Methods:
Field micro-cassette tape recorders
Study Site and Experimental Design Description A creosotebush shrub
study site and a black grama grassland study site have been
established at each of the Sevilleta, Jornada and Mapimi research
locations. Each study site is 1 km by 0.5 km in area. Three rodent
trapping webs and four replicate experimental blocks of plots are
randomly located at each study site to measure vegetation responses to
the exclusion of small mammals (see Figures 1 & 2 for diagrams of
the two Jornada sites). The blocks of study plots are all oriented on
a site in a 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 creosotebush site is oriented to the
south. Treatments within each block include one unfenced control plot
(Treatment: C; control), one plot fenced with hardware cloth and
poultry wire to exclude rodents and rabbits (Treatment: R; rodent),
and one plot fenced only with poultry wire to exclude rabbits
(Treatment: L; lagomorph), and one plot fenced with barbed wire to
exclude cattle (Treatment B; bovine). Note that there are cattle
exclosure plots only at the Jornada grassland site where cattle are
present, for a total of 4 measurement plots at each of the grassland
site blocks. There are only 3 measurement plots at each of the
creosotebush site blocks. The treatments were randomly assigned to
each of the four possible plots in each block independently, and their
arrangements differ from block to block. Each of the plots in a
replicate block are separated by 20 meters (see Figure 3). Each
experimental measurement plot measures 36 meters by 36 meters (see
Figure 4). A grid of 36 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. The 36 quadrats are
numbered 1-36, starting with number 1 in the top left corner of each
plot, and running left to right, then down one row, and then right to
left, and so on (see Figure 4). A 2-foot rebar marks the lower right
corner of each quadrat, and an aluminum tag on the rebar gives the
quad number. 3-inch nails were originally placed in the top left
corner of each quadrat. These may be difficult to see. A 3-meter wide
buffer area is situated between the grid of 36 points and the
perimeter of each plot. Working on the Study Plots Always avoid
walking on the quadrats, and do not walk across plots or anywhere
within a block unless absolutely necessary. We are attempting to
measure the effects of rodents and rabbits on plants and soils, not
the effects of humans. When working on a plot, always walk on a line
just below the rebar and quadrats, or on a line to the right of the
rebar and quadrats (see dotted lines in Figure 4). Please try to walk
gently and flat-footed on the study plots to minimize soil
disturbance. When placing the vegetation measurement frame on a
quadrat, be careful not to disturb the soil with the frame legs or
your feet. When leaning over the measurement frame, be careful not to
put your foot on the quadrat. We must measure all human caused
disturbances to the soil surface of each quadrat. Vegetation Quadrat
Measurements The foliage canopy area and maximum height of each plant
species is measured from each quadrat. Several other variables are
also measured from each quadrat, including soil surface disturbance,
soil surface leaf litter cover, soil surface cryptogam crust cover,
termite mud casing, and number of rabbit feces. All cover values are
measured from the vegetation measurement frame, which is 1 meter by 1
meter, and partitioned into a grid of 100, 10 cm by 10 cm squares.
Cover is measured by counting the number of 10cm squares that are
occupied by the foliage canopy of a particular plant species, or by
the soil disturbance, leaf litter etc. Portions of the 10 cm squares
are also measured, down to 0.1 of a square. Detailed descriptions of
measurement techniques are given below for each of the different
variables measured. Placement of the vegetation quadrat measurement
frame Walk from quadrat to quadrat along the lines mentioned above and
marked in Figure 4. When you reach a quadrat, place one leg of the
frame immediately next to and touching the 2-foot rebar, over the
quadrat. Place the leg for the opposite corner of the frame (from
bottom to top of a diamond shape) just inside of the 3-inch nail
located at a 315 degree angle from the rebar on the plot X/Y, and
compass coordinate system. The frame should be positioned so that the
sides are parallel to the sides of the plot and directly over the
quadrat, and in line with the rows of rebar (see Figure 4). You may
not be able to see the nail, if not, line the sides of the frame with
the rows of rebar the best you can. Recording Data You will record the
quadrat data into your tape recorder. Each time you start recording
data from a new plot (even if you are just helping someone else finish
a plot), always start your recording by stating: "These are
vegetation quadrat measurements for the Jornada small mammal exclosure
study." Then state the date (month, day, year), the site (G or
C), the block (1,2, 3, or 4), the plot (1, 2, 3, or 4), and the
treatment (C, R, or L). If you are helping someone else on a plot,
state so, and record who the other person is. Go to the first quadrat
you will be taking measurements from, and record the quadrat number
(1-36) before you start recording data, by stating "starting
quadrat (n)". Note that (n) means whatever the appropriate number
or letter is. When you are finished recording data for that quadrat,
state "finished with quadrat (n)." Then go on to the next
quadrat, and so on. When you have finished collecting data from the
plot, state "finished with quadrat measurements on plot (n), of
block (n), at site (n), on (date)." Additional Observations,
Corrections, and Comments If you have already recorded data for a
variable, e.g., rabbit feces, but while looking over the quadrat
later, see some more, you may either make a correction to the
previously recorded values, or make another observation (e.g.,
"correction, rabbit feces count (n)", or "rabbit feces
count (n)." At any time, if you realize that you recorded
incorrect data, just state "correction, ....." Always start
corrections with the statement "correction". Do not try to
run-back the tape and re-record over mistakes, just state
"correction", and mention the problem. For comments, state
"comment" and then record whatever you want to say about
something. Comments are useful if you are uncertain about something,
or see something unusual. Try to minimize use of comments though.
