The plots receiving herbivore exclusion treatments in
experiment 64 are enclosed by a fence to exclude gophers and deer or gophers
alone. Plots are 12m x 12m. In plots receiving gopher removal treatment,
fencing material is buried 4 feet below ground. Plots receiving deer removal
treatment are surrounded by a deer fence that is 6 feet above ground. Those
plots with gopher/deer removal treatment, are 12m x 15m. A 3m strip along the
end of the plot farthest from the woods is fenced to exclude grasshoppers.
Mammal Trapping
Pocket gophers are trapped out of the plots
receiving gopher removal treatments, as soon as they appear. Gopher mounds
are then removed and vegetation is unburied.
Gopher mounds
Gopher mounds are mapped at 1-2 week intervals during
the growing season using the 10 x 10 grid of sample points for reference.
Mound maps are then used to determine the number and size of mounds in each
plot, and the total area that was disturbed each year.
Soils
A 10 cm deep soil core was taken at each of the sample points
when the plots were established. These samples were analyzed for total carbon
and nitrogen using a Carlo Erba CHN analyzer. These samples are archived for
future analyses.
Plots
Fifteen plots were established in 1989 along the south and east
margins of field 28, a field that was last cultivated in 1988. Plots were
placed 10 m from the forest-field
margin, with approximately 8 m between plots. Treatments are 1) unfenced
control, 2) gopher exclosure, and 3) gopher and deer exclosure. Gopher
exclosures were fenced with 1in mesh welded wire buried vertically from the
soil surface to a depth of 48in, and with a 24in width of 1in mesh welded wire
attached to the bottom of the vertical wire extending horizontally away from
the plot. Hardware cloth, 0.25in mesh, 24in wide, was attached to the top of
the vertical welded wire and held above ground with metal stakes. Gopher and
deer exclosures were fenced the same way as gopher exclosures, with the
addition of 6
Vegetation
Vegetation is sampled in mid-summer by recording all
species present in four 10 x 10 cm quadrats centered around each of the 100
sample points in each plot.
Trees
All trees have been mapped, tagged, and measured along the
forest-field margin
since 1992. Trees are mapped using stakes at the corner of each plot. Tree
height is measured as the maximum vertical height of the previous years
growth, measured from the base of the stem. The presence of browsing on
terminal or lateral branches is recorded for each tree.