A DEMOGRAPHIC AND ECOLOGICAL ANALYSIS OF GEOCARPON MINIMUM (CARYOPHYLLACEAE): A FEDERALLY THREATENED SPECIES IN SOUTHWEST MISSOURI

2006·10.2 MB·English

by  Tim Smith

AND
A DEMOGRAPHIC ECOLOGICAL OF
ANALYSIS
GEOCARPON MINIMUM A
(CARYOPHYLLACEAE):
SOUTHWEST
THREATENED
FEDERALLY MISSOURI
SPECIES IN
Tim
Smith^ S.E
Missouri Department of Conservation Department of Biology
P.O.Box 180 Central Missouri State University
Jefferson City, Missoun 65 102-01 80, U.S.A Worrensburg, Missouri 64093, U.S.A.
ABSTRACT
A
Gcocarpon minimum population growing on a sandstone glade in Dade County, Missoun was monitored for ten
years (1994-2003). Plants were counted annually in eight perrnanent plots at two scales (0.01 and 1.0 m-) to determine
and
population fluctuations through time. Soil depths as well as cover of bryophytes, lichens, vascular plants, bare
minimum
rock/soil were recorded in subplots between 1994 and 2000 to determirie any possible association with G.
numbers. The number of G. minimum plants in the eight plots varied from to 4230, with a inean of 1332. Mean soil
1
<
depth of subplots containing G. minimum was 19 mm. There was a weak association (r, = 0.16, P 0.001) between soil
G
depth and Geocarpon density. Regression analyses show that minimum numbers tend to increase with increasitig
mm
among
soil depth to about 20 and dechne thereafter, In addition, there were significant differences vegetation
< minimum
types (P 0.05) with the exception of lichens (P > 0.05). There was a significant difference between G.
population numbers and year (P < There w^as discontinuity with scale and the Spearman rank correlations,
0.05),
however, when ecological groups were combined into larger categories lichens and bryophytes were lumped
(i.e.,
into cryptogams), patterns were clearer across scales. Documentation of bare rock areas indicates a dynaniic process
of soil movement into and out of plots, but cover data did not indicate a consistent increase in coverage of moss, vascu-
mum
lar plants, or hchens duriiig the ten yeai's of the study It is concluded that G, nn' n utilizes habi tats with periodic soil
i
Although bank was
disturbance and with minimal competition from bryophytes or perennial vascular plants. seed
not a subject of this study, importance was evident from annual census data that showed the population is capable
its
rebounding dramatically following years with virtually no seed production.
of
RESUMEN
Una poblacion de Geocarpon minimum fue monitoreada durante diez anos (1994-2003J en un afloramiento de
arenisca y suelo poco profundo en el condado de Dade en el estado de Missouri. Para determinar la luct uacion del
t
nijmero de plantas en la poblacion durante el periodo de estudio, las plantas se contaron anualmente en ocho
parcelas permanentes usando dos escalas (0.01 y 1.0 m-). Durante los at'ios 1994 hasta el 2000 fueron evaluados
datos sobre profundidad de suelo, cobertura de briofitas, liquenes, plantas vasculares y area de tierra o rocas sin
numero
plantas en subparcelas con proposito de determinar la posible asociacion de estas variables con el de
el
plantas de G. minimum. El numero de plantas de G. ininimum en las ocho parcelas vario de 1 a 4230 con un
minimum mm.
promedio de 1332. La profundidad promedio del suelo de las subparcelas con G. fue de 19 La
minima
asociacion entre profundidad de suelo densidad de plantas de Geocarpon fue (r^- 0.16, P < 0,001). El
la y
demostroque numero minimum aumentar medida que profundidad de
anahsis de regresion de G. parece a la
el
mm
(P<
suelo alcanza los 20 y disminuye a mayor profundidad- Ademas, la diferencia entre tipos de vegetacion
0.05), con excepcion de los liquenes (P>- 0.05), fue significativa. La diferencia fue significativa tambien entre el
numero de plantas de G. minim [an y el afio del muestreo (P < 0.05). Se observe una discontinuidad entre escala y
las correlaciones de rango de Spearman, sm embargo, al combinar los grupos ecologicos en categorias mayores
mas
(por ejemplo, los liquenes y las briofitas se unieron en la categoria de las criptogamasj, los patrones fueron
un
claros a traves de las escalas. La documentacion sobre areas de afloramiento de rocas indica la existencia de
no
proceso dinamico de movimiento del suelo dentro y fuera de las parcelas, pero los datos sobre cobertura indi-
can un crecimiento constante de cobertura de musgos, plantas vasculares o liquenes durante los diez ai^os del
estudio. La conclusion es que G. m nimu m utiliza habitats de suelos que estan cambiando constantemente y tienen
i
poca competencia de briofitas plantas perennes vasculares. Aunque el banco de semillas en el suelo no se investigo
y
mo.gov
Tim Smith, corresponding author:TeIephone: (573) 522-41 15;Fax:[phone]; E-mail:tim.smith@mdc.
