The development of poleders in the lower reaches of yangtzi river and their influence on the ecological environment 长江下游圩田开发及其对生态环境的影响
2.
During the northern and southern song dynasties , the tapping of the enclosed lands has been developed quickly in the lower reaches of the yangtze river 摘要两宋时期，长江下游地区圩田开发在以往的基础上进一步迅速发展。
3.
In the process of tapping and using these enclosed lands , a series of aquatic disputes arises due to vicious factors such as fighting for more water supply , draining of flooded fields , scrambling for more areas and intended destroying lakes and rivers 人们在圩田开发利用过程中，因为争水、排涝、抢占河湖滩地，以及对陂湖的恣意破坏等因素，产生了诸多水事纠纷。
4.
Then , with the help of gis , i selected 8 soil fertility factors mentioned above and soil texture as parameters , used blocks generated by overlaying each factor theme as assessing unit , modified nemoro fomular , and then i assessed the overall soil fertility quality of wujin city , we know : the soil fertility quality of the city is generally medium or worse , in it , the district of riverine polder the district of menghe even fields the district of taige even fields and the district of hilly lands are on " worse " level , and the district of zhengheng polder the district of lakeside polder and the district of taoge even fields are on " medium " or " better " level 接着在gis支持下，选取以上8项土壤肥力要素并加上土壤质地作为参数，以各要素图层叠加产生的图斑作为评价单元，修改内梅罗公式，对武进市土壤肥力质量进行综合评价，得出：土壤肥力质量中等偏下，其中，沿江圩田区、孟河平田区、太涌平田区和低山丘陵区主要处于“较差”水平，而郑横圩田区、沿湖圩田区、洮?平田区主要处于“中等”及“良”水平。
