MONTANA STAlt LIBHAH1
3 0864 0010 3990 1
EFFECTS OF GRAZING ON ARABIS FECUNDA
1996 Progress Report
Peter Lesica
929 Locust
Missoula, MT 59802
STATE DOCUMENTS COLLECTION
1998
MONTANA STATE LIBRARY
u_ 1515 E. 6th AVE.
HELENA, MONTANA 53S20
In cooperation with Montana Natural Heritage Program
15 15 East Sixth Avenue
Helena, MT 59620-1800
For:
Bureau of Land Management
P.O. Box 3388
Butte, MT 59702-3388
Task Order 1422E070P60063
December 1996
This report should be cited as follows:
Lesica, P. 1996. Effects of grazing on Arabis fecunda - 1996 progress report to Bureau of Land
Management. Montana Natural Heritage Program, Helena. 5 pp plus appendices
lllV" ill II II III III III
3 0864 0010 3990 1
EFFECTS OF GRAZING ON ARABIS FECUND A
1996 Progress Report
STATE DOCUMENTS COLLECTION
I998
MONTANA STATE LIERARY
Peter Lesica m£*?&m%$%620
929 Locust
Missoula, MT 59802
In cooperation with Montana Natural. Heritage Program
15 15 East Sixth Avenue
Helena. MT 59620-1 SOO
For:
Bureau of Land Management
P.O. Box 3388
Butte, MT 59702-3388
/
Task Order 1422E070P60063
December 1996
This report should be cited as follows:
Lesica, P. 1996. Effects of grazing on Arabis fecunda - 1996 progress report to Bureau of Land
Management. Montana Natural Heritage Program, Helena. 5 pp plus appendices
INTRODUCTION
Arabis fecunda Rollins is a rosette-forming perennial in the Mustard Family
(Brassicaceae). This recently described species (Rollins 1984) is endemic to highly calcareous,
azonal soils in the foothills of the Sapphire Range in Ravalli County and in the Pioneer and
Highland ranges of Beaverhead and Silver Bow counties, Montana (Lesica 1993). Arabis
fecunda generally occurs on steep, often eroding slopes with low vascular plant density. Arabis
fecunda is considered threatened in Montana (Lesica and Shelly 1991) and is listed as a sensitive
species by the U.S. Forest Service and the Bureau of Land Management.
Most sites at which Arabis fecunda occurs are grazed by livestock, but little is actually
known about the effects of livestock grazing on this rare species. Studies have shown that A.
fecunda is more common on soil occupied by cryptogamic soil crust (Lesica and Shelly 1992).
These crusts are easily disturbed by livestock grazing; consequently, grazing may reduce A.
fecunda populations at these sites (Lesica and Shelly 1992). Furthermore, A. fecunda often
occurs on steep slopes with unstable soil. Trampling by livestock could reduce the number of A.
fecunda plants on these slopes. On the other hand, A. fecunda seems to require open soil for
seedling establishment (Lesica and Shelly 1996) and may be facilitated by disturbance associated
with grazing at some sites. The purpose of this study is to determine the effects of livestock
grazing on populations of Arabis fecunda. on the north side of the Pioneer Range.
STUDY SITES
Quartz Hill: From Dewey travel west on Hwy 43 ca. 0.3 miles and then turn south on gravel
road (Beaverhead Forest Road #187). Proceed ca. 1 mile up the road. Exclosure is on a steep
hillside west of the road (T1S R10W S8 NW1/4 of SE1/4). Aspect: 95°, Slope: 40° Elevation:
5,900 ft.
Thompson's Corner: From Dewey, travel west on Hwy 43 ca. 3.2 miles and then turn north on
gravel road (Beaverhead National Forest Road #83). Continue ca. 0.2 miles and turn east on a
small dirt road along the north side of the Big Hole River. Continue ca. 2 miles. Site is on the
north side of the road on the west side of a small draw. T1S R10W S5 NW1/4 of NW1/4.
Aspect: 100°, Slope: 20°, Elevation: 5,600 ft.
Dewev Cemetery: From Dewey travel west on Hwy 43 ca. 0.3 miles and then turn south on
gravel road (Beaverhead Forest Road #187). Proceed ca. 0.5 mile up the road to just past the
cemetery. Pull in on the small two-track going east just past the cemetery. Site is on the hill to
the south. Aspect: ca. 220°, Slope: 30° Elevation: 5,800 ft.
