Holocene Records Of Black Carbon In The Loess And Paleo-soil Profiles And It's Environmental Changes In Longdong Region

Longdong area in the northern of Loess Plateau,semi and semi humid monsoon environment sensitive zone,it is Chinese traditional agricultural region and the animal husbandry regional convergence zone,more interference effects in the history of human activity on the area affected by human land use,also the landscape changes also easily by the effects of global climate changes,and it is one of the most sensitive area of global climate changes.This area is an important area,which is the first place for human to carry on the activities of agriculture and animal husbandry.Therefore,this paper through a large number of field observation selected Longdong area ofthe northern of Loess Plateau,two Holocene Loess-paleosol profiles,respectively for Gansu Heshui Ma Jia Cun(MJC)profile and Pengyang County in Ningxia Changcheng Village(CCC)section,respectively on two profiles were high resolution sampling,and sample profiles were susceptibility,TOC,charcoal,black carbon,geochemical elements and so climate surrogate markers of indoor analysis and determination,to probed since Holocene north of the Longdong Loess Plateau Ecological Environment Evolution and human activities and climate changes between the relationship.The research results show that:(1)Charcoal,black carbon,magnetic susceptibility,total organic carbon(TOC)and geochemical elements climate proxies for laboratory analysis and statistics of two Holocene loess paleosol profile of the northof Longdong area.The results show that the climate of the last glacial and early Holocene(a BP 11500?8500)was cold and dry,and the concentration of black carbon and carbon dust is low,and the vegetation biomass is the main limiting factor for the occurrence and spread of biomass burning in this stage;Holocene suitable period(8500?3100 a BP),due to the monsoon,resulting in the region affected by the warm and humid conditions of climate control,charcoal and black carbon concentrations showed a downward trend,show that under natural conditions of biomass burning incident began to decrease,the stage of a large number of seasonal precipitation become inhibit the main factors affecting the biomass burning events;Stage of late Holocene(3100 a BP?so far),black carbon and charcoal concentration curves generally showed a downward trend,but in the Sui and Tang Dynasties,a large number of immigrants influx increased due to land reclamation,and the "Medieval Warm Period" and in Ming and Qing Dynasties "Little Ice Age" climate change impact,black carbon and charcoal concentration appears repeatedly low frequency peak value change,so nearly 2000 years of biomass combustion characteristics by climate and human activities combined driving force control.(2)The research on the relationship between the Holocene biomass burning events and human activities and the ecological environment evolution,the results showed that,during the Holocene suitable period,in the warm and wet climate and superior hydrothermal conditions,well-developed Heilu soil,this traditional rainfed farming in the period of prosperity and development,the frequent biomass burning incident was mainly caused by human activities.The late Holocene,because of more arid climate,combined with increased human burning of forests land reclamation and other activities,resulting in Longdong area north of soil erosion and ecological destruction was serious,and the northern part of the loess high terrace land reclamation scale had already reached saturation and therefore dating back 1500 years,human burning open waste reclamation Zaotian scene had tended to lower levels.