Data set ID:
Ammonia volatilization was measured at three sites in the Chihuahuan Desert of southern New Mexico, U.S.A. In dry soils, ammonia volatilization ranged from 9 to 11 micrograms of nitrogen per square meter per day, but rates increased to 95 micrograms of nitrogen per square meter per day in a shrubland site after an experimental addition of water. Ammonia volatilization also increased with experimental additions of NH4Cl and decreased with additions of sucrose. Competition by nitrifiers for available NH4+ had little effect on NH3 volatilization: N-Serve, added to inhibit nitrification, decreased NH3 volatilization in a grassland site and had little effect at other sites. We suggest that NH3 volatilization is controlled by the rate of mineralization of NH4+ from soil organic matter, and mineralization is stimulated by rainfall. Overall rates of NH3 volatilization from undisturbed desert ecosystems appear to be much lower than those reported for rangeland and agricultural soils.
The data set shows ammonia volatilization from grassland, cresotebush, and playa habitats in response to a variety of experimental treatments chosen to elucidate the processes controlling the volatilization under dry and post-rainfall conditions. Ammonia is collected in weak acid in scintillation vials placed inside PVC chambers in the field. The rate of ammonia volatilized per unit area ugN/m2/day) is found by mulitplying the concentration in the acid by 1250 to account for volume and area corrections.
Methods of recording (field data sheets, instrumental, etc.):
Methodology (Provide sufficient detail such that an unaware reader could repeat the described data collection procedures.)
Five experimental plots (=blocks) were located at each site. The blocks were chosen subjectively to include the range of local soil and vegetation conditions at each site. Each block contained 16 tubes that were used to collect NH3 lost from in situ soil columns subjected to one or more experimental treatments. Tubes, mad of 30-cm lengths of 10- cm diameter PVC pipe, were pounded into the soil for half their length on 8-10 June 1988.
After a 10-day equilibration period, NH3 was collected in each tube for 24 h using 10 ml of 2% H2SO4 in a small open vial. During the collection the tubes were covered with aluminum foil held with a rubber band. Silicon grease was used to ensure a tight seal between the tube and the foil covering. This initial collection was made to compare natural rates of NH3 volatilization from all soils before experimental manipulations. To further characterize the initial conditions, soils collected from each plot were measured for water content (% mass loss after 48 h at 110 C), pH in 10 mM CaCl2, and concentrations of NH4+ and NO3- in 2 M KCl extracts.
On 20 June 1988, four experimental treatments, comprising a full factorial design with one replicate per block, including an unmanipulated control, were imposed on each block. Wet tubes received 220 ml distilled water (2.75 cm), chosen to bring the 15-cm soil column to field capacity (0.01 MPa potential) as determined from the moisture tension release curves of Schlesinger et al. (1987). Fertilized tubes received 10 ml of water containing 70 mg of N as NH4Cl, to achieve 10x the typical NH4+ pool found in the surface soils at this site (Lajtha and Schlesinger, 1986). Tubes with added organic C received 10 ml of water containing 26 g sucrose, chosen to add approximately 10x the natural amount of labile organic C to the soil. Finally, N- serve (Nitrapyrin) was added to tubes, using 10 ml of a solution of 3.67 g/l mixed in acetone to achieve the field concentration of 20 mg/kg recommended by Bundy and Bremner (1973) to inhibit nitrification. In each block, treatments were randomly assigned to tubes, and all solutions were applied to the surface, except for N-serve, which was injected to about 5-cm depth using a 0.89-mm dia needle. NH3 was collected during 24-h periods beginning on 21 June and 23 June and a 7-day period beginning on 29 June, using the procedures described above. The tubes were left uncovered between collection times to allow the normal course of soil drying.
Treatment of data: (List any programs used in analysis of the data):
[Note: Programs should be appended and stored with this form.]
Input data include the collection period (l to 4) representing pretreatment (l) and three posttreatment (24 hr = 2, 48 hr = 3, and l wk (l68 hr) = 4) collections of volatilized ammonia. Collections were made in 3 vegetation zones (G=grassland at the base of Mt. Summerford, C = creosotebush zone, and P = College Playa). Column 3 indicates the experimental block in each zone ( l to 5), Columns 4 to 5 indicate the tube in each block; this specifies the treatment via the if-then statements below. Tubes were randomized differently in each block. Dependent variables measured were ammonia collected in the scintillation vial, with data expressed in mgN/l in the acid collecting solution. This multiplied by l250 to reflect the volume of the solution and the area of the collecting tube gives nitrogen volatilized as ammonia in ugN/m2/day. Because period 4 was 7 days long, the daily rate of volatilization is vol/7 as created in the if-then statement on line 6. Finally, column l2 (+/-) shows whether ants were observed in the scintillation vial. Note that these tubes were deleted from all subsequent data analysis.
