QUANTIFYING LANDSCAPE SPATIAL PATTERN - WHAT IS THE STATE-OF-THE-ART

Landscape ecology is based on the premise that there are strong links between ecological pattern and ecological function and process. Ecolog ical systems are spatially heterogeneous, exhibiting considerable comp lexity and variability in time and space. This variability is typicall y represented by categorical maps or by a collection of samples taken at specific spatial locations (point data). Categorical maps quantize variability by identifying patches that are relatively homogeneous and that exhibit a relatively abrupt transition to adjacent areas. Altern atively, point-data analysis (geostatistics) assumes that the system p roperty is spatially continuous, making fewer assumptions about the na ture of spatial structure. Each data model provides capabilities that the other does not, and they should be considered complementary. Altho ugh the concept of patches is intuitive and consistent with much of ec ological theory, point-data analysis can answer two of the most critic al questions in spatial pattern analysis: what is the appropriate scal e to conduct the analysis, and what is the nature of the spatial struc ture? I review the techniques to evaluate categorical maps and spatial point data, and make observations about the interpretation of spatial pattern indices and the appropriate application of the techniques. Pa ttern analysis techniques are most useful when applied and interpreted in the context of the organism(s) and ecological processes of interes t, and at appropriate scales, although some may be useful as coarse-fi lter indicators of ecosystem function. I suggest several important nee ds for future research, including continued investigation of scaling i ssues, development of indices that measure specific components of spat ial pattern, and efforts to make point-data analysis more compatible w ith ecological theory.