Experimental design
This study was conducted in a Bouteloua eripoda grassland in
Pasture 13 of the Jornada Experimental Range in Dona Ana County,
New Mexico, USA. In 2006, 36 2.5m x 2.5m plots were established in
each of three blocks on a level upland with flat slopes protected
from livestock grazing since 1996. The experiment was implemented
as a randomized complete block design with 2 factors:
precipitation manipulation (3 levels) and nitrogen fertilization
(2 levels).
The 3 levels of precipitation manipulation were 1) 80% reduced
precipitation, 2) ambient precipitation, and 3) 80% increased
precipitation. Reduction of 80% precipitation was achieved with
rainout shelters with transparent acrylic troughs that acted like
shingles. An irrigation system was used to implement the water
addition treatments.
The two levels of nitrogen fertilization consisted of 1) liquid
Ammonium nitrate fertilizer applied twice each growing season in
mid- and late July from 2006 to 2008 (treatment), and 2)
application of the same amount of water, equivalent to a 2mm rain
event (controls). The ammonium nitrate fertilizer consisted of 10
grams of ammonium nitrate dissolved in water per meter per year.
Treatments began in 2007.
Treatment combinations were randomly assigned to plots within each
block. Six replicates were used for each treatment combination
yielding total 36 plots per block.
Sensor descriptions and data collection
Shallow probes (Campbell Scientific CS625) began collecting data
in mid-2011. Six plots were selected from each precipitation
treatment group (total of 18) for soil moisture probe
installation. For these surface probes, the CS625 probe was
installed in a vertical configuration to measure soil water
content from the upper 0-30cm layer of the soil profile.
Shallow probe data were collected in this manner until 2018, with
intermittent long gaps in the record, including in early 2013,
fall 2015 to fall 2016, and summer 2017 to summer 2018.
Deep soil moisture probes (Campbell Scientific CS650 or CS655???)
were installed and began recording data in the summer of 2018. The
probes were installed into an excavated soil pit to monitor soil
moisture from 50-60cm depth. The sensors were installed at a 45
degree angle. Due to the location and permeability of soil
carbonate layers, there is variation of up to ten centimeters in
the depth of the lower sensor across plots. Intermittent gaps in
the record continued until 2022.
In 2022, the shallow CS625 probes were replaced with Campbell
Scientific CS655 probes and the dataloggers were replaced with the
CR300 series. The sites were connected to the Jornada wireless
network, which should reduce missing data periods going forward.
Soil volumetric water content (VWC, cubic meters H20 per cubic
meter soil) is measured every minute by dataloggers (Campbell
Scientific CR200x or CR300) and averaged into hourly values for
each sensor. Hourly data tables were downloaded a few times
annually via USB port on a field tablet computer (Lenovo S10-3t)
with Campbell Scientific PC200W or PC400 software. Data are
missing from some probes during periods of disconnect or
malfunction, and "NA" values are used to fill
accordingly. Datalogger records are checked for date/time
completion using R. The included data table contains daily
averages of soil VWC from surface and deep sensors, as well as
plot and treatment information.
Related data and publications
Plant cover and biomass data from this study can be found in EDI
data package knb-lter-jrn.210349001.
For further information and results, see:
Throop, H., L. G. Reichmann, O. Sala, and S. Archer. (2012),
Response of dominant grass and shrub species to water
manipulation: an ecophysical basis for shrub invasion in a
Chihuahuan desert grassland. Oecologia 169: 373-383.
https://doi.org/10.1007/s00442-011-2217-4
Reichmann, L. G., O. E. Sala, and D. P. C. Peters. (2013), Water
controls on nitrogen transformations and stocks in an arid
ecosystem. Ecosphere 4(1):11. https://doi.org/10.1890/ES12-00263.1
Reichmann, L.G., Sala, O.E. and Peters, D.P.C. (2013),
Precipitation legacies in desert grassland primary production
occur through previous‐year tiller density. Ecology, 94: 435-443.
https://doi.org/10.1890/12-1237.1