渝黔岩溶地区碳同位素的分布和变化特征及在古环境研究中的初步应用

发布时间：2018-03-03 08:22

本文选题：土壤　切入点：植被　出处：《西南大学》2016年硕士论文　论文类型：学位论文

【摘要】：洞穴沉积物作为古气候重建研究的重要载体之一,具有高精度定年、高分辨率连续记录等优势,可以提供大量古气候和古环境演变的信息。在石笋丰富的气候代用指标中,δ~(13)C记录因其影响因素复杂,加之地区差异和不同的沉积环境,对气候环境指示具有多样性,但其对古气候环境研究的重要意义不可忽视。为了正确解译碳同位素的环境指代意义,需要开展广泛的多点研究及重现性研究,系统研究不同洞穴碳同位素的垂直运移特征及主要影响因素,从而获取可靠的地表生态和环境变化信息。金佛山采集的24件植物样品的δ~(13)C平均值为-28.91%o,属于典型的C3植被类型。金佛山植被的δ~(13)C值比芙蓉洞山上植被的δ~(13)C偏重约3%o,主要是受生物物种和金佛山海拔高度的影响。植物叶片内外CO：分压比(Pi/Pa)会随海拔高度的增加而减小,植物δ~(13)C值相应偏重。除JF3剖面土壤有机碳δ~(13)C在深度55 cm处突然显著偏轻,JF1和JF2土壤有机碳δ18C均随着深度加深逐渐偏重,至一定深度后趋于稳定,这主要是受有机质分解过程中碳同位素分馏效应的影响。贵州六枝特区、关岭、盘县采集的植物样品中既有C3植被也有少量C4植物。由于受贵州地区生物种类、土壤环境等因素的影响,贵州石漠化地区植被δ~(13)C平均值均较重庆无石漠化地区的明显偏重。盘县地区中度石漠化的严酷环境和较高的海拔高度会影响植物Pi/Pa,导致该地区植被δ~(13)C值普遍偏重,另外,也会导致土壤有机质分解速率低,使盘县土壤剖面有机碳含量较其他剖面高。贵州三个采样点7个剖面的土壤有机碳含量大体都随深度的增大而降低。ND、LP1、LP2、LP3剖面土壤有机质δ~(13)C与有机碳含量变化关系对应明显,有机碳δ~(13)C值变化均随着深度增大而变重,达到最大之后又逐渐变轻趋于稳定,反映了该地区有机质的分解程度,而LZ1、LZ2、LZ3三个剖面土壤有机质δ~(13)C随深度的变化差异较大。贵州石漠化地区的土壤环境不利于微生物分解,碳同位素在植被和土壤之间的富集效应相对较弱。芙蓉洞洞穴水DIC-δ~(13)C表现出夏秋季偏重,冬春季偏轻的季节变化特征,对地表气候有明显滞后性,其主要受土壤CO_2浓度的影响,PCP作用、基岩溶解作用以及包气带的开放性等也是重要的影响因素。羊口洞洞穴滴水DIC-δ~(13)C普遍偏重,没有明显的季节变化。推测洞内强烈的脱气作用、土壤水中DIC-δ~(13)C与土壤CO_2的交换不充分可能是导致滴水DIC-δ~(13)C值偏重和没有季节性的主要原因,另外,土壤生物活动相对较弱以及基岩溶解也会对滴水DIC-δ~(13)C值偏重造成影响。纳朵洞各滴水点DIC-δ~(13)C值较偏重,季节性变化不明显,这可能与土壤水中DIC-δ~(13)C与土壤CO_2没有进行充分的交换有关。纳朵洞、芙蓉洞和羊口洞内外碳同位素在植被、土壤、洞穴滴水运移过程中的富集程度存在较大差异,可能与它们所处的地理环境、上覆土壤厚度、洞穴通风条件,各阶段分馏程度等因素有关。利用芙蓉洞FR5石笋的碳氧同位素数据重建了0-38 ka BP时段重庆地区亚洲季风强度和地表植被生物量以及地表生物过程的变化。FR5石笋的碳氧同位素在总体趋势上呈同向变化,但在某些时段呈负相关关系,石笋碳同位素反映有效湿度的变化。JFYK7石笋符合Hendy检验,可以用其碳氧同位素进行古气候重建。JFYK7石笋氧碳同位素对气候变化的响应几乎是同步的,指示了亚洲季风区37.8～78 ka BP时段的季风气候及地表植被生物量及生物过程的变化。两根石笋的δ~(13)C记录与其对应时期格陵兰冰芯NGRIP i记录以及亚洲季风区其他石笋的δ18O记录的对应关系基本一致,记录了一系列H事件和D/O事件发生通过对FR5和JFYK7石笋碳同位素变化驱动机制的研究,发现轨道尺度上,石笋的δ~(13)C值变化敏感地响应于太阳辐射能量变化,百年千年尺度上,北大西洋地区的温度变化改变海气环流格局,导致亚洲季风气候变化是影响FR5和.JFYK7石笋的δ~(13)C值变化的主要因素。北大西洋地区变冷,西风带将北大西洋地区变冷信息传递到西伯利亚东部,从而使西伯利亚高压增强,北半球温度降低,驱使热带辐合带(ITCZ)向南移动,亚洲夏季风减弱,响应H事件的发生。H事件发生时,亚洲夏季风减弱,气候干冷,植被生物量减小,土壤生物活动减弱,石笋δ~(13)C偏重；D/O事件时期,夏季风增强,气候暖湿,植被发育较好,石笋δ~(13)C偏轻。在更短的年际年内尺度上,与降水有关的岩溶地下水的流速与水-岩相互作用、CO_2脱气作用、先期碳酸盐沉积以及土壤CO_2的溶解等都可能对石笋的δ~(13)C变化产生了影响。JFYK7石笋氧碳同位素记录的72～75 ka BP左右的夏季风减弱和植被生物量减少以及土壤微生物活动减弱可能是由Toba火山喷发诱发的全球性降温引起的。JFYK7碳同位素与XY2石笋碳氧同位素对比说明,石笋δ~(13)C具有明显的地区差异性,因此利用石笋δ~(13)C进行古植被恢复时,需要结合本石笋δ18O记录以及其他石笋碳氧同位素进行对比,以确保古植被恢复的准确性。
[Abstract]:Cave deposits as an important carrier of the study of ancient climate reconstruction, with high precision dating, high resolution and continuous recording and other advantages, can provide a lot of paleo climatic and environmental evolution information. In the climatic indicators rich in stalagmite, 8 ~ (13) C records because of the complex factors, and regional differences and different the sedimentary environment, with diversity on the climate and environment of instructions, but their significance in Paleoclimate study can not be ignored. In order to correct the interpretation of carbon isotope environment refers to the meaning, need to carry out more extensive research and the reproducibility of the study, and the main influence factors of vertical migration characteristics of carbon isotopic system of different caves thus, to obtain the surface ecological and environmental change information reliable. 