SIDA22(2):n45-1157.2006
1146 BRILORG/SIDA
22{2)
En minimum
en esrc csrudio, su imporrancia fue cvldenrc, base a los claros anuales, csta poblacion de G. ticnc la
capacidad para rcproducirse considcrablcmcnte en anos siguientes aunquc no cxista produccion dc scmilla en
afios anteruircs.
INTRODUCTION
m
Gcocarpon min urn Mack. (Caryophyllaceac) is a tiny, succulent winter annual that grows
i
on sandstone glades in Missouri, on saline soil prairies in Arkansas and Louisiana (U.S.
&
Fish and Wildlife Service 1993; Mclnnis et al 1993; Orzell Bridges 1987), and on saline
barrens in Texas (Keith et al. 2004) (Fig. The diminutive height of the plant (up to 4 cm),
1).
inconspicuous and
its flowers, its limited distribution are probably responsible for not
it
having been described until 1914 (Mackenzie 1914). Taller plants are usually multi-stemmed
mm
and The
many-flowered. smallest plants are only a few in height and produce just one
flower Both morphologies are often present in a single population, requiring surveyors to
acquire a broader search image to locate the full range of plant forms. Plants turn from a
brown
whitish-green wine-colored they mature and
to to light as senesce.
minimum
Gcocarpon was designated by the Fish and Wildlife Service
U.S. as a feder-
m
ally threatened species 1987 because of low population numbers Fish and Wildlife
(U.S.
known
Service 1987). It is today from fewer than 35 sites (Nicnaber 2005). TwentyTour ex-
tant Missouri populations know^n from Pennsylvanian-age sandstone
are glades seven
in
southwestern counties, giving a state rank of S2 (Missouri Dept. of Conservation 2006).
it
The
sandstone glades occur in the Springfield Flam subsection of the Ozark Flighlands
and
ecological section are considered imperiled (a rank of S2) because of their rarity within
minimum
the state (Nelson 2005). G. considered extirpated from type localityjasper
is its
County where may
Missouri, suitable habitat have been due land-use changes.
lost to
known
was management
Prior to this study, about the requirements main-
little for
minimum
taining populations range
of G. or the of year-to-year population fluctuations.
Several sites for the species occur on public lands where lack of information has led to a
management
lack of action. There was concern that some periodic disturbance might be
On many
necessary to maintain suitable microhabitat for G. minimum. of the glades where
the species occurs, the thin soil near the rock/soil interface dominated by dense mats
is
where
of moss, except trampling, off -road vehicle use, or water flow have maintained
areas of loose sand. The purpose of this study was gather long-term monitoring data
to
that could provide needed insights for effect! ve management of G. minimu m populations.
Specific objectives of this study were
to;
minimum
1) provide a long-term census of G. at the Flint Hills Glade
site,
determine
2) the correlation of bryophytes, lichens, vascular plants, and depth
soil
minimum
on
the G. population,
management
provide recommendations
3) for the conservation of this species.
MATERIALS AND METHODS
Study
Site
The
study site, Flint Hill Glades, located in Dade County Missouri, near Stockton Lake,
is
on land owned and managed by Army Corps
the Engineers Gcocarpon
U.S. of (Fig.
2).
minimum
was
discovered at Flint Hill Glades during a 1989 survey for the species
& m
(Thurman
Hickey The one impoundment
1989). site is atypical respect; the of Stock-
ton Lake inundated the creek valley below the glade and floods the lower portions of the
glade during extremely high which summer
lake occurred during
levels, the of 1993.
