概述

位于中国东部，包括第一阶绨的全部和除内蒙古地区以外的第二阶梯大部.约占全国陆地总面积的４７６％，占全国人口的９５％，占耕地面积的９０％以上.这一B区域受东亚季风及西南季风的影响形成季风进退极为明显活跃的典型季风气候.（１）夏季海洋季风影响显著，自３月上旬夏季风逐步北进、西进，７月中旬达到极盛，北及于第二阶梯的西北部边缘部分.同时印度洋西南季风自６月上旬以突发形式大规模北进，经青藏高原东部边缘影响云贵高原及华南沿海，特殊情况下可波及到北纬３０°左右地区.８月底到９月初夏季风南撤，冬季风于此时南进，于９月底１０月初到达华南，以较快速度影响到全国，冬季风南界可达南海，西界达青藏高原东缘.从而使全区风向及降水量随季节面有明显的变化和有规律的更替.（２）在南北狭长的范围内，自然界的分异受纬度及相应的气温控制.在北部，湿润程度受距海里程的增加而减少.天然植被以森林为主，有部分地区为森林草原.（３）新构造上升幅度不大，超过２００米的山岭不多，绝大部分地区在海拔１００米以下.在钦州—郑州—北京—齐齐哈尔一线以东地区以沉降为主，海拔更在５００米以下，为中国主要农业区及大工业区所在地.全无现代冰川.（４）地貌外营力以侵蚀、堆积及溶蚀作用为主.地表水以雨水为主要补给来源.潜水有相当数量.（５）由于第四纪冰期没有强大的冰川作用，动植物区系未受到损害，因而生物种类繁多，土壤及疏松的堆积物也未遭受破坏.（６）人口密集，开发历史悠久，大部农田已开垦，天然森林已不复存在，无真正的原始森林.环境问题较突出.根据纬度及温度可以划分为寒温带、中温带、暖温带、北亚热带、中亚热带、南亚热带、边缘热带、中热带及赤道热带九个自然带，而以暖温带及北亚热带面积最辽阔.边缘热带即不典型的北热带，中热带及赤道热带涉及陆地面积较小，仅五指山以南的海南岛及南海诸岛.云南高原作为低纬度高原应属青藏高原东部，因海拔较高（昆明平原面１８０—２２０米，中甸平原面３１００米），在纬度上虽属中亚热带，但高于１０℃的年积温仅达４５０°—５５０℃，比东部地区低近一半，也以划入青藏高原区为宜.但因高原上多红壤（尽管与东部红壤在性状上有明显差异），且并非高寒气候，可暂按习惯划入东部季风区域.在土壤分布上以秦岭—大别山为界，以南土壤质地粘重，多呈酸性反映，以北土壤富含石灰质，呈碱性反应.东北地区土壤有机质丰富，东北东部呈酸性反应，东北西部则含石灰质.在北方及西北部低洼地盐分积累明显，有时可成盐渍土.东部季风区域可初步划分为东北北部湿润半湿润寒温带地区、东北湿润半湿润中温带地区、华北湿润半湿润暖温带地区、华中华南湿润亚热带地区和华南热带温润地区５个地区，１９个区、７１个亚区.东北北部湿润半湿润寒温带地区Is located in eastern China, including the first-order ti all and in addition to outside the region of Inner Mongolia most of the second ladder. About the country's total land area of 476%, accounting for 95% of the country's population, accounting for more than 90% of arable land. This B region affected by the East Asian monsoon and the southwest monsoon affecting the formation of an active monsoon retreat highly visible typical monsoon climate. (1) the summer monsoon significantly affected, since the beginning of the summer monsoon in March and gradually northward and westward, and reached its apogee in mid-July, the North and at the north-west edge of the second part of the ladder. At the same time since the Indian Ocean southwest monsoon in early June in order to sudden large scale north through the eastern edge of Qinghai-Xizang Plateau affect the Yunnan-Guizhou Plateau and southern China coast, in special circumstances can be spread to north latitude 30 ° .8 around the region at the end of the summer monsoon Nanche early September, the winter winds south at this time, at the end of September early October to reach southern China, a more rapid pace affect the whole country, the winter winds can reach the southern boundary of the South China Sea, the West sector over the Xizang Plateau the eastern edge. so that the wind direction and precipitation in the region face significant seasonal changes and regular turnover. (2) In the context of long and narrow, natural differentiation by the latitude and the corresponding temperature control. In the north, humid miles away from the sea is affected by the increases. the natural vegetation of forest-based, there are some areas of forest and grassland. (3) new construction rise little more than 200 meters of the few mountains, most of the region at an altitude of 100 meters the following. In the Qinzhou - Zhengzhou - Beijing - Qiqihar line east of the main areas to settlement, even at 500 meters above sea level, in order to China's major agricultural areas and large industrial zone is located. no modern glaciers. (4) landscape outside the camp equipped to erosion, accumulation, and dissolution interaction. surface water with rainwater as the main supply source. a considerable number of divers. (5) Since the Quaternary Ice Age glaciers without a strong role of the flora and fauna are not damaged, and therefore species there the accumulation of soil and loose material has not destroyed. (6), population density, has a long history, most of the farmland has been reclaimed, natural forests have ceased to exist, no real native forests. prominent environmental problems. according to latitude and temperature can be classified as boreal, in temperate, warm temperate, subtropical north, the subtropical, subtropical south, the edge of the tropics, in tropical and equatorial tropics nine natural zones, but in order to warm temperate and northern subtropical area of the most vast. the edge of the tropical that is not typical of northern tropics and the tropical and equatorial tropics involves a smaller land area, just south of Hainan Island and the South China Sea Fingers islands. Yunnan Plateau as a low-latitude plateau should be the eastern Qinghai-Xizang Plateau, due to the higher altitude (Kunming plain surface 180-220 m , Zhongdian plain surface 3100 meters), the corporations are in the subtropical latitude, but higher than the annual accumulated temperature of 10 ℃ to only 450 ° -550 ℃, lower than in nearly half of the eastern region, also assigned to Qinghai-Xizang Plateau is appropriate. but more red soil plateau (although with the eastern red soil have significant differences in the characters), and is not a cold climate, can be assigned to the eastern monsoon region Zanan habits. in the soil distribution in Qinling - Dabie Mountains as the boundary, south of the sticky soil texture weight, Duocheng acid reflects the north is rich in calcareous soil, showing alkaline reaction. northeastern region of soil organic matter is rich in acidic reaction to the east north-east, north-east while the western region with calcareous. in the north and northwest of the low-lying land salt accumulation obvious, sometimes into a saline soil. the eastern monsoon region may initially be divided into the north northeast cold temperate semi-humid and humid regions, the Northeast in the temperate semi-humid and humid regions, semi-humid and humid warm temperate regions of North China, central South humid sub-tropical areas and southern regions of tropical moist region 5 , 19 districts, 71 sub-regions. northeastern semi-humid and humid in northern cold temperate regions