24 plant samples collected in Jinfo Mountain delta ~ (13) C average value is -28.91%o, C3 belongs to the typical vegetation. The vegetation in Jinfo Mountain Delta (~ 13) C value than the Furong mountain vegetation of 8 ~ (13) C on about 3%o, is mainly affected by the biological species and the Jinfo Mountain of elevation. Leaf inside and outside the CO: partial pressure ratio (Pi/Pa) increases with the altitude and decreases plant ~ (13) C delta values for the corresponding emphasis. In addition to soil organic carbon JF3 ~ (13) C profile at the depth of 55 cm suddenly significantly lighter, JF1 and JF2 18C were soil organic carbon delta with depth gradually tilted to a certain depth, and then tended to be stable, which is mainly influenced by the decomposition of carbon isotope fractionation of organic matter. The Guanling Guizhou Special Administrative Region Panxian, and collected plant samples with C3 vegetation also have a small amount of C4 plants. Due to species in Guizhou area, effects of soil environmental factors and vegetation in Guizhou rocky desertification area 8 ~ (13) C average value obviously higher than Chongqing non rocky desertification area in Panxian area. The moderate rocky desertification the harsh environment and High altitude will affect plant Pi/Pa, in the area of vegetation delta ~ (13) C values are generally biased, in addition, will also lead to soil organic matter decomposition rate is low, the soil organic carbon content in Panxian than other high profile. Increase the content of soil organic carbon in Guizhou three 7 sampling points with gross section the depth of the lower.ND, LP1, LP2, LP3 soil organic matter 8 ~ (13) C and organic carbon content corresponding to the variation of organic carbon was 8 ~ (13) C value changes with depth increases, reaches a maximum and then gradually become light stabilized, reflecting the degree of decomposition. In the area of organic matter and LZ1, LZ2, LZ3 three profile soil organic matter ~ (13) delta changes with the depth of C greatly. The soil environment in Guizhou rocky desertification area is not conducive to microbial decomposition, carbon isotope enrichment effect between vegetation and soil is relatively weak. Furong cave water DIC- Delta. (13 C) showed seasonal variation on summer and autumn, winter and spring are lighter, obvious on the surface climate, it is mainly affected by soil CO_2, concentrations of PCP, factors affecting the dissolution and the bedrock of the vadose zone openness is also important. How the cave drip water DIC- 8 ~ (13) C generally stresses, no significant seasonal variation. The strong that degassing effect, soil water in DIC- 8 ~ (13) C exchange and soil CO_2 may lead to inadequate water DIC- 8 ~ (13) C value and no emphasis on the main reason, seasonal and soil biological activity is relatively weak and the bedrock also on the DIC- Delta water dissolved ~ (13) C value on impact. The Naduo hole drip point DIC- 8 ~ (13) C value is biased, the seasonal variation is not obvious, which may be related to soil water DIC- 8 ~ (13) C and CO_2 in soil were not sufficiently exchange. Naduo hole Furong cave, and how Inside and outside of the tunnel and carbon isotope in vegetation, soil, there is a big difference between the degree of enrichment of cave drip