Soil water content measurements (cm3 H2O / cm3 soil) at 5 depths at each of 89 (2" O.D. diameter) aluminum access tubes on the Control transect and at every 5th station on the nitrogen fertilized Treatment transect using a neutron probe (Campbell Model 503DR Hydroprobe). Access tubes are installed such that there are 6 inches of tube aboveground. Stations are 30 meters apart. Measurements are taken at 30cm, 60cm, 90cm, 110cm, and 130cm. Neutron probe readings taken in 6 lysimeters along transects are also included. 5 standard readings are taken at beginning and end of each transect, and after every 20 stations. Measurements taken at 2 week intervals from April 1982 to 1987, monthly since.

PO4-P levels in CaCl2 and NaHCO3 extracts of soils collected at each station along transect. Moisture content of soil samples is also included. No soil samples were collected along the fertilized (treated transect) in January 1985; January 1986 data contains both fertilized (treated) and control transect samples.

Total nitrogen in soil was determined on control and treatment (fertilized) transects by Kjeldahl digestion.

*We designed a study to examine the long-term spatial and temporal patterns of mass loss, changes in nitrogen content and chemical composition during decomposition of roots in a desert watershed. Because nitrogen availability has been hypothesized to affect decomposition rates of buried litter in deserts, we studied decomposition of roots along a transect on a desert watershed that had been fertilized with ammonium nitrate and compared these results with the decomposition of roots along a transect that had not been fertilized.

Soil nutrient distribution in NPP quads in the Mesquite, Grassland, Playa, Creosotebush, and Tarbush plant communities sampled at 3 spatial scales of grids. Soils were sampled from the NPP (biomass plots). Each of the five vegetation types (mesquite, grassland, playa, creosote, tarbush) had three sites (with low, medium, and high production levels). At 14 of 15 sites a grid of 70 by 70 meters was set out. Within this 49 plots of 10 by 10 meters were placed and labeled (numbered) in serpentine design. At the 15th site, Playa College, 48 plots of 10 by 10 meters were laid out in three long rows of 16 plots per row. At all sites the soil sample of 0-10 cm depth was taken 1 meter from the NE marker bar at a diagonal (heading toward the SW marker). 70m x 70m layout of NPP quads where 1 is in NE corner. 43 42 29 28 15 14 1 44 41 30 27 16 13 2 45 40 31 26 17 12 3 46 39 32 25 18 11 4 47 38 33 24 19 10 5 48 37 34 23 20 9 6 49 36 35 22 21 8 7 160m x 30m layout of P-COLL NPP quads where 1 is in NE corner. 33 32 1 34 31 2 35 30 3 36 29 4 37 28 5 38 27 6 39 26 7 40 25 8 41 24 9 42 23 10 43 22 11 44 21 12 45 20 13 46 19 14 47 18 15 48 17 16 At one of each of the five vegetation types another set of 49 soils (#101-149) was taken from within one of the 10 by 10 meter plots. Using a 7 by 7 meter grid (bounded by the southern east-west boundary line and the western north-south boundary line[#149 is in the SW corner]) soils were sampled 1 meter apart using a serpentine design. 7m x 7m layout within single 10m x 10m NPP plot. 143 142 129 128 115 114 101 144 141 130 127 116 113 102 145 140 131 126 117 112 103 146 139 132 125 118 111 104 147 138 133 124 119 110 105 148 137 134 123 120 109 106 149 136 135 122 121 108 107