The goal of this project is to determine the nature and magnitude of changes in the hydrologic properties of arid soils with increasing amounts of pedogenic calcium carbonate. The amount and morphology of the calcium carbonate in arid soils varies laterally and vertically with changes in the age of the soils, thus the hydrologic properties also vary systematically The calcium carbonate cements soil particles changing the apparent texture of the soil horizon and thus other soil properties such as structure, porosity, moisture retention, and unsaturated and saturated hydraulic conductivity also change significantly. There has been no systematic study of the impact of increasing amounts of calcium carbonate on the hydrologic properties of semi-arid soils. The ultimate goal of this study is to provide a basis for developing more accurate pedotransfer functions, which are the main methods for obtaining soil hydrologic properties of rangeland soils.
Selection of Surfaces: Three terraces of different ages were chosen at the outlet of a small watershed basin at the base of Sierra Ladrones in North West Sevilleta National Wildlife Refuge. These surfaces have shown varying stages of calcic horizons.
Digging Pits: 3 Pits up to a meter deep were dug on each surface.
Describing the Soils: the soil profile in each pit was described using USDA soil survey guidelines.
Soil Sampling: From every pit, soil samples were collected every 10 cm. Also soil peds were collected from every horizon for bulk density analysis.
Infiltration Experiment: In order to check the soil hydraulic conductivity, a tension disk infiltrometer was used on every soil horizon in each pit.
Laboratory Analysis: The soil samples were split and sieved for laboratory analysis
CaCO3 Content: The total inorganic carbonate content was calculated using Chittick’s apparatus
Bulk Density: The bulk density of the soil peds was calculated using the Clod’s apparatus.
PSDA: Particle size distribution analysis was carried out with the presence of carbonate on the 2mm sample.
Carbonate Digestion: The carbonate was digested to remove the amount of carbonate from the sample. PSDA was performed again on the soil samples without the carbonate.
Information on Collection Sites:
Study Area 1:
Study Area Name: Surface 1(Pit 1)(Young Surface)
Study Area Location: Outlet of the small watershed basin at the base of Sierra Ladrones
Study Area Description:
Elevation: 1623 m
Geology: Quaternary Sierra Ladrones Formation
Soils: Laborcita-Pilabo-Lemitar complex
Climate: Semi arid, Rainfall ~ 250 mm
North Coordinate: 34° 24.5’
West Coordinate: 106° 58.1'
Study Area 2:
Study Area Name: Surface 2 (Pit 2)(Intermediate Surface)
Elevation: 1615 m
Geology: Quaternary Sierra Ladrones Formation
Climate: Semi-arid, Rainfall ~250 mm
North Coordinate: 34° 24.491'
West Coordinate: 106° 58.046'
Study Area 3:
Study Area Name: Surface 3 (Pit 3) (Oldest Surface)
Elevation: 1633 m
Climate: Semi-arid, Rainfall~250 mm
North Coordinate: 34° 24.405'
West Coordinate: 106° 58.020'
Other Field Crew Members: Ritchie Andre and Ramirez Carlos
In 1984, a research project was initiated on a relatively small disturbance patch just south of Deep Well. This disturbance was thought to be the result of an old praire dog town, probably dating back to when a nearby ranch was active, and a lot of old mammal mounds remained in the disturbed area. One of the things that made the disturbance patch particularily noticeable was the lush growth of snakeweed (Gutierrezia sarothrae) within the patch. This prompted the designation of the disturbance patch as the "snakeweed patch" or "Gutierrezia patch." In addition, there was an obvious increase in bare ground and a shift in vegetation composition across the patch boundary. The dominant vegetation was not consistent around the boundary, with a marked dominance of black grama on the west side of the plot and a blue/black grama mix on the other three sides. To obtain information on the cause and/or effect of this disturbance, a survey of the soil and vegetation was performed.
Sample collection - The soil samples were collected using a hammer-driven soil corer. The barrel of the corer was fitted with a plastic sleeve that allowed extraction of the soil core generally intact. The soil corer was driven to a depth of 50 cm and soils split ito 10 cm fractions. This data set contains data for only the top 30 cm.
Samples were taken along six 100 m transects. Four of these transects crossed the patch boundary on the four cardinal points. On these four transects the 0m sample was taken starting 50 m outside the boundary, the 50 m sample was taken at the patch boundary and the 100 m sample was taken 50 m into the patch. The other two transects formed a cross near the center of the patch.
Twenty-one cores were collected along each transect, with increased sampling intensity near the boundary. However, this data set contains data from only the 10 m intervals for a total of 11 samples.
Sample processing - Soil samples were kept in a refrigerator prior to analysis. Each sample was weighed and samples were well-mixed before analysis. Samples were sieved through 2mm screens to remove pebbles and roots. A sample of 25 g was added to a preweighed soil can. Samples were dried for 24 hours at 105 degrees C then cooled and then reweighed. This dry/wet moisture correction was used to calibrate weights for other samples. A 1 g sample was taken from the oven-dried samples and ashed at 500 degrees C for 2 hours and re-weighed after cooling. This provided a measure of organic content. A 12 g sample was weighed into a 125 ml plastic bottle and 100 ml of 2 N KCL added before the bottles were well-shaken. After standing for 24 hours, the KCL was decanted and the samples analyzed for NO3-N and NH4-N on a Technicon Autoanalyzer. Another 5 g sample was weighed into a centrifuge tube and extracted repeatedly with pH 7 ammonium acetate. These samples were brought up to 250 ml and analyzed for Ca, Mg and K using atomic absorption. Fifty g samples of soil were mixed and texture determined using the hydrometer method. Samples were mixed 2:1 with 0.001N CaCl2 and pH measured. From the oven-dried samples 1 g samples were digested using sulfuric acid using the Kjeldahl method. Samples were then brought up to 250 ml and analyzed on a Technicon Autoanalyzer for total nitrogen and phosphorous.
Coordinates (NAD27): End ofTransect Transect Latitude Longitude North 0 34 21' 1.2" 106 41' 8.3"W 100 34 20' 57.9"N 106 41' 8.6"W East 0 34 20' 47.0"N 106 41' 1.6"W 100 34 20' 46.5"N 106 41' 5.4"W West 0 34 20' 53.7"N 106 41' 16.3"W 100 34 20' 53.7"N 106 41' 12.4"W GCSA 0 34 20' 49.1"N 106 41' 9.2"W 100 34 20' 45.6"N 106 41' 9.2"W GCSB 0 34 20' 47.1"N 106 41' 8.9"W 100 34 20' 47.4"N 106 41' 5.1"W
12/10/00 (DM) File created.2/10/2009. (DM) Metadata was updated and compiled.