SMITH AND ECOLOGICAL ANALYSIS OF GEOCARPON MINIMUM MISSOURI 1147
ELY, IN
minimum
Geocarpon plant. Photo by Rick Thorn
Fig. 1
.
estimated that less than five-percent of the six-acre glade area suitable habitat
It is is
m
for G. minimum, which grows greatest abundance in shallow sand- and pebble-filled
depressions in the sandstone bedrock that are often devoid of other plants (Fig. Based
3).
on Dade County Morgan optimum
research another (1986) reported that habitat
at
site,
was found in zones of shallow soils (1~5 cm) over sandstone bedrock. These microhabi-
tats are maintained by flow of water over the bedrock that deposits sand and pebbles
into the depressions. Water flow can also carry away previous deposition and prevent
An
lichen or vascular plant succession. intermittent drainage flows through the study
carrying runoff from adjacent grazed pasture on private property into Stockton Lake
site
at the lower edge of the glade.
Much mat
of the surface bedrock covered by a thick of mosses (principally
is
&
Polytrichum ohiense Ren. Card.) intermixed with lichens, liverworts, and a few vascu-
lar plant species. Areas of deeper soil within the glade support grasses, shrubs
(e.g.
Muenchh.
Vaccinium arhoreum Marshall) and dwarfed Quercus marilandica
trees
(e.g.
A minimum
and mc/anchierar rea(F.Michx.)Fernald).Geocarpon plants were observed
bo
in the grazed portion of the glade on adjacent private land during the course of this study.
They are found only near a bedrock exposure where pasture grasses are not established.
The dense beds of moss found on the study site are not present in the pasture. The tram-
may
pling from cattle help to maintain the loose sand particles that accumulate to form
mum
maybe minimum
The
G. mi nf microhabitats. pasture area a source of G. seed for the
No
monitoring area. monitoring plots were established in the pasture, primarily because
management
grazing not viewed most publicly-owned
cattle is as a realistic tool for sites.
Data
Collection
m
m
X
Ten plots were established at the site in April 1994. The 1.0 1.0 quadrats were sub-
1148
BRIT.ORG/SIDA
22(2)
Fig. 2. Aerial photograph of Flint Hill Glade system, Stockton Lake, Dade County, Missouri.
minimum
jcctivcly located in areas containing G, in close proxniiity to areas dominated
by Two
mosses, lichens, or perennial vascular plants. opposite corners of each plot were
marked masonry
by nails driven into holes that were drilled into the bedrock.
Two
of the original ten plots eventually were dropped from the study because they
»
SMITH AND ECOLOGICAL ANALYSIS OF GEOCARPON MINIMUM MISSOURI 1149
ELY, IN
Fig. 3. Habitat at Flint Hill Glades. Photo by Tim Smith.
minimum
any
did not support G. after 1994. Inundation of part of the glade in 1993 cre-
ated temporary habitat in these plots due to silt and sand deposition with little vegeta-
tive competition. At one plot, sand and was deposited into a patch of bryophytcs on
silt
bedrock, temporarily providing habitat that supported minimum. The bryophytcs had
G.
been killed by the prolonged inundation and were soon gone, leaving only bare rock at
subsequent surveys. The other plot was located near the lake shore and included essen-
tially bare sand after the inundation, although had deep enough soils to support pe-
it
minimum when
rennial vascular plants. Although G. was found in the plot was estab-
it
lished in 1994, this plot thereafter became covered with debris from subsequent rises in
the lake level and no longer contained exposed sand or G. minimum,
m m
A
1 X 1 (1.0 m^) wooden frame was used to monitor the permanent plots. Fly-
m-
was on
fishing line strung the inside of the quadrat to further subdivide the 1.0 plots
cm x cm The number minimum was
into 100 subplots of 10 10 (0.01 m^). of G. plants
recorded in each subplot. Soil depth was measured at the center of each subplot by using
a nail to probe to bedrock and then measuring the length of the nail that had entered the
was was
Bare rock recorded as zero depth. Vegetative cover estimated using seven
soil. soil
Daubenmire and dominant was
cover classes (a modified cover class) cover character-
(Daubenmire The
ized as mosses, lichens, vascular plants or bare rock/soil 1959) seven
cover classes were: (0-1%), 2 (1-5%), 3 (5-25%>), 4 (25-50%), 5 (50-75%), 6 (75-95%) and 7
1
(95-100%).
In the spring ol 1995, three additional plots were established within the study area,
in moss-dominated areas that did not contain G. minimum. These plots were created by
m m
removing a x section of dense moss to expose underlying mineral soil or bed-
1 1
BRILORG/SIOA
1150 22(2)
2500
2000
1500
Numbers
of plants
1000
500
6
Plot
Plot 7
10
2001
Monitoring year
2002
2003
Fig. 4. Numbers of Geocarpon minimum plants in permanent plots from 1 994 to 2003.
