The Characteristics And The Paleoenvironment Information Of Biomarker In The Soil Over The Heshang Cave And Stalagmite In Qingjiang, Hubei Province

The biomarkers have been widely used to explore the globe change such as paleoclimateand paleoenvironment based on the analyses of marine sediments, lacustrine sediments, snowand ice, peat, stalagmite, aerosol. They have made a series of important progress in the researchof globe change.The stalagmites, as the products of interactive processes among the atmosphere, hydrosphere,biosphere and lithosphere have five advantages:(1)has the abroad distribution; (2) high precisiondating; (3) has the long span of time; (4) the relatively continuous record; (5) the least possibilityof alternation after deposition. The former research has approved the indexes carbon and oxygenisotope, trace element, lamina thickness; gray level could reflect the past globe change. But thebiomarkers have been ignored by many people which contain much of biologic sourceinformation. So bring the biomarker into the research of soil and stalagmite has great signi-ficance.By using gas chromatography-mass spectrometry (GC-MS), a series of biomarkers wereidentified from the soil collected over the Heshang cave and the stalagmite collected in theHeshang cave in Qingjiang, Hubei Province.The n-alkanes mainly distribute from C₂₅ to C₃₃ in carbon number, with a maximum at C₃₁ insoil samples. They have a strong odd-over-even carbon number predominance. This character-istics represent an input mainly from higher plants.The lipid parameters, including CPI_h, (carbon preference index) R_h/l (ratio of lower-tohigher-molecular-weight homologues) and ACL (average chain length) show the comparabletrend with depth, probably reflecting the vegetation change and the microbial degradation.Microbial activities play an important role in the formation and evolvement of soil in theKarst area. In order to further investigate the characteristics of microbial activity in the Karst soilprofile, we analyze the biomarker and organic carbon in the soil samples. The ¹³C_org valuesindicate the C₃ plants have been predominant in this area since the soil formed. The lipid parameters, including carbon preference index (CPI_h), ratio of lower- to higher-molecular-weight homologues (R_h/l) and average chain length (ACL), show comparable trendswith depth, largely consistent with the organic carbon isotope. This probably is restricted bymicrobial activities, thus reflecting microbial degradation in the soil profile. The relativeabundance ratio of the fatty acid of C_16:1 and C_16:0 has a significance correlation with theextractable organic matter. It shows the low concentration of carbon source could limit themicrobial activity in the Karst soil. In contrast the biomarker in stalagmite with soil we find thefatty acid has the same model, but the abundance of high carbon become higher, it reflects thevegetation input in the soil. However the abundance of lower carbon alkanes is plenty in thestalagmite, so have much microorganism input.The conventional way to solve the stalagmite sample is solvent method, but this methodneeds large quality of samples. This is not propitious to the demand of high resolution. In orderto improve the time resolution, we use the new method—acid digestion method, which couldimprove the temporal resolution greatly. Using the acid digestion method we gain a great deal ofpalaeoclimate and paleoenvironment information which contain in the biomarker of alkanes andn-alkanoic acid in the stalagmite.The h/h+1 value could indicate the vegetation quantity in the whole ecosystem and thecomposition diversity index (CDI) could reflect the ecosystem change in the Qingjiang River.Compare to the two curves we could find the ecosystem has the Millennial-scale fluctuation andthe higher plant has the important function in the ecosystem. The ecosystem has a short cycle andhas a long cycle. Anytime of the ecosystem state is the summation of the two cycles. Besides theCDI value accord with the surface sea temperature (SST) change of the North Atlantic Ocean,this could reflect the long cycle variety oftbe ecosystem is controlled by the climate change.The ratio of the unsaturated acid to saturated acid indicate the cold event, every cold eventcorrespond to the rise of the oxygen isotope value. The early cold event in the Holocene isintense but the frequency is low, and the late cold event in the Holocene became weaken but thefrequency is higher, especially in the recent 2000a. The cold events records from the 8700a tonowadays in the middle of the Yangtze River could compare to the other regions, but has somedifferences. This could show the district difference in the Qingjiang drainage area. The strongestcold event may happen in the 8000a, this result is not accordant with the conventional recognizeof the "8.2Ka cold event", the concrete reasons need more deep discuss.The carbon isotope value of plant assemblage cellulose in the Hongyuan peat bog from theTibet Plateau, and the oxygen isotope value record from Dongge Cave, southern China and thebiomarker indexes in the stalagmite of the Heshang cave in Qingjiang drainage area all record aserious change process of climate and environment. This event accords with the record of thesouth China ancient lake water level and the archeology. It symbolize to the end of the period ofHolocene optimum in Yangtze River. The emergence of civilization, one of great marks in thehistory of human evolution, remains one of the hottest topics in the world. Many theories havebeen put forward to explain its causes and mechanisms. Although the development of complexsociety has its own developmental traces, the role of environment change in the development of civilization should not be ignored. Compare to the different geology records we could make aconclusion that the climate change may be the most important reason for the variety of the modeof production and the advance of the productivity, lead to the collapse of Neolithic cultures andthe emergence of Chinese civilization during the same period.The ratio of (C₂₇+C₂₉+C₃₁) and C_12-20 which represents the relative input quantity of thehigher plants to microorganism and the bacteria, algae has the same trend with the plankticforaminifer of the Globigerina bulloide percentage change which could indicate the Indianmonsoon and the organic carbon in ocean deposition in South China Sea which could indicatethe East Asian Monsoon. The three curves show that both the East Asian monsoon and the Indianmonsoon have influence in the middle of the Yangtze River. It indicates the solar radiation→monsoon variety→climate transformation→organism adaptation model.The basic theory of the globe change which be used in the stalagmite biomarker researchcomes from the biology (include microbiology, vegetation physiology and so on) and the ecology.We should also combine this research to many subjects in new means and thoughtway such asgeography, climatology, and archeology. As a new way of globe change research, it will have theabroad applications in globe change research.