during the process of migration, and their geographical environment, soil thickness, conditions of cave ventilation, relevant factors of each stage. The degree of fractionation of carbon and oxygen isotope data of FR5 from Furong cave reconstruction of the carbon and oxygen isotope changes.FR5 0-38 Ka BP stalagmite during Chongqing Asian monsoon intensity and vegetation biomass surface and the surface of biological processes was similar to the change in the overall trend, but there was a negative correlation between the carbon isotope of Stalagmite in some periods, anti.JFYK7 changes reflect the effective humidity in accordance with Hendy from test, which can be used to reconstruct the paleoclimate of carbon and oxygen isotopes.JFYK7 stalagmite oxygen carbon isotope response to climate change is almost synchronous, indicating the monsoon climate and surface Zhi Beisheng volume in Asian monsoon region from 37.8 to 78 Ka BP time Changes and biological process. Two stalagmites delta ~ (13) C record and the corresponding period of NGRIP I records of Greenland ice core and the relationship between other Stalagmite in Asian monsoon region Delta 18O record consistent record of a series of H events and the D/O events through the research of FR5 and JFYK7 from carbon isotope change driving mechanism. Find the orbital scale, a delta ~ (13) C sensitive response to changes in solar radiation energy, a hundred years of the Millennium scale, change the pattern of temperature change in the North Atlantic ocean atmosphere circulation area, leading to the Asian monsoon climate change is the effect of FR5 and.JFYK7 from 8 ~ (13) the main factors of C value change the North Atlantic cold westerlies will become cold North Atlantic region information transfer to Eastern Siberia, which makes Siberia high enhancement, the Northern Hemisphere temperature decreased, driven by the intertropical convergence zone (ITCZ) moving south Asian summer Monsoon, in response to.H events in the events of H, the Asian summer monsoon weakened, cold and dry climate, vegetation biomass decreased, soil biological activity decreased, 8 ~ (13) C stalagmite stress; D/O event period, enhanced summer monsoon, moist climate, vegetation growth is good, 8 ~ (13) C stalagmite lighter in the shorter the interannual scale, velocity and water - karst groundwater and precipitation related rock interaction, CO_2 degassing, early carbonate deposition and soil CO_2 are likely to dissolve from Delta ~ (13) C changes affected.JFYK7 stalagmite oxygen and carbon isotope records of 72~75 Ka BP. The weakening of summer monsoon and vegetation biomass reduction and soil microbial activity may be weakened by the Toba volcano induced global cooling caused by the carbon isotope of.JFYK7 and XY2 in stalagmite carbon and oxygen isotope comparison shows that delta ~ (13) C stalagmite has an obvious regional difference Therefore, when stalagmites delta ~ (13) C was used to restore palaeovegetation, we need to combine the stalagmite 18O record and other stalagmites carbon and oxygen isotopes to ensure the accuracy of ancient vegetation restoration.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P597;P532

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