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, 44 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 (5
levels) and nitrogen fertilization (2 levels).
The 5 levels of precipitation manipulation were 1) 80% reduced
precipitation, 2) 5-% reduced precipitation, 3) ambient
precipitation, 4) 50% increased precipitation, and 5) 80 increased
precipitation. Reduction of 80% or 50% precipitation was achieved
with rainout shelters having different numbers of 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 treatment combinations involving
ambient precipitation and four replicates were used for the
remaining treatment combinations, yielding total 44 plots per block.
Plant cover was sampled with a line intercept method in fall 2006
before any treatments began, then again in fall 2007 and 2008 after
treatments had been applied. Within each plot, green interception by
species was recorded for all plants present in the plot on 3 250cm
parallel lines evenly spaced from the east border. Plant cover was
later used to calculate plot biomass and then ANPP following
procedures in Flombaum and Sala 2007, and Sala and Austin 2000.
Also available are soil moisture data from this study in data
package knb-lter-jrn.210278001.
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.
<link xlink:href="https://doi.org/10.1890/ES12-00263.1">https://doi.org/10.1890/ES12-00263.1</link>
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/
<link xlink:href="https://doi.org/10.1890/12-1237.1">10.1890/12-1237.1</link>
