The Relationship Between Environmental Evolution And Human Activity Of Vally District In The Northeast Margin Of Tibetan

This article selects Xiasunjiazhai section in the valley of the northeastern margin of Tibet plateau as the research object, and analyze the chromacity, particle size, magnetic susceptibility, kish carbon and sporopollen of the samples collected from the section, then selects four kish carbon samples in the depth of 106 cm, 160 cm, 174 cm and cultural layer of the profile to test their age. Two kish carbon samples in the 160 cm, 174 cm depth of the profile get conclusion, the correction of the calendar year are respectively 4675±105 cal.aBP, 4970±60 cal.aB.P.. One of the the remaining two don’t get conclusion because of amount of sample, the measured age of the other one is obviously older, so this paper give up them. It indicates that the culture type of the section is Majiayao’s early cultural. Among environmental indicators, the redness of chromacity index can well reveal the environmental evolution of research area, which can obtain the better consistency by comparing with other climatic indicators. The concentrations of kish carbon and pollen well reveals activities of Majiayao’s early cultural ancestor, which indicates that human activity had a great effect on the research area during 5000-4500 cal aB.P., the peak of the concentration of kish carbon appear during 5000-4800 cal aB.P., which indicates that the scale and intension of human activity is unparalleled. Pollen analysis reveals that the natural environment in the research area was temperate grassland that was dominant by artemisia in the early stage of Majiayao culture, the concentration of gramineae was rising in this period, which indicates that Ancestors mainly engaged in agricultural production mode that was dominant by crop farming. The increase of concentration of sporopollen also suggest that the scale and intensity of the ancestors activity in early stage of Majiayao culture increased. The decrease of trees percentage in the period may also reveal that under the influence of large-scale farming activities, due to the demand for farmland and other need, ancestor damaged the forest on a large scale. In addition, human production activities had a great impact on the particle size and magnetic susceptibility of the profile, which results in that the particle size and magnetic susceptibility are abnormal, can’t well reflect the environment evolution, but may reflect the interference of human activity on natural sedimentation process. The statistics of the date of 86 kish carbon and their cultural types of excavated sites in the northeast edge of the Tibet plateau found that the number of kish carbon increased than that of hunter-gather period in the northeast edge of the Tibet plateau during Majiayao’s early culture, but compared with Majiayao’s late culture, the statistical number of kish carbon still has very big disparity. The peak of the kish carbon and pollen concentration of this study section appeared in Majiayao’s early culture, which indicates the development of Majiayao’s early cultural ancestors and Majiayao late cultural ancestors was asynchronous and inconsistent on time, the ancestors in the study area developed earlier than that of other areas, earlier engaged in large-scale production.