Knowledge Resource Center for Ecological Environment in Arid Area
| 青藏高原不同气候区四醚膜类脂物GDGTs指标高度关系及其影响因素 | |
| 其他题名 | Altitude effect of GDGTs proxy and its influencing factors in different climatic zones of the Tibet Plateau |
| 陈炽皓 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 杨建平 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 青藏高原的隆升是晚新生代以来全球气候变化的重要驱动因素，同时，也强烈影响了亚洲季风系统的形成和演化。近年来，尽管对青藏高原古高度的研究取得了一些突破性的认识和进展，高原地表抬升的时空格局仍存在很大的争议：氢氧同位素方法重建的古高度相对生物证据要高。因此，仍然需要应用多学科多种高度计综合恢复青藏高原不同块体的古高度，互相验证，更精确有效地约束高原隆升历史。甘油二烷基甘油四醚（GDGTs）是一类微生物的细胞膜脂化石，表征其分子组成结构特征的甲基化指标（MBT）和环化指标（CBT）联合被广泛用于重建陆地古温度，国内外不同山体表土的广泛研究证实MBT/CBT记录的温度通过气温直减率转换可以用来定量重建古高度。但是由于微生物对环境响应复杂，pH值和降水量被认为是影响MBT/CBT指标重建温度精度的主要因素；同时诸如植被类型、土壤类型、微生物群落、山形等因素的差异造成MBT/CBT指标的温度转换函数存在区域性。基于新近分离的6甲基GDGTs提出了如MBT’5ME，MBTmr等温度指标，这些指标在青藏高原不同区域的适用性尚需研究。本文研究了青藏高原边缘湿润—半干旱的高原南部（喜马拉雅南坡、察隅到拉萨断面）、湿润—半湿润的高原东部（龙门山）、半湿润—半干旱的高原西北部（塔吉克斯坦帕米尔高原西坡）和半干旱—干旱的高原东北部（祁连山、昆仑山、阿尔金山）4个不同气候区210个表层土壤的GDGTs分布，其中118个样品分离了6甲基GDGTs。评价GDGTs各温度指标在青藏高原不同区域重建高度的适用性，分析pH值和降水量对表土MBT/CBT指标温度重建的影响，建立GDGTs温度指标的区域转换函数，同时考察GDGTs的pH指标和古水文指标，加深对潜在的古高度定量重建新指标体系GDGTs在青藏高原地区的理解。结果如下：（1）MBT/CBT温度指标仅在高原南部的喜马拉雅南坡断面可以直接应用。无论在干旱还是湿润区，酸性土壤和碱性土壤的MBT值都表现出对温度梯度的响应速率不同，导致在相对高温（如，>0°C）时，碱性土壤MBT值偏低，从而低估温度。排除碱性土壤数据的高原南部以及东部相对低温的高海拔处（>3km）可以使用MBT/CBT指标。高原东北部干旱区和高原西北部高海拔碱性土壤中，MBT/CBT重建的温度出现反高度现象。（2）Peterse等人2012年建立的MBT/CBT全球土壤温度转换函数温度重建精度相对较高，但是重建的气温直减率偏低，应用该函数重建古高度时应参考现代过程中计算温度的气温直减率范围。Günther等人2014年建立的青藏高原湖泊沉积物转换函数因为表现了特殊的温度与CBT正相关关系和高CBT权重，可以用来重建出现反高度现象地区的温度高度。使用多元线性回归法和逐步选择回归法（SSM）分别建立了高原南部喜马拉雅区域、酸性土壤以及混合低温样品、高原东北部CBT异常样品的MBT/CBT和SSM温度转换函数。（3）建立了5，6甲基相关的温度指标各温度指标MBT’5ME，MATmr，MATmrs，Index1，Index2，MBT5/6等的区域转换函数。但是，各指标重建温度的相关性相对低于酸性土壤MBT/CBT指标，说明还受到了其他因素的影响。其中MBT’5ME适用范围最广；MBT’5ME在高原东北部冷干区，重建温度系统高估，在高原西北部半湿润区表现为系统低估。而在高原西北部东断面，各指标无法有效重建温度，可能由于山谷地形影响。 （4）根据上述结论，GDGTs指标重建古温度/高度时，需要考虑古环境pH值和古水文条件。青藏高原GDGTs的pH指标CBT’，CBT’’，CBT5ME，CBT’5ME，IBT，IR6ME，IRIIa’，IRIIIa’，rCBT可以用来重建古pH值，但在pH>8和pH<5时需要谨慎。IR6ME大于0.5时，MBT’可以用来重建古降水量。BIT和Ri/b能识别相对较干的环境，BIT<0.93只出现在年降水量MAP<1200mm时，Ri/b>0.3时只出现在MAP<1000mm时。在高原东北部干旱区，BIT、Ri/b和CBT可以定量重建小于400mm范围的古MAP。 |
| 英文摘要 | Tibetan Plateau (TP) uplift has changed the pattern of Asian atmospheric circulation, strengthened the formation and evolution of the Asia monsoon system, and caused the drying of the Asian inland since the late Cenozoic. Although much progress, including some breakthroughs, in our understanding of the evolution of TP paleoelevation have been made in recent years, the spatial-temporal pattern of surface uplift remains controversial. Especially, stable isotopes from paleosols generally yield much higher paleoelevations than those based on fossils. Therefore, additional paleoelevation data from different areas, obtained using multi-paleoaltimeters, is required to resolve the forms and processes of TP uplift and extension more precisely. Glycerol Dialkyl Glycerol Tetraether lipids (GDGTs) is a kind of microbial cell membrane lipid fossils, the methylation index (MBT) and the cyclization index (CBT), which characterize the structural characteristics of its molecular composition, are widely used to reconstruct the terrestrial paleo-temperature. A wide range of studies have confirmed that the branched GDGTs (brGDGTs) MBT/CBT effect temperatures (MBT/CBT–MAT) can be used to quantitatively reconstruct paleoelevation. However, the strong spatial heterogeneity highlights the necessity for regional calibrations of brGDGT variations with temperature. Furthermore, because of the complicated response of microorganism to the environment, pH and aridity influence the accuracy of MBT′/CBT–MAT. Based on the newly isolated 6-methyl GDGTs, the temperature indexes such as MBT’5ME, MBTmr were proposed, but their applicability require further validation in different regions of the TP.In this paper, we present the GDGTs distributions in 210 surface soils from four different climatic zones on the TP, including the wet-semi-arid Southern TP (the Himalayan southern slope, Zayu-Lhasa section), the wet-subhumid Eastern TP (Longmen Mountains), the semi-wet and semi-dry northwestern TP (western slope of Tajikistan pamirs), and the semiarid-arid northeastern TP (Qilian Mountains, Kunlun Moutains and Altun Mountains). 