METHODS
Field Methods
The Quartz Hill and Thompson's Corner exclosures were established in 1991, while the
Dewey Cemetery exclosure was established in 1993. Measurements were made at the three sites
on the following dates:
Quartz Hill- 1 1 Jun 1 99 1 , 7 Jun 1 993
Thompson's Corner- 11 Jun 1991, 7 Jun 1993, 17 Jun 1996
Dewey Cemetery- 7 Jun 1993, 17 Jun 1996.
The Quartz Hill site was destroyed by vandals in 1995 or early 1996, before measurements could
be taken a third time.
There is one exclosure plot and one control plot at each site. Each exclosure plot is 6 ft X
6 ft, marked at the four corners by metal stakes and completely covered by firm wire mesh.
Control plots are placed near by the exclosure and are identical except they are uncovered. Each
plot is divided into four equal subplots (3 X 3 ft) to facilitate counting.
In each subplot estimate the basal cover of rock, moss-lichen, bare ground and
vegetation, and estimate the canopy cover of grass, forbs and shrubs to the nearest 5%. In each
subplot count the number of Arabis fecunda plants in each of three size classes:
Seedling (S):single rosette smaller that a penny
Rosette (R): single rosette larger than a penny or multiple rosettes
Fruiting (F):plants with flowers or fruits
Data Analysis
Changes in basal or vegetation cover between exclosure and control plots can be assessed
by visual examination of the summary tables.
There are no replicates of the treatments at any of the sites; thus, statistical tests based on
parametric distributions (e.g. t-test, analysis of variance) cannot be used. It is necessary to use
counts (frequency) and contingency table analysis. The ratio of Arabis fecunda plants in
treatment to control plots in year t can be compared to that in year t+a with a chi-square test.
This test assumes that the observations are independent; i.e., the plants counted in year t+a
cannot be the same as those counted in year t. Demographic monitoring studies from low-
elevation sites indicate that ca. 65% of cohorts have died after three years (Lesica and Shelly
1995). Thus, the test cannot be considered valid unless comparing counts taken at least three
years apart. Number of plants in each of the three size classes can also be compared using the
same test.
RESULTS
Changes in vegetation
Canopy cover of grass has increased in all the exclosure plots since the start of the study
but not in control plots (Table 1). Other changes are small and inconsistent and likely due to
recording error.
Arabis fecunda density
Only the 1991-96 and 1993-96 intervals can be tested for statistical significance. The
1991-93 interval is too short because well over 50% of plants alive in 1993 were probably also
alive in 1991 (Lesica and Shelly 1995).
At Thompson Corner density of A. fecunda increased in exclosure plots but not in control
plots in 1991-96 and the difference was significant for reproductives and total density (Fig. 2).
The difference between exclosure and control plots was greater in 1993 than in 1996. At Dewey
Cemetery density of A. fecunda increased in both exclosure and control plots in 1993-96, but the
increase was significantly more pronounced in the exclosure for rosettes and total density (Fig.
2). At Quartz Hill density of A. fecunda was higher in the exclosure in 1991, but higher in the
control in 1993. Unfortunately the significance of these changes cannot be tested statistically.
DISCUSSION
In the first years of the study density of A. fecunda became significantly greater in the
exclosures at both Thompson Corner and Dewey Cemetery, and most of this difference was due
to increases in the number of rosettes, indicating enhanced recruitment following cessation of
grazing. At Thompson Corner, the only site with three recording periods, the difference between
exclosure and control plots remained relatively stable between 1993 and 1996. On the other
hand, density of A. fecunda appeared to decrease in the exclosure plot relative to the control at
Quartz Hill. The reason(s) for this difference in response among the three sites is not known.
These results suggest that grazing or trampling have an adverse effect on A. fecunda populations
at some but not all sites. Grass cover increased in the exclosures at all sites as expected,
suggesting that livestock do use these areas. However, mule deer are also present, and there is no
W way to ascertain whether the positive effect of the exclosures on A. fecunda was due to exclusion
of cattle or deer or both.
Experimental plots at Thompson Corner and Dewey Cemetery should be vi sited again in
1999 to determine if the positive effect of the exclosures on A. fecunda continue to be manifest.
LITERATURE CITED
Lesica, P. 1993. Report on the conservation status of Arabisfecunda, a candidate threatened
species. Unpublished report to the U.S. Fish and Wildlife Sendee. Montana Natural Heritage
Program, Helena, MT.
Lesica, P. and J. S. Shelly. 1991. Endangered, threatened and sensitive vascular plants of
Montana. Montana Natural Heritage Program, Occasional Publication No. 1, Helena, Montana,
USA.
