Each study site is 1 km by 0.5 km in area. Four replicate experimental
blocks were randomly located at each study site depending on whether
the site was grazed. The blocks are all oriented on a site in an X/Y
coordinate system, with the access road to each site forming the X
axis. The compass orientation at the Jornada grassland site is to the
north, and Jornada creosote bush site is oriented to the south.
Treatments within each block include one unfenced control plot
(Treatment: C; control); one plot fenced with barbed wire, hardware
cloth, and poultry wire to exclude rodents, rabbits, and cattle
(Treatment: R; rodent); one plot fenced only with barbed and poultry
wire to exclude cattle and rabbits (Treatment: L; lagomorph); and one
plot fenced with barbed wire to exclude cattle (Treatment B; bovine).
Cattle exclosure plots with barbed wire occur only at the black grama
grassland site where cattle were present, for a total of 4 treatment
plots at each of the four grassland site blocks. There are only 3
treatment plots at each of the creosote bush site blocks. The
treatments were randomly assigned to each of the three or four
possible plots in each block independently, and their arrangements
differ from block to block. Each of the plots in a replicate block is
separated by 20 meters. Each plot measures 36 meters by 36 meters.
Thirty-six sampling points are positioned at 5.8-meter intervals on a
systematically located 6 by 6-point grid within each plot. A permanent
one-meter by one-meter vegetation measurement quadrat is located at
each of the 36 points.
100-meter measuring tapes were attached to the steel re-bar posts
marking vegetation quads 1, 3, and 5 on each study plot. The measuring
tapes were extended south to the re-bar posts marking quads 36, 34,
and 32. Data were recorded for all intercepts of live perennial plant
canopy foliage, and for bare ground. The start and end points for each
intercept were recorded to the nearest 10 cm on the measuring tape.
Intercepts less than 5 cm were ignored, and intercepts between 5 and
10 cm were recorded to the nearest 10 cm. Intercept measurements were
only recorded for perennial plant species (spp), and for bare soil.
Annual plants and dead perennial plants were ignored. The data were
entered in the field on to micro-cassette tape recorders. The taped
recorded data were then entered on to MS Excel spreadsheets. A macro
statement was used to subtract each observed intercept end measure
from the start measure, to produce an intercept measure for each
observation. Those data were then converted to space-formatted text
files, and combined as one file. The species list abbreviations (spp)
in the data table can be found here:
<ulink url="https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-jrn.210520001.1">https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-jrn.210520001.1</ulink>
This study is completed. Data was collected in 1995 and 2005.
