsoon climate.