城乡样带景观梯度分析的幅度效应

Extent effect of landscape gradient analysis of urban-rural transect

基于梯度分析与景观格局定量分析相结合的方法,通过改变样带宽度与研究步长,对城乡样带景观梯度分析的幅度效应进行了研究。结果表明:城乡样带景观梯度分析具有尺度依赖性,样带宽度对分析结果的影响大于研究步长;研究步长主要影响各景观指数沿样带波动的剧烈程度,将样带等分为20个样方时的研究步长是分析该样带梯度规律的适宜尺度;样带宽度存在"临界阈"现象,当样带宽度越过临界值时,各景观指数沿样带的梯度规律均发生变化。此外,不同景观指数对城乡样带景观梯度规律的反映存在差异,各景观类型的面积比例、边缘密度和景观Shannon多样性指数沿样带的梯度变化规律明显,而斑块密度和平均斑块分形维数沿样带的梯度变化规律不明显。

With the combination of gradient analysis and quantitative analysis of landscape pattern, and by changing the transect width and research step, the extent effect of landscape gradient analysis of an urban-rural transect were studied. The results showed that the landscape gradient analysis of the urban-rural transect was scale-dependent, and the effect of transect width was greater than that of research step. Research step mainly affected the fluctuation degree of each landscape index along transect, and it was appropriate for the transect to be divided equally into 20 samples. There existed critical values for transect width. When the transect width was beyond the values, the fluctuation trend of each index along transect would be varied. Furthermore, different landscape metrics responded differently to the same transect. The percent coverage and edge density of each class, as well as the Shannon＇ s diversity index of landscape, showed significant gradient characteristics, while patch density and mean patch fractal dimension were in adverse.