Landscape ‘Contagion’ in Raster and Vector Environments

Abstract

Abstract Raster land cover data has been used to construct adjacency matrices by scanning the pixel edges and calculating proportions according to the land cover types joined. Like joins (e.g., forest to forest) are most common because pixel size is typically much smaller than the average patch size. The dominance of like joins (the matrix diagonal) of the adjacency matrix has led to one interpretation of the matrix as landscape contagion (the tendency of land cover to cluster into a few, large patches). Construction of the adjacency matrix in a vector environment results in a different measurement. In a vector environment, land cover patches are not sub–divided into pixels. Therefore, the main diagonal of the adjacency matrix is zero. Construction of an adjacency matrix in a vector environment estimates the evenness of distribution of edge types, not contagion. The same edge type evenness metric is estimated in a raster environment by ignoring the matrix diagonal and re-scaling the off-diagonal elements so that they sum to one (1).