Spatial scale analysis of the diversities of urban landscape: A case study within the external circle highway of Shanghai City

Landscape ecology is simply the study of relationship between spatial pattern and ecological processes over a range of spatial scales. Because of the scale multiplicity in spatial pattern and ecological processes, scale holds the key to understanding the pattern-process interactions and, indeed, becomes one of the corner-stone concepts in landscape ecology. Due to the limitation of theories and methods, in-depth studies on scales in landscape ecology have been limited, especially, for the studies on variance character and effect of the synthesis index of landscape pattern at different extents. The emergence of Geographic Information System and Remote sensing technologies provide an effective tool to characterize the spatial pattern and spatial heterogeneity at different extents. As an example, these techniques are applied to analyze the urban landscape diversity on the SPOT images at three extents. Firstly, this paper creates spatial pattern maps of landscape diversity at three extents; then it models the semivariogram of landscape diversity at different extents. The results of analysis indicate: (1) With the increasing spatial scale, the landscape diversity increases and the spatial pattern of landscape varies dramatically. At the 0.5km extent, the maximum of diversity is in the center of the urban. The landscape diversity distributes with a ring mode wavily from the center to the outer. With the increasing extent, the maximum of diversity moves to an urban-rural ecotone where landscape types change dramatically. At the smaller scale, the more details are to be detected. When scale increases, the local details fade out gradually while the character of whole spatial pattern stands out. Due to the development and the directions of its extending, landscape diversity is uneven as a whole. The coarser the scale is, the more obvious imbalance it shows. (2) The changes of spatial pattern of landscape diversity at different scales are closely linked to the characters and functions of urban landscape, especially to economic benefit, social benefit and cost. Due to the high spatial cost in the center of the urban, only the landscape types that have more social and economic benefits can be located. And thus, they have the characters of simplex type, high congregation and high fragmentation. While those landscape types of low economic and social benefits can only be located at the fringe or outskirt of the urban, they have the characters of simplex landscape types, larger patches and less fragmentation. However, the urban-rural ecotone has more various landscape types and complex pattern. (3) Semivariogram discloses the spatial variance character and internal mechanism of landscape diversity quantificationally. At a small scale, the spatial variance of diversity is more complicated. The spatial heterogeneity, which is caused by spatial autocorrelation, contributes a lot to the total spatial heterogeneity of terrestrial ecosystem, while the spatial heterogeneity which is caused by random factors (scale and measure error) contributes less. The increasing scale washes off the detailed variances in a fine scale. The coarse scale may results in more nugget effect and less contribution, which is caused by spatial autocorrelation. (4) Landscape diversity has the character of scale dependency, i. e. it is a function of scale. The results differ at different scales we have chosen, so influence of scales on pattern in the research of landscape ecology cannot be neglected.