118 of them were separated 6-methyl GDGTs. To evaluate the applicability of MBT/CBT–MAT, we analyze the effects of pH and aridity on MBT/CBT–MAT, establish the regional soil calibration, and investigate the pH and paleohydrology index of GDGTs. The main conclusions are summarized as follows: (1) MBT/CBT–MAT can be directly applied only in the South Himalayan Transect. Whether in dry or wet areas, both the acidic and alkaline soil MBT values showed a different response rate to the temperature gradient, which results in a low soil MBT value at relatively high temperature (eg., >0°C), thus underestimates temperature. When excluding the alkaline soil in southern and eastern TP at high elevations (>3 km), MBT/CBT index can be used. Alkaline soil MBT/CBT–MAT values show the "inverse altitude effect" from the arid northeastern TP and the high elevation sites of northwestern TP. This is maybe that when MBT ratio is low, CBT values were positively correlated with temperature, which result that MBT/CBT–MAT regional calibrations can not be used, due to it is negatively correlated with CBT conventionally. (2) MBT/CBT global soil temperature calibration established by Peterse et al. (2012) is relatively higher accuracy in temperature reconstruction, but the temperature lapse rate reconstructed is lower. The application of this function to reconstruct paleoelevation should use the modern temperature lapse rate. Günther et al. (2014) established the lake sediment transfer function of TP, due to the high weight of CBT, and special positive correlation between temperature and CBT, it can be used to reconstruct paleoelevations where the MBT/CBT–MAT values show the "inverse altitude effect". Thus, using the multiple linear regression method and the stepwise selective regression method, we establishthe MBT/CBT and SSM temperature transfer functions for the Himalayan region, the acidic soil and mixed samples at low temperature and the CBT anomaly samples in the Northeastern TP, respectively.(3) We established the regional transfer function of each 5,6 methyl-related temperature index, such as MBT’5ME, MATmr, MATmrs, Index 1, Index 2, MBT5/6. The correlation of the reconstructed temperature of each index is relatively lower than that of the acidic soil MBT/CBT, suggesting effect of other factors. MBT’5ME is the most widely used. MBT’5ME–MAT overestimates the temperature in cold and dry areas northeastern TP, while underestimates in semi-humid northwestern TP. It is not applicable in northeastern TP due to their valley lattice. (4) According to above conclusions, pH value and paleohydrology in sediments should be considered when we use brGDGTs MBT/CBT–MAT to reconstruct palaeotemperature/elevations. pH index of GDGTs, such as CBT’, CBT’’, CBT5ME, CBT’5ME, IBT, IR6ME, IRIIa’, IRIIIa’, rCBT, can be used to reconstruction sedimentary pH value, but need to be careful when pH>8 and<5 in TP. When IR6ME is greater than 0.5, MBT’ can be used to reconstruct paleohydrology. BIT and Ri/b can identify relatively aridity, and BIT<0.93 only occurs when MAP<1200 mm, Ri/b>0.3 only occurs when MAP<1000 mm. In the arid northeastern TP, BIT, Ri/b and CBT can quantitatively reconstruct paleohydrology with MAP less than 400 mm. |
| 中文关键词 | GDGTs ; 古高度计 ; 青藏高原 ; 土壤 |
| 英文关键词 | GDGTs，Paleoaltimeter，Tibetan Pleatau，Surface Soil |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院青藏高原研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287899 |
| 推荐引用方式 GB/T 7714 | 陈炽皓. 青藏高原不同气候区四醚膜类脂物GDGTs指标高度关系及其影响因素[D]. 中国科学院大学,2017. |
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