These were subsequently monitored minimum.hui and cover
rock. three plots for G. soil
measurements were not taken.
Data
Analysis
minimum
The subplot (0.01 m^) values of G. numbers, soil depth, and cover classes for
summed
and
each vegetation type (see above) were within each large plot 1.0 m-^)
(i.e.,
were subsequently used for all analyses (Spearman rank correlation, analysis of vari-
and The independent were depth (mm),
ance, regression analyses). variables year, soil
and cover values of bryophytcs, lichens, and vascuLar plants. Lichens and bryophytes
were combined into a single category (cryptogams) and vascular plants and cryptograms
were combined mto smgle category
also a of total vegetation.
&
Spearman
rank correlation coefficients, (Zar 1999; Sokal Rohlf 1995) were cal-
r^,
culated on both subplots and large plots in order to determine strength of association
among minimum,
G. year, soil depth, bryophytes, lichens, cryptogams, vascular plants,
m^
and two and
total vegetation at spatial scales (0.01 1.0 m-). In addition, partial correla-
tions were also determined on ranked data controUing for the effect of year to determine
among
and
potential associations the vegetation types
soil.
number
Model regression analyses were performed with the of subplots that con-
II
minimum
dependent and depth independent
tain G. as the variable soil as the variable.
The regression analyses were performed on subplots only. Note that both soil depth and
number minimum normal
the of subplots that contain G. follow a distribution, as indi-
SMITH AND ECOLOGICAL ANALYSIS OF GEOCARPON MINIMUM MISSOURI
ELY, IN 1151
>
cated by a Kolmogorov-Smirnov normality test (P 0.05). Specific regression analyses
mm
mm.
were performed independently on depth range 20 and The
soil of to 21 to 110
1
was show minimum
justification for the latter to that the subplots containing G. increase
mm
with increasing soil depth to 20 and declines thereafter
A
Friedman repeated measures (FRM) analysis variance (ANOVA) non-para-
of
(a
ANOVA)
was determme
metric equivalent to the parametric repeated measures used
to
among numbers minimum
differences population annually Natural log transformed
G.
numbers was dependent was measures and
the variable, year the repeated plot
factor,
&
was the subject factor (Zar 1999; Sokal Rohlf 1995). Because some of the plots had zeros
and ones, was necessary to add a count of 2 (a constant) to each observation for natural
it
&
log (In) transformation (Zar 1999; Sokal Rohlf 1995). The transformation was done in
order improve models (Quinn Keough 2002) and maximally normal-
to statistical to
<Sr
ize the data. Independent variables, with the exception of year and plot, were treated as
&
random
in all models because they were not specifically controlled (Zar 1999; Sokal
minimum
Rohlf The year 1996 was excluded from analyses because only one
1995). all G.
plant was observed for that year and thus was considered as an outlier.
it
FRM ANOVAs
Additional were performed on cover classes of bryophytes, lichens,
vascular plants, cryptogams, total vegetation, and soil depth. There were three cover classes
and
for bryophytes, lichens, vascular plants, cryptogams, total vegetation while soil depth
FRM ANOVA
was placed into six. was performed on the large plots only Independent
ANOVAs
variables were natural log transformed as needed. Additional repeated measure
(Kruskal-Wallis) were performed without 1999 data in order to ascertain the relation-
ship between soil depth and vegetation groups without the possibility of an interacting
effect or confounding influence for the year 1999. The year 1999 was considered an out-
lier similarly to 1996 but with large numbers of Geocarpon observed for that year. The
was
alpha analyses
level for all 0.05.
AND
RESULTS DISCUSSION
Population Fluctuations
commonly
Winter annual glade plants exhibit annual fluctuations in population size.
Available moisture germination and spring growth can vary greatly with low
for fall
moisture making shallow-soiled areas hostile for plant growth. Long-term monitoring
is
important in order to document the range of fluctuations in population size. Knowledge
of this range improves our ability to interpret population data from sites where long-
The bank
term data are not available. ability of a species' seed to repopulate a site after a
poor seed production year has obvious implications long-term conservation.
for
minimum
Results of annual G. counts in eight plots are depicted in Figure The
4.
cumulative annual from ranged from one 4230
totals eight plots plant (1996) to plants
all
Although same amount and
(2003). all of the plots are the size, the quality of the G. mini-
mum
habitat within each plot varies, with some plots containing more bare rock or denser
vegetative cover. Plots 6 and which often contained the most Geocarpon, provide a
7,
greater percentage of thin soil with little competition from bryophytes, lichens, or vas-
The number minimum was
cular plants. small of G. plants at the site in 1996 probably
due to a prolonged dry period during early spring, prior to monitoring conducted in April.
minimum
Only one additional G. plant was observed outside of the plots during that
minimum
year's monitoring. More substantial numbers of G. were found at other sites in
the region that spring, indicating the critical effect of very local drought on the popula-
1152 BRIT.ORG/51DA 22(2)
No minimum was
tion at the study insect herbivory of G. observed at the study site
site.
