生态脆弱带内部空间分异结构与脆弱度划分

The Spatial Differentiation Structure and Weakness Assessment of Ecotone

内蒙乌盟后山及河北坝上地区是研究土地利用的人为驱动、气候驱动同全球变化关系的理想剖面。区内气候风蚀力代表了自然地理条件的主分异方向 ,其值在 70～ 3之间 ,高低差别很大。区内 4 2 a内单位面积上牲畜头数累积减少量以旱作界线附近为最高 ,向南北两侧减低 ,且南部高于北部。 2 0世纪 80年代沙漠化的发展并没改变本世纪 70年代沙漠化程度分布的基本格局。两个时代具有相同的空间分布规律 :沿旱作农业北界附近的旗县为沙漠化最严重的地带 ,向南部坝上农业地带和北部牧业地带递减。虽然社会经济因素仍以西北东南为分异的主方向 ,但滥垦加剧了农牧交错带梯度分异 ,旱作界线附近构成了社会经济因子分异的跃变地带。对区内 2 0个旗县 1 3个因子的旋转主成分分析表明 ,前 4个主成分约分别为 33%、2 1 %、1 5 %和 1 4 % ,各自代表社会经济条件、灾害、气候风蚀力和沙尘天气四类要素。根据其分异规律 ,自东南向西北可将本区划为南部农牧中度脆弱、中部牧农重度脆弱和北部牧业轻度脆弱 3个弧形地带。

Area of upland and rear hill is situated in the southeast Inner-Mongolia plateau between Hebei Province and Inner-Mongolia autonomous region. Nowadays, there are here great population pressure on land, heavy erosion of water and wind, rapid desertification expansion and high fluctuation of eco-social compound system, all which lead to low living standard of local residents. As a result, the area becomes the most fragile part of ecotone in north China. Because of its peculiarity in eco-geography and major factor in global environmental change, the area also become the core region of NECT in IGBP, which are intended to discuss the relation between global change and land use driven by human and climate. In the paper, taking the area of upland and rear hill as typical section, which stretches 500 km long and 300 km wide and deals with 18 counties and banners, to be discussed is the spatial differentiation of ecotone elements such as climatic erosion force, losses in animal husbandry, desertification status and economic level, from which the major differentiation factors are chosen based on the method of PCA, then the weakness degree of the whole region be assessed. Climatic erosion force is not only the integration of meteorological factors such as wind, precipitation and temperature, but a driving force of desertification and dust storm. So it can represent eco-geography differentiation. According to the principle about C′of Chepil and FAO, the author puts forward a new equation for the wind erosion force (C′):C′=U\+3S -2 S=∑12i=1S\-i S\-i=0.18P/1.045\+t In keeping with the results of Bailer's humidity index S, we can have an objective reflection of regional humidity situation with the meteorological data from 1960～1980. 2.5 isoline of Bailer's distributes in the same way as that of 200 mm of precipitation, 4.5 the same as 400 mm, most of the region range from 4.5~2.5. Average C′of many years in this area is between 70~3 and decreases from Erenhot to the south which reflects the principal differentiation direction of eco-geography. In agreement with the conversion of standard sheep unit, which is 1 sheep for 1 sheep unit, 1 draught animal for 4.5 sheep unit, using the original number of livestock for end of year from 1951~1992, the paper establishes a new serial of livestock through the value of this year minus last year. Though factors like natural disasters, policies and market contribute greatly to the decrease of livestock, the new serial of livestock can approximately represent the influence of disasters. The highest accumulated number of livestock which decreased from 1951~1992 are in the counties along dry farming line from which it decreases toward two sides with the south a little higher than the north. Making use of the remote sensibly monitoring of the mid 1970s and 1980s, the sandy desertification status and spatial differentiation in the area is discussed. Overall degradation status of the region is 2.8% in the mid 1970s and it increased to 5.8% in the mid 1980s. There is a tendency of degradation status from the mid 1970s to the mid 1980s for aggravation of the total situation. The desertification development in 1980s didn't change the basic structure of which in 1970s, both are of the same distribution pattern: desertification status is the highest along dry farming line and decreases toward two sides. Furthermore, the most severely desertified type always distribute along the dry farming belt during 1970s^1980s. It went separately in the 1970s and occurred only in Siziwangqi, Darhan Mumingqi, Zhenglanqi, Fengning and Duolun. After newly emerged in Huade, Shangdu, Qahar Youyi Zhongqi,Wuchuan and Baiqi, they linked together from west to east forming an axis of severity degree with the length of 700 km in the 1980's. In addition the gradient change in unit area for yield of calorie and protein is analyzed. Meat yield is corpus and net meat ratio is 80%. General food structure and nutrition component of China is taken as conversion criteria. As