Checking Your Tape Recordings Be sure to frequently play-back a small
portion of your tape to verify that the tape recorder is working
properly. Stop and play-back at least at the end of each line of 6
quadrats. Checking your tape after every other quadrat is even better.
Labeling Your Tapes Be sure to label your tape, both on the cardboard
case insert, and directly on the tape. Use the following format to
label your tape: e.g., SMESVQF96-DL2 Where: SMES = small mammal
exclosure study VQ = vegetation quadrat data F96 = fall 1996, or S96
for spring 1996 DL2 = initials for your name, in this case Dave
Lightfoot, and the number of the ape, in this case, my second tape.
Procedures for Vegetation Quadrat Measurements Below is a listing of
procedures and values and ranges of values that you should record for
each of the variables measured on the vegetation quadrats. IMPORTANT
NOTE!!! Be sure to record an entry for all six of the following
variables, even if the measurement or count is zero. So, for example,
if there are no rabbit feces, record "rabbit feces count
zero" or if there is no termite casing, record "termite
casing zero" etc. Get into a routine of examining each quadrat
for each of the 6 variables. For example, start with plant cover,
starting with the dominant plant species, then look for leaf litter,
then look for cryptogams, then look for soil disturbance, then look
for rabbit feces, then look for termite casing. And be sure to record
a value for each of the 6 variables for each quadrat. Rabbit Feces
Count the total number of rabbit feces (pellets) that you see on each
quadrat. State "rabbit feces, count (n)." Place all rabbit
feces from all quadrats on one plot into the same bag. Be sure that
the bag is labeled with the date, site, block, plot, and treatment.
Additional information:
A creosotebush shrub study site and a black grama grassland study site
have been established at each of the Sevilleta, Jornada and Mapimi
research locations. Each study site is 1 km by 0.5 km in area. Three
rodent trapping webs and four replicate experimental blocks of plots
are randomly located at each study site to measure vegetation
responses to the exclusion of small mammals. The blocks of study plots
are all oriented on a site in a 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 creosotebush site
is oriented to the south. Treatments within each block include one
unfenced control plot (Treatment: C; control), one plot fenced with
hardware cloth and poultry wire to exclude rodents and rabbits
(Treatment: R; rodent), and one plot fenced only with poultry wire to
exclude rabbits (Treatment: L; lagomorph), and one plot fenced with
barbed wire to exclude cattle (Treatment B; bovine). Note that there
are cattle exclosure plots only at the Jornada grassland site where
cattle are present, for a total of 4 measurement plots at each of the
grassland site blocks. There are only 3 measurement plots at each of
the creosotebush site blocks. The treatments were randomly assigned to
each of the four possible plots in each block independently, and their
arrangements differ from block to block. Each of the plots in a
replicate block are separated by 20 meters. Each experimental
measurement plot measures 36 meters by 36 meters (see Figure 4). A
grid of 36 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. The 36 quadrats are numbered 1-36, starting
with number 1 in the top left corner of each plot, and running left to
right, then down one row, and then right to left, and so on. A 2-foot
rebar marks the lower right corner of each quadrat, and an aluminum
tag on the rebar gives the quad number. 3-inch nails were originally
placed in the top left corner of each quadrat. These may be difficult
to see. A 3-meter wide buffer area is situated between the grid of 36
points and the perimeter of each plot. Rodent trapping webs are being
used to determine the composition of rodent species at each study
site, and to estimate densities of each species over time. The use of
webs and distance measures to estimate rodent densities is
statistically more robust than grid plot sampling and mark-release
indices. Each rodent trapping web consists of a series of 12 equally
spaced lines radiating from a central point. Each line consists of 12
trap stations. The first trap station is located 5 meters from the
center, the next three at 5 meter intervals, and the remaining 8 at
ten meter intervals. Each trap line is 100 meters long, and each web
is 200 meters in diameter.
Maintenance:
Twice each year through 1995: April and October Once every 5 years
after 1995: October for Grass sites
