Abstract:Scale issue is fundamental to all ecological investigations, and has become a central topic in ecology in recent decades with rapid development of digital technologies (remote sensing, GIS, etc.) and emergence of landscape ecology. Landscape indices are widely used in the study of landscape pattern change to describe landscape components and spatial distribution. Most of analyses on landscape pattern are based on grid data, which are always converted from vector data. In this data conversion process, scaling and the methods of scaling used are critical. Many researchers have studied the effects of different landscape indices, but most of these indices are calculated from algorithm among patch area, patch perimeter and patch numbers, and there are few studies about how to choose the suitable scales and methods for determining patch area, patch perimeter and patch numbers in the conversion from vector data to grid data.
This paper presents changes of patch area, patch perimeter and patch numbers under the different conversion methods and scales. It took landscape map of KuBuQi desert as an example, which was extracted by the interactive method between operators and GIS (geographic information system) software ArcView3.2. It analyzed the effect by using conversion methods, including the Rule of Maximum Area (RMA) and the Rule of Centric Cell (RCC), and conversion scale, which changed from 10 m to 200 m on the 10 m scale. And it also analyzed the time effect of calculation with different conversion methods and under Fragastats3.3 software.
The results show that the patch area, patch perimeter, patch numbers and calculation time have obvious scale-effect with conversion methods and scales changing. In the end, it concluded that based on the landscape map at the 1∶100000 scale, the appropriate scale for landscape index was 30 m, and the appropriate conversion method was the Rule of Maximum Area (RMA). The conclusions have implications for studying similar landscape regions in desert areas and for an improvement of the scale conversion method in landscape ecology.