Nutrient losses in runoff from grassland and shrubland habitats in southern New Mexico: I. Rainfall simulation experiments --Nitrogen and phosphorus chemistry

Study number: 

381

Data set ID: 

210381001

Data Access: 

Unrestricted

Dataset status: 

Date range: 

1995-06-01 to 1996-07-31

Original investigator: 

William H Schlesinger

Data contact: 

Abstract: 

This data set was collected to provide data for comparison of the losses of dissolved nitrogen and phosphorus in the runoff from grass- and shrub- dominated plots in the Jornada Basin of southern N

ew Mexico. This dataset contains the following columns: Plot: the identification number for the plots, which are grouped for grass, shrub or intershrub areas. Fill Time: the time in seconds used to collect an individual sample of discharge from the plot. Time: the time in minutes (from the beginning of the rainfall simulation) at which each individual collection of discharge began. In each case, the first time listed is the time at which discharge was first observed. Time b/w samples: the time in seconds between the beginning the collection of a given sample of discharge and the beginning of the next collection. Q: the rate of discharge during each collection, in cubic centimeters per second. AveQ/time: the total discharge during an interval in cubic centimeters. For example, the discharge between 16 and 20 minutes is calculated as the mean of the discharge at l6 and 20 minutes multiplied by 4 minutes. InorgN-rain (adjusted inorganic N): the concentration of NH4-N + NO3-N in the discharge sample collected, corrected for the sum of the concentration of these ions in the simulated rainfall applied. Concentration is given in milligrams per liter for N contained in the sum of these forms. Analysis for NH4-N and NO3-N was performed using the Bran-Luebbe Traacs 800 Autoanalyzer, as detailed in Schlesinger et al. (l999). Total N-rain (adjusted total N): the concentration of total dissolved N in the discharge sample collected, corrected for the concentration of total dissolved N in the simulated rainfall applied. Concentration is given in milligrams per liter of total dissolved N in the sample. The concentration of total dissolved N was performed using the Traacs 800 Autoanalyzer, following a persulfate digestion of the sample, as detailed in Schlesinger et al. (l999). OrgN-rain (adjusted organic N): the concentration of N contained in dissolved organic forms, corrected for the concentration of dissolved organic N in the simulated rainfall applied. Dissolved organic N is calculated as the difference, in any sample, between the total dissolved N and the sum of NH4-N and NO3-N. Values are in milligrams per liter. Total P-rain (adjusted total P): the concentration of total dissolved phosphorus, corrected for the concentration of total dissolved phosphorus in the simulated rainfall applied, both in milligrams per liter. Org-P-rain (adjusted org P): the concentration of dissolved organic phosphorus, corrected for the concentration of dissolved organic phosphorus in the simulated rainfall applied, both in milligrams per liter. Inorg-N-rain (adjusted inorganic N), the yield in grams of NH4-N plus NO3-N in the discharge collected. TotalN-rain (adjusted total N), the yield in grams of total dissolved N in the discharge collected. OrgN-rain (adjusted organic N), the yield in grams of forms of dissolved organic N in the discharge collected. Total P-rain (adjusted total P), the yield in grams of total dissolved phosphorus in the discharge collected. OrgP-rain (adjusted organic P), the yield in grams of forms of dissolved organic phosphorus in the discharge collected. InorgN-rain (adjusted inorganic N) load, is the rate of loss, in grams per second, of the sum of NH4-N plus NO3-N during the period of the sample collection. Total N-rain (adjusted total N) load, is the rate of loss, in grams per second, of total dissolved N during the period of the sample collection. OrgN-rain (adjusted organic N) load, is the rate of loss, in grams per second, of dissolved organic N during the period of the sample collection. Total P-rain (adjusted total P) load, is the rate of loss, in grams per second, of total dissolved P during the period of the sample collection. Org-P-rain (adjusted organic P) load, is the rate of loss, in grams per second, of dissolved organic P during the period of the sample collection.

Data download: 

Description: 

Data file information for the following Jornada data set: Nutrient losses in runoff from grassland and shrubland habitats in southern New Mexico: I.

Rainfall simulation experiments --Nitrogen and phosphorus chemistry

Methods: 

Field data sheets for field data collection. Instrumental for analysis by autoanalyzer.

Rainfall simulations in the grassland were performed on six plots, each 1 x 2 m in dimension. Plant cover in each of these plots was about 50%, composed of individual clumps of Bouteloua eriopoda, which are typically each about 20 cm in diameter. In the shrubland, 1 x 1 m plots were centered on individual shrubs (n=8) or in bare areas between shrubs (n=10). The 1 x 1 m size was selected for these plots so that the shrub plots would not extend beyond the perimeter of the shrub canopy. A field-portable rainfall simulator, developed and described by Luk et al. (1986), was used to apply water at a nominal rate of 140 mm/hr to these plots. This simulator delivers rainfall with 90% of the kinetic energy of natural rainfall and a comparable drop-size distribution. All rainfall simulations were performed during the dry season, during June 1995 and 1996, on initially dry soils. Each simulation lasted 30 minutes, and the actual rainfall delivered to each plot was measured in an array of 6 wedge-shaped raingages located around the periphery of each plot. The mean rainfall intensity was 146, 118, and 136 mm/hr during the rainfall simulations on grassland, shrub, and intershrub plots, respectively. Runoff rates (discharge) were determined by taking timed volumetric samples of the water discharged from a trough placed along the lowest side of the plot. Once runoff commenced, it increased rapidly, so samples of the outflow were initially collected at 30-s intervals. Later in the experiment, when runoff stabilized, samples were collected at longer intervals ranging from 2 to 4 min. Samples were collected in polypropylene bottles. The duration of the sampling lasted 15 s early in the experiment and ranged from 20 to 30 s later in the experiment, depending on the fill time of the sample bottle. Following each simulation, the surface cover of fines (i.e., materials <2 mm diameter), gravel (material >= 2 mm), plant litter, and vegetation was estimated for each plot using a grid of 200 points. Runoff samples were filtered through pre-rinsed 0.45 micron Millipore HA filters, and analyzed for NH4, NO3, and PO4 using standard methods on a Traacs 800 Autoanalyzer. Inorganic N is taken as the sum of NH4-N + NO3-N. Each sample was then subjected to a persulfate digestion (D'Elia et al. 1977) and reanalyzed. The difference between the digested and undigested concentrations is assumed to represent dissolved organic forms of N and P. Contents of N and P in the applied water were subtracted from the contents in runoff to estimate the net losses in runoff.

Additional information: 

The grassland studied was located on the alluvial piedmont of Mount Summerford near the powerline road running along the base of Mt. Summerford. The location of the simulations is south of the LTER-I Alternate Control Transect and immediately north of the LTER-I Hydrology Natural Runoff Plots but downslope of the powerline road.

Maintenance: 

June 1995 and 1996

Date Data Last Updated: 

1996-07-31

LTER Core Area(s): 

Data category: 

Research Network: