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中国东部较高空间分辨率表土总有机质(TOC)碳同位素,以及从中抽提的来自陆生高等植物的具有明显奇偶优势的长链正构烷烃碳同位素,具有一致的空间变化趋势和显著的正相关关系.两者都在北纬31°～40°之间较为偏正,而在该区域以北和以南都较为偏负,这一结果与中国东部表土植硅体碳同位素研究结果是一致的,共同指示了中国东部地区北纬31°～40°之间区域的水热组合条件较适合C4植物的生长.来自华北同一研究地点相同植被类型(草地)下的12个表土,其总有机质碳同位素和长链正构烷烃碳同位素变化幅度都很小,两者之间的差异也很稳定.这些研究结果说明,在中国东部地区,表土TOC碳同位素和长链正构烷烃碳同位素可以同等有效的作为上覆植被中C3/C4植物比例的指示器.同时,中国东部表土两类碳同位素的对比表明,-22‰和-32‰可以作为纯C4和纯C3植被下表土长链正构烷烃碳同位素组成的端元值(C27,C29,C31加权平均值)而应用于估计历史时期C4植物的相对生物量贡献。
The TOC isotopic compositions of the TSP in the eastern part of China, as well as the carbon isotopes of long-chain n-alkanes with obvious odd-even advantages derived from higher terrestrial plants, show a consistent trend of spatial variation and significant positive , Both of which are more positive in the latitude 31 ° ~ 40 ° and more negative in the north and south of this region, which is consistent with the carbon isotopic study of phytoplankton in the eastern part of China. Which indicated that the combination of hydrothermal conditions in the areas between 31 ° and 40 ° N latitude in eastern China is more suitable for the growth of C4 plants.From 12 topsoil under the same vegetation type (grassland) in North China, the total organic carbon isotope and The variation of carbon isotopes of long-chained n-alkanes is very small and the difference between them is also very stable.These results show that TOC carbon isotopes and long-chained n-alkanes carbon isotopes are equally effective in the eastern China The ratio of C3 / C4 plants in the overlying vegetation shows that both -22 ‰ and -32 ‰ can be used as the subsurface soil of pure C4 and pure C3 vegetation N-alkanes end membered carbon isotope composition values (C27, C29, C31 weighted average) and applied to the estimated relative biomass contribution C4 plants historical period.