Four mesquite ecosystems were studied: playa, coppice dune, arroyo (or wash), and grassland. An ecosystem dominated by the non-legume, Larrea tridentata, and lacking mesquite was included as a reference. At four shrubs on each site, samples were taken from two depths (0-15cm, 15-30cm) and three canopy positions: base, mid-canopy, canopy edge. An interzone area was also sampled at both depths. The soils were analyzed for Total Kjeldahl Nitrogen (TKN), inorganic N-- nitrate-N, and ammonium-N. This study was conducted in 1986 and is complete.