The Record Of Fire Events And Environmental Evolution Since The Holocene In The Subei Basin

Environmental evolution in Holocene is closely linked to the development of human society, and it is particularly important to study the environment evolution of Holocene in a comprehensive and meticulous manner. Fire caused by natural factors and human factors has became an important factor to control the evolution of ecological environment. Therefore, it is significant for us to study the fire activities and also discuss the relationship between fire activities, human activities and even the shift of environmental.After detailed field investigation, this paper selects the Gangxi section located in Subei Basin as the obgect of study. The Gangxi section is located near the settment center of Subei Basin,and the deposition is continuous and stable,which is a good environmental information carrier. In this study, the upper 500cm part of the section was selected to study, and sample was taken at 2cm interval, a total of 250 samples were collected. The chronological sequence was established by the comprehensive application of AMS14C dating and climate stratigraphy. Through the determination and analysis of particle size, Rb/Sr, SiO2/Al2O3, Total organtic carbon(TOC)and Black Carbon(BC), this paper reveals their variation in the sediments of the section of Gangxi, and then according to the chronological sequence and combined with previous research results as well as historical document literature, discuss the fire activities and climate evolution since the Holocene in the Subei Basin, and further explore the relationship between fire activities, human activities and the shift of environmental.The main conclusions are as follows:1. The BC deposition record of the Gangxi section can directly reflect the history of fire activities in the Subei Basin,the result is as follows: 12821?10430cal a.B.P., the fire activities rarely occurred; 10430-7520cal a.B.P., the fire activities happened frequently;7520-4523cal a.B.P., the fire activities were significantly reduced;4523?1180cal a.B.P., the fire activities were the most frequent and intense.2. Since the Holocene , the evolution of climate in the Subei Basin has experienced the following four periods: 12821 ?10430cala.B.P.,corresponds to transitional period from the end of the last glaciation to the Holocene, was a cold and dry climate, and gradually became warm and humid; 10430-7520cala.B.P.,corresponds to the early Holocene,was a relatively warm and humid climate but unstable, and was an obvious sea level rising stage;7520-4523cala.B.P., corresponds to the Holocene Megathermal,was the most humid and warmest during the whole Holocene,and transgression reached maximum; 4523?1180cala.B.P.,corresponds to the late Holocene,climate change from warm and humid to temperate and slightly dry,the environment of this area was fresh lake.3. Gangxi section revealed climate change not only has a better comparability with the neighboring areas of existing researeh Qingfeng section, but also has a good coincidence with the cave stalagmites of sanbaodong record and NGRIP ice core record. This indicates that the climate change in Subei Basin in eastern China not only has significant regional characteristics but also has great correlation with the global climate change.4. In Subei Basin, there is a good coupling between the fire activities, climate evolution and human activities:in the transitional period from the end of the last glaciation to the Holocene(12821 ?10430cala.B.P.),climate was still cooer,fire activities rarely occured due to less combustible; in early Holocene(10430-7520cal a.B.P.), the possibility of occurrence of fire activities was improved, because the combustible enough. In addition,climate was unstable,which exacerbated the occurrence of fire activities; during the Holocene Megathermal(7520?4523cala.B.P.),was a warm and humid climate, rich precipitation made humidity of air big and combustible absorbed more water. During this period, human life and production methods were mainly collected, fishing, hunting.Under the influence of transgression,people left their place, so the possibility of the occurrence of fire activities was very litter; in late Holocene (4523-1180cala.B.P.),fire activities were the most frequent and intense. One reason is that was temperate and slightly dry climate, which provided more opportunities for the occurrence of fire activities. Another reason is that as the increase of population and the development of agricultural civilization,the large scale of human activities greatlly exacerbated man-made fire activities.