天目山泥炭类脂物记录的微生物特征和植被演替

为进一步了解泥炭中微生物特征和植被的变化,对采自浙江天目山的样品进行了类脂生物标志物与有机碳同位素(δ13Corg)的测定。有机碳δ13Corg值整体偏负,显示C3植物占优势的特点。正构烷烃的分布特征表明,大多数样品来源于陆生高等植物和低等菌藻类生物,其中高碳数正构烷烃主要以C29为主峰,显示植被类型以木本植物为主,但草本植物的相对比例也发生了多次变化,且这种变化与有机质的相对贡献量密切相关。在深度100~68cm,不同来源的有机质,特别是低等菌藻类的相对贡献量都相对较少;在深度68~30cm,低等菌藻类生物的贡献逐渐变大;而表层泥炭的有机质主要来源于高等植被,菌藻类的输入较少。泥炭有机碳同位素与类脂生物标志物的综合特征表明,该区植被经历了几次明显变化,并据此可将研究区中全新世以来环境演化分为早(4100~3200aB.P.)、中(3200~700aB.P.)、晚(700aB.P.以来)三个环境演化阶段,其结论与前人的环境演化与全球气候变化研究具有较好的可比性。

Microbial charaeteristics and vegetation changes as recorded in lipid biomarker of Tianmushan peat bog

Lipid biomarker and organic carbon isotope were presented for identifying the microbial characteristics and paleovegetation changes of Tianmushan Area, Zhejiang Province, China, since the middle Holocene. Our results showed that organic carbon isotopic values (δ13Corg) ranged from -26.51‰ to -30.44‰, with an average value of -28.49‰, evidently indicating the predominance of C3 plants in this area since the formation of peat. The results from lipid biomarkers denoted a mixed organic contribution from lower and higher plants. The small molecules dominated by C17 were mainly from algae and bacteria, whereas the heavy-molecular-weight homologues (>C21) were chiefly from higher plants. Lipid analysis of peat profile revealed the carbon number distributions of n-alkanes, varying from C15 to C33, having a distinct odd-over-even predominance and a unimodal distribution in partial samples peaking primarily at C29 in the woodlands. The paleovegetation changes in relation to relative organic contribution can hereby be clearly detected by combining variations of C27, C29 and C31. We also found that the contribution of organic matter was largely from the higher plants below 68 cm. In relatively deeper part of the peat profile, more inputs were probably from the algae and bacteria, whereas the organic compositions were primarily from high vegetation and largely reduced contribution from algae and bacteria in the upper peat section. Combined analysis of biomarker and organic carbon isotope signature consequently revealed three remarkable paleoenvironmental stages, including the early stable era between 4100 and 3200 a B.P., the middle changeable period from 3200 to 700 a B.P., and a relatively warm stage since 700 a B.P. In addition, our results were well in line with the pertinent research results in the study area, thereby complementing molecular data in paleoclimate studies and providing a useful basis for comparing global changes.