中文摘要：

摘要：青藏高原主体海拔在4000m以上，4000m以上的人类活动与环境演变之间的关系研究很薄弱。本文通过对下大武遗址各粒级炭屑浓度的分析，试探讨其与人类活动和环境的关系。研究发现：（1）全新世大暖期时，气候温暖湿润，适宜生存。在对应的历史文化层中各粒级炭屑浓度出现高值区，说明此时下大武地区人类活动频繁，地方火和区域火频繁出现。（2）全新世中期，季风减弱，气候向冷干转变，植被退化，炭屑浓度普遍处于稳定的低值区，反映当时下大武地区人类活动的强度与范围缩小。（3）全新世晚期以来，3700--1800cal．aBP炭屑浓度出现明显高值区，指示高原区域火的发生；1800cal．aBP以来各粒级炭屑浓度波动频繁，粗粒炭屑浓度的波幅最大，指示下大武地区人类活动增强。

英文摘要：

Background, aim, and scope Fire as an unique and important ecological factor, both in past and present, has a significant impact on the environment. Charcoal is the direct product of fire and vegetation, it＇s related to both climatic changes and human activities. Therefore, charcoal not only can be used to reconstruct ancient fire event, but also indicate the strength of human activities. Xiadawu site which is located on Tibetan Plateau with 4000 meters elevation has been excavated in 2007. However, the research on the relationship between the ancient climate and human activities is rarely. In this paper, we analyzed the concentration of each granular level of charcoal in Xiadawu site, and attempted to explore its relationship with human activities and the environment changes. Materials and methods Soil samples were collected for determination of charcoal. Heavy liquid flotation was used to isolate the charcoal, and pollen circuit method was used to count the charcoal which was separated from soil samples. According to the long axis of charcoal, charcoal samples were separated for grading： 〈50 μn （fines）, 50-- 125 μm （medium grain） and 〉125μm （coarse）. Coarse-grained charcoal indicated local fire events, and fine-grained charcoal indicated region fire events with large area. Charcoal concentration reflected the intensity and frequency of the fire. Four charcoal samples were collected for radiocarbon dating. Results The results showed that： （1） The average concentration values of each grade showed obvious peak value during the Holocene Optimum Period and the Medieval Warm Period, fluctuated frequently. （2） The average concentration of fine-grained charcoal took a great proportion in the total concentration of charcoal, and the average concentration of coarse-grained charcoal was lowest. （3） In the whole profile, the average concentration of fine-grained charcoal reached maximum during 2200 cal.a BP. Discussion （1） During the Holocene Optimum Period, the climate was warm a