//DCALIC JOB DU.D02.ZI1603
// EXEC SAS DATA VOLATILE;
INPUT TIME 1 VEG $ 2 BLOCK 3 TUBE 4-5 VOL 7-11 ANTS 12; IF ANTS = 1 THEN DELETE; IF TIME = 4 THEN VOL = VOL/7; IF TUBE = 1 THEN WATER = 1; IF TUBE = 1 THEN AMMON = 1; IF TUBE = 1 THEN SUGAR = 1; IF TUBE = 1 THEN NSERVE = 0; IF TUBE = 2 THEN NSERVE = 1; IF TUBE = 2 THEN AMMON = 1; IF TUBE = 2 THEN SUGAR = 1; IF TUBE = 2 THEN WATER = 0; IF TUBE = 3 THEN WATER = 1; IF TUBE = 3 THEN AMMON = 1; IF TUBE = 3 THEN SUGAR = 0; IF TUBE = 3 THEN NSERVE = 0; IF TUBE = 4 THEN NSERVE = 1; IF TUBE = 4 THEN SUGAR = 1; IF TUBE = 4 THEN WATER = 0; IF TUBE = 4 THEN AMMON = 0; IF TUBE = 5 THEN SUGAR = 1; IF TUBE = 5 THEN WATER = 0; IF TUBE = 5 THEN NSERVE = 0; IF TUBE = 5 THEN AMMON = 0; IF TUBE = 6 THEN WATER = 1; IF TUBE = 6 THEN SUGAR = 0; IF TUBE = 6 THEN NSERVE = 0; IF TUBE = 6 THEN AMMON = 0; IF TUBE = 7 THEN NSERVE = 1; IF TUBE = 7 THEN AMMON = 1; IF TUBE = 7 THEN SUGAR =0; IF TUBE = 7 THEN WATER =0; IF TUBE = 8 THEN WATER = 1; IF TUBE = 8 THEN NSERVE = 1; IF TUBE = 8 THEN SUGAR = 1; IF TUBE = 8 THEN AMMON =0; IF TUBE = 9 THEN WATER = 1; IF TUBE = 9 THEN NSERVE = 1; IF TUBE = 9 THEN SUGAR = 0; IF TUBE = 9 THEN AMMON = 0; IF TUBE = 10 THEN NSERVE = 1; IF TUBE = 10 THEN WATER = 0; IF TUBE = 10 THEN SUGAR =0; IF TUBE = 10 THEN AMMON =0; IF TUBE = 11 THEN WATER =0; IF TUBE = 11 THEN NSERVE =0; IF TUBE = 11 THEN SUGAR =0; IF TUBE = 11 THEN AMMON =0; IF TUBE = 12 THEN WATER =1; IF TUBE = 12 THEN NSERVE =1; IF TUBE = 12 THEN SUGAR =1; IF TUBE = 12 THEN AMMON =1; IF TUBE = 13 THEN AMMON = 1; IF TUBE = 13 THEN SUGAR =1; IF TUBE = 13 THEN WATER =0; IF TUBE = 13 THEN NSERVE = 0; IF TUBE = 14 THEN WATER = 1; IF TUBE = 14 THEN NSERVE =1; IF TUBE = 14 THEN AMMON =1; IF TUBE = 14 THEN SUGAR = 0; IF TUBE = 15 THEN WATER =1; IF TUBE = 15 THEN SUGAR =1; IF TUBE = 15 THEN AMMON =0; IF TUBE = 15 THEN NSERVE =0; IF TUBE = 16 THEN WATER =0; IF TUBE = 16 THEN NSERVE =0; IF TUBE = 16 THEN SUGAR =0; IF TUBE = 16 THEN AMMON = 1; CARDS;
Site location (Describe in sufficient detail that the site can be relocated):
Field investigations were made on the New Mexico State University Ranch, 40 km NNE of Las Cruces, N.M. in the Jornada Del Muerto Basin. The experimental plots were established at three sites along the desert Long Term Ecosystem Research (LTER) transect that crosses the alluvial piedmont of Mount Summerford in the Dona Ana Mountains. One site was located in a grassland dominated by Bouteloua eriopoda in the upper reaches of the piedmont. A second site was in a mid-slope position in a shrubland dominated by Larrea tridentata, an invasive desert species. The third site was located in an ephemeral dry lake, or playa, dominated by Panicum obtusum, at the base of the piedmont. Locations correspond to LTER sites:
G-SUMM (Mt. Summerford grassland)
C-SAND (creosotebush Sand site)
P-COLL (College Playa)
4 collection periods