From Ecology Letters:

Although scaling relationships that characterize fractal species distributions offer an exciting potential for unification in biogeography, empirical support for fractal theory remains the subject of debate. We synthesize and test multiple predictions of two interrelated fractal models and a null model of random placement using Californian serpentine grassland data describing the spatial location of over 37 000 individually identified plants. The endemics–area relationship and species‐abundance distribution recently derived from a community‐level fractal property performed poorly because of an inaccurate assumption of homogeneity among species. In contrast, a species‐level fractal model that incorporates species‐level differences predicted abundances well, but systematically overestimated endemism and predicted a species–area relationship that violated the observed power law. These findings indicate that in order to make predictions based on the existence of a power‐law species–area relationship, ecologists need a unifying theory of how the community‐level fractal property arises in the presence of species‐level distributional differences.

This data is from a census carried out over the spring and summer of 1998 by Jessica Green on a 64 m^2 plot at the University of California’s McLaughlin Reserve in Yolo county, CA. The plot was gridded to a smallest cell size of ¼ m^2 and in each cell the abundance of every plant species found there was recorded. See paper for more information.

The spreadsheet (Serpentine.csv) provided here is organized as follows: the columns are plant species, with each species given a code name that is explained in Serpentine_SpeciesList.txt. There are 256 rows of data, with each row corresponding to one of the ¼ m^2 cells. If the plot is viewed as a matrix, then the first row of data in the spreadsheet corresponds to the upper left cell (matrix element a1,1). The second row of data is the matrix element a1,2, or in other words the cell just to the right of a1,1. The 17th row of data then corresponds to the plot matrix element a2,1, and the very last row of data is the lower right cell, a16,16. The actual data entries are the abundances of the species in each cell.

The data may be used by readers for any purpose, but any publication that includes use of the data should reference the data set to:

Green J., J. Harte, and A. Ostling, 2003. Species richness, endemism, and abundance patterns: tests of two fractal models in a serpentine grassland. Ecology Letters 6 919-928.

Moreover, the Acknowledgments should include a thanks to Jessica Green for use of the data.