<
or at any other Missouri sites. There was a moderate positive correlation (r^ = 0.44, P
m-
minimum was
0.001) of G. with year at the 1.0 scale (Tabic Plot to plot variation
1).
<
between 1997 and 1999 (RM: X^ = P = Tukey; - 4T6, P
significant 0.045; 0.05).
11.7, q
Although the population fluctuated from year to year depending on local conditions,
there was an overall increase in the population over the years.
Depth
Considerations
Soil
dynamic
The stream and sheet flow of water over the glade due to precipitation creates a
environment for G. minimum, with the depth and location of the loose, sandy soil with
uncommon m
was
small pebbles changing dramatically through time. not to find G. ni-
It
i
mum
plants that had been uprooted and probably displaced by water and movement.
soil
somewhat
seems likely that the succulent stems are at least tolerant of displacement
It
new when
become
and can established at locations, especially partially buried in sand.
mm
The mean soil depth for subplots containing G. minimum was 19 (Fig. 5a, b). In
comparison, Somers et (1986) found the shallowest soil depths on xeric communities
al.
of the limestone glades of Middle Tennessee to be (35 ± 17 mm), with such areas domi-
nated by annuals and mosses, including several endemic species. In this study, soil depth
was measured at the center of each subplot rather than at the actual location of any G.
minimum number
plant. Therefore the high of subplots with zero soil depth does not
cm
withm
imply that plants were growing on bare rock but rather that they grew about 7
(the distance from the center to a corner of a subplot) of the bare rock/soil interface.
was between depth and niinimum
Nevertheless, there a significant association soil G.
< m- < m-
numbers (r^ = 0.16, P 0.001 at 0.10 scale, r,= 0.41, P 0.001 at 1.0 scale)(Fig. 5b
and Note Spearman rank between depth and
Tabic that the correlation soil the Ire-
1).
m
minimum
quency of subplots containing G. was -0.46 (Fig. was observed that
5a).
It
Where
more
areas deeper perennial vascular plants were often present. vascular
ot soil,
plants become numerous, fallen leaves from trees can lodge between stems and accumu-
whereas G. mi nimu m-rich areas of the glade are windblown and/or washed by mov-
late,
ing water and remain largely free of leaves.
minimum
Shallow per not requirement growth. Rather, the
soil, se, is a for G. it is
mechanism by which plant competition minimized on the sandstone glades. This was
is
minimum
borne out by the growth of G. on deeper soils following removal of other veg-
etation and by prolonged inundation and wave action on the lower portions of the
litter
minimum
study in 1993. This also apparent with the observation that G. grows on
site
is
deeper soils in the saline prairies of Arkansas, Louisiana and Texas, wdiere high sodium
levels prevent the growth of competing vegetation. In addition, there were significant
differences with soil depth and the distribution of bryophytes, lichens, and vascular plants
m^
at the 0.01 scale as indicated by the Kruskal-Wallis analysis of variance and/or the
< <
Spearman rank correlation coefficients (bryophytes: H^ - 19.96, P 0.001, = -0.12, P
r^
>
H^ P P and H^ P =
0.001, lichens: - 19.10, = 0.002, r^ - -0.110, 0.05; vascular plants: - 17.18,
<
= P and
0.002, 0.445, 0.001)(Fig. Table
r, 5c, d, 1).
number minimum
Both soil depth and the of subplots that contain G. passed the
>
normality test (Kolmogorov-Smirnov P 0.05). The results of the model regression
II
mm
minimum
show
analysis that G. increases with increasing soil depth until about 20
<
= 4.45; P 0.05) albeit with a low adjusted r^ (15.4%). The regression model ac-
(Fi,
18
counted for teen percent of the variation and consistent with the results of the
if is
I
An
Spearman rank b and
correlations Table additional regression analysis
(Fig. 5a,
1).