Lesica, P. and J. S. Shelly. 1992. The effects of cryptogamic soil crust on the population
dynamics of Arabisfecunda (Brassicaceae). American Midland Naturalist 128: 53-60.
Lesica, P. and J. S. Shelly. 1995. Effects of Reproductive Mode on Demography
and Life History in Arabisfecunda (Brassicaceae). American Journal of Botany 82: 752-762.
Lesica, P. and J. S. Shelly. 1996. Competitive effects oiCentaurea maculosa on the population
dynamics of Arabisfecunda. Bulletin of the Torrey Botanical Club 123: 111-121.
Rollins, R. C. 1984. Studies in the Cruciferae of western North America II. Contributions to the
Gray Herbarium 214: 1-18.
Table 1 . Basal and canopy cover of ground and vegetation in exclosure and control plots at three
study sites. Litter cover is combined with bare ground.
Quartz Hi
Rock
Bare Ground
Moss/lichen
Basal Veg.
Grass
Forbs
Shrubs
Rock
Bare Ground
Moss/lichen
Basal Veg.
Grass
Forbs
Shrubs
Rock
Bare Ground
Moss/lichen
Basal Veg.
Grass
Forbs
Shrubs
Exclosure
Control
1991
1993
1996
1991
1993
1996
0
13
..
0
10
..
-
73
--
83
--
-
2
--
--
1
-
14
-
--
8
--
0
19
-
4
8
--
3
25
4
14
--
2
8
Thompson':
3
; Comer
1
Exclosure
Control
1991
1993
1996
1991
1993
1996
48
50
34
34
36
20
..
31
18
-
53
60
-
4
3
3
<1
-
15
18
-
9
14
9
45
63
8
11
11
8
26
10
8
23
14
0
0
0
2
2
2
Dewey Cemetery
Exclosure
Control
1991
1993
1996
1991
1993
1996
41
16
„
38
29
54
68
-
58
64
1
2
-
1
<1
..
5
8
-
5
4
10
23
-
5
8
..
5
18
-
5
8
-
0
0
--
0
0
Table 1. Basal and canopy cover of ground and vegetation in
exclosure and control plots at three study sites. Litter cover
is combined with bare ground.
Que
trtz
Hill
Exclosure
Control
1991
1993
1996
1991
1993
1996
Rock
0
13
—
0
10
—
Bare Ground
—
73
—
--
83
--
Moss/lichen
--
2
--
--
1
--
Basal Veg.
—
14
—
--
8
--
Grass
0
19
--
4
8
--
Forbs
3
25
—
4
14
—
Shrubs
2
8
—
3
1
—
ThomDson's Corner
Exclosure
Control
1991
1993
1996
1991
1993
1996
Rock
48
50
34
34
36
20
Bare Ground
—
31
18
--
53
60
Moss/lichen
—
4
3
--
3
<1
Basal Veg.
—
15
18
--
9
14
Grass
9
45
63
8
11
'11
Forbs
8
26
10
8
23
14
Shrubs
0
0
0
2
2
2
Dewey Cemetery-
Rock
Bare Ground
Moss/lichen
Basal Veg.
Grass
Forbs
Shrubs
Exclosure
Control
1993
1996
1991
1993
1996
41
16
—
38
29
54
68
—
58
64
1
2
--
1
<1
5
8
—
5
4
10
23
--
5
8
5
18
—
5
8
0
0
—
0
0
Figure 1. Photographs of the Quartz Hill site and exclosure
taken in June, 1996.
n
Fiqure 2. Density of Arabis fecunda in exclosure and control plots at three
sites in 1991-96. Statistical significance determined by chi-square tests
*P<0.05, *** P<0.001.
Dewey Cemetary
Rosette
c
a
JUU
250
_
"o
200
150
0 -
- • / -
CD
E
100
50
0
•
i.i i
91 93 96
Thompson Corner
, Rosette
o
80
Q.
60
- /s -
n
/ °
40
- /
CD
-O
20
- /---. -
3
0
I I I
91 93 96
Quartz Hill
91 93 96
Reproductive
o Exclosure
• Control
Total
91 93 96
Year
Reproductive
400
*** _
300
f ~
200
1 ~
100
0
r
i
i i
91
93 96
Total
Reproductive
91 93 96
Total
91 93 96
MONTANA
STATE
This "cover" page added by the Internet Archive for formatting purposes
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11