This study was conducted in a Bouteloua eripoda grassland in Pasture 9
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.
Also available are soil moisture data from this study in data package
knb-lter-jrn.210278001.
