| Ching River is located in the semi arid and semi humid monsoon environmental sensitive area of China,and between the northern nomadic zone and dry farming zone.The landscape change is one of the most sensitive areas affected by the global climate change and human factors,and the frequent activities of human beings have a wide and profound impact on the ecological environment in the region since the holocene.As one of the earliest tools for environmental management,wildfire is not only affected by the changes of monsoon climate and vegetation biomass,but also reflects the changes of human land use and cultural characteristics.In this paper,using the related records of black carbon and many other environmental proxies to explore the effect of evolution of wildfires and human activities on the Gaoling area since the Holocene yangguanzhai,this understanding of the region has an important significance in fire history,ecological environment evolution and cultural development of human society.Shaanxi Gaoling yangguanzhai profile records the development of cultural relics miaodi Gou culture settlement period,which is the earliest city of our country village,through a lot of field investigation,the main archaeological sites in the Loess Plateau according to distribution characteristics,respectively.The magnetic susceptibility,black carbon,total organic carbon,organic carbon isotope and chemical elements analysis and determination,to reveal the structure changes of society and human land use yangguanzhai site area of the impact on the surrounding environment and its response to climate change;the results show that:(1)During the late glacial and early Holocene(～8 500a B.P.),magnetic susceptibility showed low values(78.57×10-8m3·kg-1),total of organic carbon(TOC)showed low values(0.15～19.36%),organic carbon of isotope 13C biased,this stage of black carbon and fine granular charcoal concentration is low,the coarse charcoal(>50um)concentration appears small fluctuations(250.19粒/g),showed that the arid climate area of the lower reaches of the Jinghe River Basin cold,have C3 herbs in desert steppe landscape,regional wildfire events happen sometimes.Limited C3 vegetation biomass inhibited the spread of fire in this region(2)The mid Holocene(8 500～3100a B.P.),magnetic susceptibility values showed a high value(144.18×10-8m3·kg-1),total organic carbon(TOC)was higher(22.63～55.43%),organic carbon isotope 13C showed a partial trend shows that the climate was warm and humid,with C4and C3 were mainly herbaceous woody plants in the forest steppe landscape formation.Since 8000 years ago,the concentration of carbon has shown a downward trend,increased by seasonal precipitation,thus inhibiting the probability of fire in a wide range.However,the 6 000～5000a B.P.carbon black and charcoal concentration peak(0.573mg/g and 480.38 grain/g)P,Mn,Zn phase elements showed a peak(at the same time,the concentration of P was 2490.45ppm,the background value),the archaeological record shows that found widespread Yangshao Miaodigou culture/period Banpo four culture culture period"ashable layer"and Jomon pottery diameter of several 1～2cm in the section 120～150cm layer,which may be related to the stage of Neolithic human activities such as fire burning and farmland,at the earliest Chinese North City settlement scale;5 500-5 000 a B.P.,magnetic susceptibility values show low value(as low as 144.18 ×10-8m3.kg-1),the leaching coefficient shows a low value(0.79),Rb/Sr(2.74),showed that the high ratio of the study area coincided with the drought and flood peak period of the period,soil Erosion has intensified,and urban ditches,flood control facilities and farmland have been repeatedly persecuted by floods and droughts.During the 5 000～4000a B.P.,the total organic carbon(TOC)decreased to 0.309%,the content of P decreased to 1197.48ppm,and the concentration of black carbon and carbon decreased gradually,showing low values(0.263mg/g and 81.06 grain/g).It shows that the ecological environment in this area has deteriorated further and the population has moved out.The urban settlement began to decline,resulting in a decrease in the level of anthropogenic biomass combustion at this stage.(3)The late Holocene(3 100a B.P.～now),magnetic susceptibility values are relatively low(the lowest value reached 54.44 ×10-8m3·kg-1),climate became drought and cold further,1 500～1000a B.P.,black low carbon content(BC-char0.148～0.376mg/g),showing a clear downward trend in biomass combustion.This may be because the land in this area has been reclaimed,and the dry farming landscape has been basically built up.The close relationship between fire and human activities in the Jinghe River Basin of the millennial scale shows that since 2000 nearly changes in land use and human settlements development of the city by the future fire ecology and monsoon climate interaction results.There are 17 pictures,5 tables,117 references. |
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