| In recent years, all too often it seems as though our pursuit of economic security or improved station in life leads us to compromise or even undermine the quality of the natural environment, further, strengthen the conflict of human and nature. Until recently, however, people have realized that our future and well-being depending on the normal and functional earth system, thus, deepen studies and comprehensive insight of the human-earth interaction is in sore need.The Jianghan Plain, suited in Central China, is a typical floodplain of the middle Yangtze and the Hanjiang River composed of many interchannel depressions, with a variety of complicated geological factors, including sedimentary provenance, hydrodynamic conditions, microrelief of rivers and lakes, climate, and sedimentary environment. Its main body is located in the transitional zone of the second to third step of the so-called "three-step ladders" Chinese topography, therefore, a unique spatial location. Controlled by the East Asia monsoonal climate, both temperature and precipitation of the plain exhibit remarkable seasonal variability. As important national commodity grain production base, key industry construction area and irreplaceable transportation junction, the Jianghan Plain is now experiencing high speed economic-social modernization while, consciously or unconsciously, strengthening more and more pressure on the environment and ecosystem which have severely affect the regional sustainable development. Archaeological research has demonstrated that as far back as the Palaeolithic Age humans had been thriving here. Around5300years ago, Qujialing Culture whose core area was in the north-central of the Jianghan Plain broken the southern system and northern system parallel pattern and unified the Neolithic Culture in the middle reaches of the Yangtze Rivers. This marks the beginning of the early civilization in China from the prehistoric culture, unfortunately, dramatically declined in the late period of Shijiahe Culture and following with the Post-Shijiahe Culture a prehistoric culture hiatus of hundreds of years long in the Jianghan plain. Hence, the Jianghan Plain is a typical area to depict the global to regional-scale natural system changes and long-term regional to local scale human-earth interactions. On the basis of investigation and studies of the tectonic and geomorphologic conditions, this paper reconstructs the geographic environment changes during5.5-3.4kyr BP using multi-proxies synthesis integrating method. Meanwhile, the spatial-temporal pattern of changes of the different cultural periods, along with the transformations of the typical prehistoric settlements, were analyzed and compared by means of GIS or spatial analysis. Further, this study discuss the mechanism of the geographic environment changes and the relationships between the archaeological culture evolutions and the geographic environment changes, ultimately, solving the key scientific question which is the structure of the regional man-earth system of the Jianghan Plan, as well as how the system components and elements are dynamically related in different spatial-temporal process during5.5-3.4kyr BP.Based on the time sequence of the JZ-2010profile derived from AMS14C dating and the comprehensive analyses of the multiple alternative environmental indicators, such as the spore-pollen assembles, the TOC, TN,δ13Corg values, the geochemical components, the magnetic susceptibility and the granularity parameters, combining geomorphic conditions and sedimentary features, the palaeoenvironment of the Jianghan Plain during5.5-3.4kyr BP was generally warm and humid, however, with enhancing instability and the trend of drier and colder. Over the time, the lakes expanded with a low deposition rate as the result of very little sediments were brought into the basin by surface runoff, consequently formed clayey silt. The vegetation distribution was mainly the subtropical evergreen needleleaf-broadleaf and mixed forest and woodland. All the environmental indicators recorded severe drought during approximately4.4-4.2kyr BP, apparently responding the4.2kyr event. The integrated of the JZ-2010records, the results of typical archaeological rectangular units, as well as the selected previous research works demonstrated five stages of the climate and environmental changes of the Jianghan Plain from5.5to3.4kyr BP: unstable warm-wet stage (5.5-5.1kyr BP) in the period of post Holocene Thermal Maximum, appropriate warm-humid stage (5.1-4.5kyr BP), warm and dry stage (4.5-4.2kyr BP), slightly warm and wet-dry seesawing stage (4.2-3.7kyr BP), stable but weaken warm-humid stage (3.7-3.4kyr BP). Moreover, two high frequency flood periods events are manifested during4.9-4.6kyr BP and4.1-3.8kyr BP.Comparative analyses revealed that the impacts of regional topography that sustained tectonic subsidence since the Cretaceous, adding its southeast tilt, a dustpan-shape surrounded by mountains in the west, northwest and north, opened the Jianghan Plain to the summer monsoon, has resulted distinctive environment changes and regional responses to the global changes since the mid-Holocene.Archaeological studies have identified the Neolithic cultural sequence in the Jianghan Plain during5.5-3.4kyr BP which consist of Daxi Culture (6.5-5.1kyr BP)/Youziling Culture (5.9-5.1kyr BP), Qujialing Culture (5.1-4.5kyr BP) and Shijiahe Culture (4.5-4.0kyr BP). Using GIS combined with archaeological and geographic data, this dissertation presented that most of the related Neolithic sites are concentrated in the western and northern edge zone, with an altitude of30-100m, on the lower terraces of rivers and piedmont downlands, demonstrating the significant effects of the regional tectonic features, as well as the landform featured with latitude decreasing from edge to centre. Owing to its geographic locality and complexity, the Jianghan Plain showed pretty well climate conditions and ecological advantages that witness the development of the Daxi-Youziling Culture. After5.3kyr BP, the rapid expansion of the Youziling and the following the Qujialing’s unity of the prehistoric culture in the middle reaches of the Yangtze were attributed to its unique geographic location of the eastern area of Hanjiang River (the Handong Area). Comparing with the other areas in the Jianghan Plain, the Handong Area possesses stronger accessibility, lager land with rivers and lakes, more abundant natural recourse, all combining made the Dahong Mount piedmont downland an ideal habitat for prehistoric human being.Discussion on the climatic and environmental changes and Neolithic Cultures evolutions in the Jianghan Plain during5.5-3.4kyr BP revealed their dynamic correlation. Continuous appropriate warm-humid climate and well ecologic environment promoted the flourishing of the Qujialing Culture, however, increasing population and expanding settlement scale gradually enhanced the pressure on the regional environment and resources. From approximately4.5kyr BP, the environmental recession and resources limited urged a more tighten primitive society structure and highly organization, objectively pushing the development of the Shijiahe Culture. The virtuous interaction of human and nature was broken by the4.2kyr event whose severe drought and following floods eroded the economic foundation on the basis of rice-cultivation agriculture, the Shijiahe Culture dramatically withered and left a culture hiatus. The dynamic interrelation of the Jianghan Plain human-earth system in different spatial-temporal process over the5.5-3.4kyr BP could be summarized as three types:harmonious growing type, conflicting fragile type and critical destructive type, which was corresponding to the archaeological cultures flourishing, shrinking and died out at last. |
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