PDF《植物叶蜡正构烷烃分子分布特征与植被类型的关系》

植物叶蜡正构烷烃分子分布特征与植被类型的关系 刘? 虎1,

2 ,刘卫国

1 (1.

中国科学院地球环境研究所 黄土与第四纪地质国家重点实验室,西安 710061;

2. 中国科学院大学,北京 100049) 摘? 要:正构烷烃是自然界中广泛分布的生物标志化合物,其链长及主峰碳常被用来指示古气候 和古植被变化.我们测定了贡嘎山、太白山和黄土高原地区

65 个植物样品叶蜡正构烷烃的分子 分布特征,并对

1232 个木本和草本植物(包括本实验的

65 个样品)的正构烷烃比值进行统计. 研究表明:木本和草本植物正构烷烃中 C29 和C31 含量基本均较高,其相对丰度变化很大,其中 木本植物主峰碳为 C27 或C29 的占 61.9%, 草本植物主峰碳为 C31 的占 65.2%. 三元相图分析也表明, 木本和草本植物 C

27、C29 和C31 的相对丰度重叠部分较大,而以 C

27、C29 和C31 为标准对木本和 草本植物进行判别分析的准确度为 69.5%.研究结果表明 C

27、C29 和C31 主峰碳丰度不能作为区 分木本和草本植物的有效指标.同样,利用 C31/C29 或C31/C27 也不能够区分木本和草本植物.我 们发现以 C33/(C33+C29)=0.30 为标准对木本和草本植物进行判别分析的准确度为 81.5%,而以 C33/ (C33+C27)=0.20 为标准对灌木和草本植物进行判别分析的准确度为 85.7%,表明某些正构烷烃比值 可能具有区分木本和草本植物的潜力,但结合

1232 个木本和草本植物数据统计发现,正构烷烃 比值不能有效区分木本和草本植物.因此,应谨慎利用正构烷烃主峰碳及比值进行植被恢复,这 可能为古气候和古植被重建提供必要的参考. 关键词:植物叶蜡;

正构烷烃;

植被类型;

碳链长度;

主峰碳 中图分类号:Q948??文献标志码:A??文章编号:1674-9901(2015)03-0168-12 Relationship of plant leaf wax n-alkanes molecular distribution characteristics and vegetation types LIU Hu1,

2 , LIU Wei-guo1 (1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'

an 710061, China;

2. University of Chinese Academy of Sciences, Beijing 100049, China) Abstract: The biomarkers n-alkanes are ubiquitous in nature environment. Its chain length and dominant carbon are commonly used to indicate the changes of paleoclimate and paleovegetation. Here we analyzed the distribution of plant leaf wax n-alkanes in

65 plant samples from the Gongga Mountain, Taibai Mountain and Chinese Loess Plateau in China and we also combined

1232 observations of grasses and woody plants, including the new data here, to examine the chain-length ratios of n-alkanes of different vegetation types. We found that: n-alkane distributions for grasses and woody plants showed high variabilities and only 61.9% woody plants were dominated by C27 or C29, while 65.2% grasses were dominated by C31. The accuracy was about 69.5% when C27, C29 and C31 were used as criterions to distinguish woody plants and grasses, and the large overlaps of ternary diagrams based on chain-length abundances also showed that it should be prudent to use n-alkane distributions as quantitative indicators. Similarly, C31/C29 or C31/C27 can'

t distinguish woody plants and grasses, either. Moreover, our results demonstrated that when C33/(C33+?C29)?=?0.30 or C33/(C33+?C27)?=?0.20

169 were taken as criterions to differentiate woody plants or shrubs from grasses, the accuracies were 81.5% and 85.7%, respectively, indicating that some chain-length ratios of n-alkanes could be used as effective indicators to some extent. However, results showed that the chain-length ratios of n-alkanes can'