The Environmental Change And The Evolution Of Human-earth Relationship During Holocene In Tianshui Area

Three Holocene loess-palaeosol profiles in Tianshui area were studied by field investigation, intensive sampling and laboratory analysis, including Grain-size (GZ) analysis and measurement of magnetic susceptibility (MS). GZ and MS, used as a proxy indicator of East Asia winter monsoon and a proxy indicator of summer monsoon respectively, together indicate that the climatic environment of Holocene in Tianshui area can be divided into three main stages: first Anathermal, then Magathermal, and last Katathermal, and during the middle Magathermal period, a cold and arid event occurred in the studied area. Meanwhile, based on the climate history, the author also analyzed the evolution of human-earth relationship during the last ca. 10000 years with the help of archaeological studies documents and historical records.The main results in this study are following:(1) Anathermal (11500-8500 a B. P.)Summer monsoon got stronger and stronger, that its intensity closed to or even exceeded what of winter monsoon. As a result, the climate came to get warm and moist in Tianshui area. However, the sharply climatic incidents during this period could cause serious calamity and would be disadvantageous to living beings' multiplication and human development. Our forefathers still lived a without definite residence life by gathering and hunting. The human-earth relationship was still in an inevitable state at this stage.(2) Magathermal (8500-3100 a B. P.)Summer monsoon occupied the dominant position for a long time, and the weather was warm and moist in our studied area as a whole, nevertheless the climate was not always stable.8500-6000 a B. P., summer monsoon reached its maximum and the climatereached its optimum phase of Magathermal. With this kind of advantageous natural environment, Dadiwan culture came into being and developed rapidly.6000-5000 a B. P., a climatic deterioration incident had taken place in lots of areas besides Tianshui area. But then the deterioration was not so severe in Tianshui area that human activity was still going on. On the other hand, change of environment could compel human beings to adapt to and remodel the environment, to develop technology, consequently to promote the development of human civilization, such as Dadiwan culture.5000-3100 a B. P., it got warmer and wetter again. Changshan culture developed. Our forefathers still lived settling-down life and made use of lots of potteries.(3) Katathermal (Since 3100 a B. P. )At this stage, winter monsoon got strong and climatic deterioration occurred again. Tianshui area entered into a relatively dry and rain shortage period. Nomadic industry and stockbreeding increased in Shiwa and Western Zhou cultures.(4) Average annual temperature and precipitation take on a trend of decreasing gradually from southeast to northwest, which proves the fact that summer monsoon has the trend of increasing from northwest to southeast. Accordingly, under the double influence of global change and regional climate, the southeastern part was obvious warmer and moister than the northwestern part in the studied area in Holocene.(5) The modern ecological environment deterioration of Tianshui area is the result of double actions of climatic deterioration and artificial factors in the past. Thus, in the present construction of eco-environment, it is the first-selected way that we human beings work all out to coordinate the human-earth relationship scientifically, protect the natural vegetation, concede the land to forestry and grass and increase the area covered with vegetations to contain degradations of water and soil resources.