大九湖泥炭地现代植物不同组分的δ^18O及其古气候意义

CHARACTERISTICS OF δ^18O OF THE DIFFERENT COMPONENTS OF PLANTS AND IT＇S CLIMATIC SIGNIFICANCE IN THE DAJIUHU PEATBOG, CENTRAL CHINA

最初学者利用泥炭植物同位素重建气候变化是参考树轮的研究方法，而树轮中不同组分的同位素对气候变化的响应不同。泥炭地植物不同组分的同位素对气候的响应是否也存在差异，需要进一步探讨和研究。此外，不同泥炭地植物δ18O的气候学解译存在一定的争议，这些解译的差异要求我们在利用泥炭δ18O重建古气候时需结合泥炭地现代过程的监测。文章以中国东部季风区的大九湖泥炭地为研究区域，测试研究区现代植被α纤维素与综纤维素的δ18O，对比两者的分布特征及其在时间序列上的相关性，进而探讨它们对气候因子的响应程度。结果表明：大九湖泥炭地植物δ18O分布较离散，平均值为25.09‰，α纤维素的δ18O比综纤维素δ18O偏正0.79‰～1.06‰，两种组分的δ18O在季节变化序列上没有明显的相关性。通过与区域气候因子的对比，我们发现温度是影响该地区植物δ18O变化的主要因素，而且植物α纤维素的δ18O比综纤维素的δ18O对温度响应更敏感，植物α纤维素更适用于作为研究古气候变化的载体，这一结果为中国东部季风内将泥炭地植物α纤维素的δ18O作为温度变化的代用指标提供了实验支持。

Peat has been recognized as an important geological archive on the reconstruction of Late Quaternary climate change（especially the paleoclimatic changes during Holoence）. It is particularly suitable for isotopic geochemistry studies. At first, using plants stable oxygen isotope to reconstruct climate change was reference the tree ring study. The climate implications of stable isotope ratios in different components from tree ring vary locality. We should know that whether this phenomenon also exists in different components of stable isotope ratios peat plants. Besides, a comparison of different regions shows that the climate implications of the values of δ18O from peat plant cellulose vary with locality. The difference of interpretation about the significance of δ18O requires that we should provide modern process research about the peat bog when we use δ18O to reconstruct the palaeoclimate. The Dajiuhu peat（31°24＇～31°33＇N, 109°56＇～110°11＇E; 1730 m a.s.l.） is located in the west of the Shennongjia Forest District, Hubei Province, Central China. The wetlands are rich in biological species, giving priority to meadow vegetation and swamp vegetation and having well-preserved moss vegetation. We sampled modern plants from the Dajiuhu Basin, resulting in a total of 24 samples, mainly include Carex argyi, Sanguisorba officinalis, Polytrichum commune and Typha orientalis Presl. In this study, the δ18O values of different tissue components of plants in the Dajiuhu peatbog were analyzed, and correlation analysis was performed on climatic factors influencing the holocellulose and α-cellulose values of δ18O in plants of this area. The test results show that δ18O values of α-cellulose range from 21.08‰～29.09‰ and δ18O values of holocellulose range from 19.83‰～29.09‰. Values of δ18O are more dispersed in this area, with the average of 25.09‰. Carex plants have more enrichment of the heavy oxygen isotopes than the moss plants. On the basis of relative analyses, there were no significant correlations between α-cellulose and holocellulose in the time series. At the same time, the relationship between δ18O of α-cellulose and climate or environment factors was statistically significant. On the contrary, there were no significant correlations between holocellulose and climate or environment factors. The results indicate that temperature is a major factor influencing the values of δ18O in plants of this area. We found that δ18O of α-cellulose are more susceptible to climatic conditions. Therefore, the δ18O values of α-cellulose are more suited to study past climate changes. Our results confirmed previous argument that the δ18O values of peat cellulose could indicate the change in temperature in the monsoonal area of China.