生态脆弱带的尺度与等级特征

Spatial Temporal Scale and Hierarchy of Vulnerable Ecotone

生态脆弱带（ＶｕｌｎｅｒａｂｌｅＥｃｏｔｏｎｅ）的物质、结构和能量流动特征依赖于主观所划分的空间域，脆弱带的空间尺度不同其特征也不尽相同，空间域的大小决定着所研究生态脆弱带的复杂性和稳定性。在一定的空间尺度下，脆弱带的组成要素随时间尺度的变化而变化，变化的速率依赖于空间尺度的大小，空间尺度越大，变化速率越小。除界面物理特征外，生态脆弱带的其它特性具有等级结构，空间尺度决定研究单元的等级位置，研究单元的尺度越大。

In this paper, the author reviewed the concept of the vulnerable ecotone in theoretical and practical aspects. The vulnerable ecotone has been defined a s special ecotone as it was more sensitively affected by environmental factors change and ecological processes fluctuation than the original concept of ecoton e. Thus, the characteristics of material, structure, and energy flows in the vul nerable ecotone close depend on spatial scales which are divided by researchers, because the spatial area determines the complexity and stability of the vulnera ble ecotone. For example, the agri animal husbandry ecotone in north China includes sever al provinces and more than a hundred counties, concerns different ecological, cl imatic and geographical systems. It is a large scale concept. Its universal cha racter is a vulnerable ecotone in which agriculture and animal husbandry regime interlaces each other, which is considered as a homogeneous region in this scal e. But if a small scale is used to analyze the above mentioned region, there ar e different geographical units that include Horqin, Erdos, and Bashang regions. They have same characteristics in comparison with the agri animal husba ndry ecotone of north China. The complexity and stability of agri animal husban dry ecotone of China are higher than that in Horqin region under same disturbanc e process. In addition, the composition elements (Holon) of the vulnerable ecotone vary from small area to big area in constant spatial scale, because agricultural and grazing regime and climatic change extremely affect ecotonal composition in dif ferent spatial and temporal scales. The large scale vulnerable ecotone has high er heterogeneity and buffer ability than small scales, so big vulnerable ecoto ne changes less than small in same disturbance regime. The variation rate of the element increases with the element area decrease, otherwise element composit ion complexity decreases with element area decrease. According to the above mention, it is considered that the vulnerable ecotone has hierarchical structure except its physical characters: the larger unit area is, the higher hierarchy is. So there are several key points which must be paid mor e attention to in future study concerning the vulnerable ecotone. First, how lar ge spatial and temporal scales will be used to analyze and describe the vulnerable ecotone, and what kinds hierarchical structure is it. Second, how to explain a nd manipulate the research results are very important for extrapolating and pred icting the traits of different spatial and temporal scales. Third, the change ra te of composition element studied in the paper can not be used over study scale, be cause the variation rate of composition element in the vulnerable ecotone depend s on scale.