中国北方农牧交错带生态环境脆弱性及其成因分析

ECOLOGICALLY VULNERABLE CHARACTERISTICS OF THE FARMING PASTORAL ZIGZAG ZONE IN NORTHERN CHINA

脆弱生态环境单元的两个特征是：环境敏感性和退化趋势。脆弱生态环境的研究不仅具有理论意义，而且有相当重要的实践价值。北方农牧交错带北起大兴安岭两麓向西南延伸，经内蒙古东南、冀北、晋北、直至陕北、鄂尔多斯高原、该地带的地质地貌、气候、生物、土壤等自然条件和人文要素，尤其是土地利用方面，都表现出过渡性和波动性特点。这种过渡性和波动性，在一定程度上决定了人类活动方式的不稳定性，进而导致该区域生态环境经常受到冲击和破坏，而将潜在的自然环境脆弱性转化为现实的破坏。因而农牧交错带生态环境表现出敏感性强、退化趋势明显等脆弱特征。本文在综合分析农牧交错带自然条件的基础上，概括出导致该地带生态环境脆弱的四大因素：一、脆弱的地表物质基础和土体构型；二、降水时间分配不均，多暴雨，利用率不高，且为害严重；三、干旱多风，侵蚀强烈，恶化了生态条件；四、不合理的人为活动干扰和破坏。

Ecologically vulnerable environment, which is made up of vaious categories and hassophiscated catises,is a kind of sensitive environment with degradation trendence,Thestudy on it is very important for us to maintain ecological balance and conserve natural en-vironment. The farming pastoral zigzag zone in northern China begins from Hulunbeier Stepps in Neimenggo Autonomy Region,extending south westernly,through the south east ofNeimenggo Autonomy Region,north of Hebei and Shanxi provinces, straightly to theLoess Plateau of northern Shaanxi and Eerdosi Plateau,which is characterized by transitionand vibration with either the natural condition or the human activities. These ,to some ex-tent,result in instablity of the model of huamn activities ,and make eco-environment in this region bit and spoiled.As a result , the potential vulnerability is transformed into prac-tical spoilage . So ,the eco-environment in the farming -pastoral in northern China is withtwo characteristics : strong sensitivity and explicit degradation trendence,。The factorscausing the vulnerability in the farming-pastoral zigzag zone are follows:(1)vulnerablesurface material formation,(2)unevenly-distributed precipitation in time and space, andaccordingly,frequent flooding and drought disasters,(3)strong wind ,and,(4)irrationablehuman activities.