Playa selection and characterization
We consulted the Jornada Basin landform map and available aerial
imagery to choose 30 out of 99 potential playas that encompassed a
broad range of sizes, catchment characteristics, and proximities
to different geological features. The perimeter of each playa was
ground-truthed using a Trimble Geo 7X handheld GPS (Trimble
Navigation Limited, Sunnyvale, CA).
Sampling and laboratory analyses
In each study playa, we collected 36 soil samples of 100 g each
using a 70 mm diameter one‐piece hand auger (Forestry Suppliers
Inc., Jackson, MS). The soil samples were collected from nine
locations along two perpendicular transect lines to account for a
topographic gradient from the edge of the playa to the center of
the playa. At each of the nine locations, one sample was collected
at four depths (0–10 cm, 10–30 cm, 30–60 cm, 60–100 cm). Each soil
sample was dried at 105°C for 24 h, homogenized, sieved through
2 mm mesh screen, and frozen before analysis.
The prepared playa soil samples were first acid fumigated to
eradicate inorganic carbon (Harris et al. 2001) and then ground in
a ball mill. Soil carbon and nitrogen content were measured using
elemental combustion analysis to determine organic carbon (Sollins
et al. 1999). We weighed 45mg subsamples of fumigated soil into
silver tins and combusted them using an ECS 4010 elemental
analyzer (Costech Analytical Technologies, Valencia, CA, USA) to
estimate organic carbon (g C/g soil) and total nitrogen (g N/g
soil).
We also estimated soil bulk density (g/m3) from three locations at
each sample depth for all 30 playas using the core volume sampling
method. The soil weight and core volume were recorded using
methods from Elliot et al. (1999) The resulting bulk density
measurements for each depth range (m) were used to convert soil C
and N measurements (g/g) to organic carbon and nitrogen stocks per
unit area (g/m^2).
Full details on methods and associated analyses are available in
the publication by McKenna and Sala (2016).
Related data packages
knb-lter-jrn.210420002 - Chloride ion concentration in a subset of
the playas in this dataset for calculating groundwater recharge
rate.
There are also some upland soil datasets in the associated paper
(below) that are available on request from the JRN data manager
(datamanager.jrn.lter@gmail.com) until they are published on EDI.
References
Elliot, E. T., J. W. Heil, E. F. Kelly, and H. C. Monger. 1999.
Soil structural and other physical properties. Pages 74-88 in G.
P. Robertson, C. S. Bledsoe, D. C. Coleman, and P. Sollins,
editors. Standard Soil Methods for Long-Term Ecological Research.
Oxford University Press, New York, New York.
Harris, D., W. R. Horwath, and C. van Kessel. 2001. Acid
fumigation of soils to remove carbonates prior to total organic
carbon or carbon-13 isotopic analysis. Soil Science Society of
America Journal 65:1853-1856.
Sollins, P., C. Glassman, E. A. Paul, C. Swanston, K. Lajtha, J.
Heil, and T. E. Elliott. 1999. Soil carbon and nitrogen pools and
fractions. Pages 89-105 in G. P. Robertson, C. S. Bledsoe, D. C.
Coleman, and P. Sollins, editors. Standard Soil Methods for
Long-Term Ecological Research. Oxford University Press, New York,
New York.
McKenna, Owen P., and Osvaldo E. Sala. "Biophysical controls
over concentration and depth distribution of soil organic carbon
and nitrogen in desert playas." Journal of Geophysical
Research: Biogeosciences 121, no. 12 (2016): 3019-3029.
https://doi.org/10.1002/2016JG003545
