The entire study area is approximately 20 ha and within this area there are 24 experimental plots (Fig 1). Each plot is 0.25 ha (50m x 50m) and fenced with hardware cloth topped with aluminum flashing. Access to these plots by rodents is regulated by gates cut into fencing. On each plot there are permanent census grids: one for rodents and ants and another for plants. For the rodent/ant grid, 49 permanent trapping stations are marked by rebar stakes forming a 7x7 grid, with 6.25 m between stakes. Every stake on a plot has a unique identifying number denoting the coordinate of that stake on that plot. For example, stake 11 is the first stake on the first row. Rows are numbered 1 through 7 going from the most northern row to the most southern. Columns are numbered 1 through 7 going from the most western column to the most eastern (Fig 1). The plant grid contains fewer rows and columns (4 rows, 4 columns). Numbering of the plant stakes follows similar rules to the rodent/ant grid, except that even numbered rows and columns are skipped (censuses use rows 1,3,5,7 and columns 1,3,5,7). Each plant quadrat is 1 m south of the rodent/ant stake of the corresponding number. Details for how these grids are used for data collection can be found in the metadata for the specific dataset files.
The site occurs on lands managed by the U.S. Bureau of Land Management. This region has been grazed by cattle since at least the late 19th century. In 1977, a cattle fence was erected around the study area to exclude cattle and no grazing has occurred on the 20 ha since that time.
There are two rainy seasons at the site, occurring roughly from Oct-April and July-Sept. Typically 60% of the annual rainfall occurs in the summer (Brown and Ernest 2002). The two rainy seasons result in generally two distinct annual plant communities, with a few bi-seasonal annual species.