Key points are not available for this paper at this time.
The U.S. Department of Agriculture Agricultural Research Service Southwest Watershed Research Center Walnut Gulch Experimental Watershed (WGEW) is an outdoor laboratory located in southeastern Arizona to study water and soil conservation in semiarid lands. Permanent vegetation transects were established adjacent to 55 rain gauges within WGEW in 1967 to quantify vegetation. Some sites were subsequently added or dropped. Detailed vegetation data were collected in 1967, 1994–2000, and 2005, including repeat photography of transects. Ground cover data were collected after 1967. A vegetation map was developed in 2002. The transect sites, vegetation map, data collection methods, and current data availability are described. Data are available at http://www.tucson.ars.ag.gov/dap/ .
Skirvin et al. (2008) studied this question.