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Plant Inventory
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Representative specimens of plants have been collected periodically beginning in September 1995. The plants are pressed, dried and preserved as herbarium specimens. Because Science II Prairie is small, the entire area is searched . All specimens are stored in a herbarium cabinet in 102 Science II, Department of Animal Ecology. Species identification and nomenclature follows Flora of the Great Plains (MacGregor et al 1986).
A total of 18
species of grasses and sedges have been recorded of which
6 species are introduced species not native to the United States.
Reed canary grass dominates a narrow strip along the sidewalk
on the south side next to Science I. Big bluestem, Canada wild
rye, little bluestem, prairie cordgrass and switchgrass have persisted
since the original plantings were made in 1973. A total of 71
species of forbs have been identified of which 48 species are
native prairie species.
Seedlings of six species of trees have been found of which one is non-native. Most of the trees have been found growing along the fence on the western side of the prairie next to the parking lot. It is probable that these trees grew from seeds transported in the droppings of birds that used the fence as a perch. Tree seedlings are removed each year in order to maintain the character of the prairie.
Only one species of shrub has been identified. Two plants of buckbrush, also known as coral berry, were found growing close together on the east side of the prairie in September 1995. Another individual of this species was found on the northwest corner of the prairie in 1998. Buckbrush is a common shrub that grows along prairie-woodland edges and often occurs as understory in open woodland or savannah.
On October 4, 1995, the restoration ecology class mapped the
distribution of 17 common plants occurring on the prairie. These
included nine grasses: switchgrass,
big bluestem, little bluestem, brome, cord (slough) grass, sideoats
grama, indian grass, Canada wild rye, and Reed canary, and 8 forb
species: field bindweed, compass plant, bergamot, thistle, goldenrod,
sunflower, gray-headed coneflower, and common burdock. Thistles
included 3 species (tall, field and Canada), and goldenrod 2 species
(stiff and tall). In 1996, the restoration ecology class again
mapped these and other species of plants and found little change
from the previous year. Plants were not mapped in 1997.
Methods
Prior to mapping, the prairie was divided into 4x4 m quadrats
(Figure 3). Each student was given a row
of quadrats to map. As the student entered a given quadrat, he/she
visually divided the quadrat into fourths and recorded the percent
of each of the grasses occurring in each 2x2 m quarter of the
quadrat. Percentages were estimated visually by the student. In
addition, stem counts were made of each of the selected forb species
occurring in each 2x2 m quarter of a quadrat, except that bindweed
and burdock were recorded as present or absent. The percentages
and stem counts for each quarter of each quadrat were then written
on the quadrat map for the entire prairie, and lines were drawn
around areas where given grasses and forbs occurred in the highest
proportions.
Data from the 2x2 m quadrats were entered into a spreadsheet
program (Microsoft EXCEL) and output produced in a comma delimited
ASCII format. This format allowed the data to be read by the program
SURFER (Golden Software, Inc). Data from 1995 and 1996 are stored
on a 3.5 in. floppy disk located at the ISU Cooperative Fish and
Wildlife Research Unit. A blanking file, used to outline the sidewalk
and the Science II building is also included on this disk.
SURFER is a graphics program that can interpolate contour
and three dimensional surfaces based on regular or irregularly
spaced sampling points. SURFER uses various methods to take spaced
data points and interpret the composition of the area between
these points. This interpretation permits the researcher to collect
reliable information with fewer samples.
Kriging was the surface interpolation method used in association
with the data collected from the Science II prairie. Kriging is
a geostatistcal gridding method developed for use by geologists
in mineral and oil exploration, but has also been found to be
useful in various other research fields. For further information
on Kriging and SURFER refer to D. Keckler (1994. Surfer for Windows.
Golden Software, Inc.)
Results. Distribution maps
produced with the SURFER program are linked to a brief description
of the plant.
In 1975, the dominant plant groups of the Science II Prairie were mapped (Figure 1). In addition, a map of frequently occurring plants was constructed (Figure 2). The methods for the 1975 data collection and map construction were either not documented or the records concerning data collection were misplaced. Also, grasses and forbs were not mapped separately. As a result, a direct comparison of all dominant grasses and forbs in the prairie in 1975 and 1995 is not possible; however, it is possible to see a shift in the abundance and location of selected species.
Grasses that dominated some parts
of the prairie in 1975 (Figs. 1 and 2) had shifted to other areas by 1995 (Fig. 4). For example, switchgrass expanded
its distribution and was the most prevalent grass on the prairie
in 1995, whereas in 1975 it did not seem to dominate such a large
area. Sideoats grama also shifted south of where it was reported
in 1975 (Fig. 4). The distribution of Indian
grass shifted in dominance from the southeast corner in 1995,
where it was dominant in 1975, to the middle of the prairie. Little
bluestem was found only in small patches on the east side of the
prairie in 1995 and it did not dominate any portion of the prairie
as it had in 1975. Interestingly, reed canary grass dominated
a large portion of the southern edge of the prairie in 1995, but
this species was not mentioned as either a dominant plant or a
frequently occurring plant in 1975 (see discussion in history
section). Reed canary grass was probably seeded into a disturbed
area along the south edge of the prairie in the late 1980's. It
should be kept in mind that other grasses were interspersed with
the dominant grasses. Big bluestem, for instance, was found over
much of the prairie in 1995, but was dominant only in a small
section at the west edge.
The following discussion of the changes in forb species from
1975 to 1995 is based on comparisons of Fig.2
(Plants Occurring Frequently, October 1975), with Fig.
5, (Distribution of Dominant Forb species, 1995).
In 1995, bergamot occurred as a dominant forb species in many
quadrats of the prairie, whereas this species did not appear on
the 1975 map. Other forb species occurring in 1995, but not reported
in 1975, included greyhead coneflower, thistle, bindweed, and
common burdock.
Compass plant, sunflower, and goldenrod appeared in the southern portion of the prairie in 1975. In 1995 compass plant occurred in the eastern third of the prairie; it is possible that compass plants along the south edge of the prairie were destroyed when the University telephone lines were buried along the sidewalk in 1988. Sunflowers were located in six small scattered areas across the prairie, and goldenrod was found in the southwestern/south central and the northern regions of the prairie. Several forbs, which frequently occurred in 1975, but infrequently in 1995, included yellow (gray-headed) coneflower, aster, verbena (vervain), black­eyed susan, prairie clover, and purple cone flower. Rattlesnake master (Eryngium yuccifolium) was present (although not abundant) in the early years of the prairie but was absent in 1995. (This section updated August 1998.)
Selected Plant Descriptions and Surfer Distribution Maps
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