1
SMITH AND ELY. ECOLOGICAL ANALYSIS OF GEOCARPON MINIMUM IN MISSOURI 1153
Spearman
Table rank correlation coefficient for Yea r,Geocarponm/n/mum,bryophytesJichens, vascular plants,
1.
=
cryptogams, total vegetation, and soil at the subplot (0,01 m-),n 862, (above the diagonal) and large plot (1.0
=
m^), n 50 (below the diagonal) scales. Correlations between large plot and subplot data (along the diagonal)
=
were not calculated because the data are not paired. * significance the 0.05
at level.
minimum
Year G. Bryophytes Lichens Vascular Cryptogam Total Soil
Plants Vegetation
-
Year 0.440^ -0.123^ -0,317* 0,022 -0.331* -0.537* 0.038
minimum 90 - -0.230* 68* 86* -0.305* -0.236* 62^
G. -0.1
0.1 0.1 0.1
-
*
Bryophytes -0.161 -0.098 -0.160* -0.577* 0.729* 0.362* -0.118
-
Lichens -0.184 -0.045 0.367* -0.442* 0.550* 0.298* -0.027
- * 65'
Vascular Plants -0.024 0.204 -0.1 54 -0.273 -0.781 0.070*
0.1
-
Cryptogam -0.283* 0.727* 0.829* -0.346* 0.542*
-0.099
-0.1
1
-
Total Vegetation -0,312* -0.041 0.663* 0.755* 0.120 0.871* 0.043
*
Soil 0.042 0.408* -0.1 99 -0.256 0.471 -0.222 0.448*
mm
minimum
shows numbers with depth beyond 20
that G. decrease increasing soil (F2,
<
gg = 68.45; P 0.0001) with an adjusted r^ of 43.1% (Fig. 5a, b). These results suggest that
minimum
numbers increase with increasing depth where competition mini-
G. soil at a
is
mum
but decreases The observation probably due the competition
thereafter. latter to
is
from perennial vascular plants, which are more prevalent on deeper
soils.
Vegetation Correlations
Large areas of the glade's sandstone bedrock are covered with dense bryophytes and
it
was expected that cover measurements would demonstrate that bryophytes were spread-
mum
ing into mini populations. Although bryophytes were negatively correlated with
G.
<
minimum numbers
G. at the subplot scale (r^ = -0.23, P 0.001), they were not at the large
minimum
plot scale. Similar results were observed with lichens and G. numbers in that
was
there a negative relationship at the subplot scale but not at the large plot scale (Table
among
Although some with two
there discontinuity scale the latter groups, there
is is
1).
<
P between cryptogams (combined
a strong negative association Us = -0.78, 0.001) cat-
minimum
egory of bryophytes and lichens) and G. numbers (Fig. 5f and Table The
1).
may minimum
cryptogam
latter suggest that competition a factor in depressing G.
is
populations.
A minimum
positive association occurred with coverage by vascular plants and G.
<
(r^ = 0.19, P 0.001) at the small plot scale but not at the next scale (Fig. 5e and Table 1). It
may minimum
be that through time G. has persisted only on those areas of the glade that
same make mosses and
are subjected to the periodic disturbances that difficult for vas-
it
cular plants to become established. Lichen cover declined steadily from 35.1% in 1994 to
would show
10.9% in 1998. Perhaps this aspect of the monitoring better statistical trends
conducted and with more with
over a longer period detailed data collection respect to
if
the species of vascular plants and cryptogams across population Certainly the
sites.
movement would numbers
of soil over the bedrock explain the erratic variation in of
minimum
subplots dominated by bare soil or bedrock. There arc similarities between G.
num-
population dynamics and winter desert annuals in that there are large population
Guo
ber changes from year to year. et (2002) discussed dramatic fluctuations in abun-
al.
among
dance, productivity, and diversity desert winter annuals. Furthermore, the popu-
dynamics Vulpia Link, has been well studied (Watkinson 2000;
lation of ciliata et
al.
& &
Watkinson Watkinson Davy 1985;Watkinson Harper This annual
1990; 1978). grass,
—
—
^
1154 BRIT.ORG/SIDA 22{2)
60
60 p<
o =0.16, 0.001
b
r
%
(0
^ 50
o
50
E
•
t
40
•
5 40
•
W
(3
30
30
*I»«^ft
20 20
* •
£i
CO
^
E
3
O 10
10
g
o
— —
—
—
—
^ __
^^^ ___^
1 ^
J
20 40 60 80 100
20 40 60 80 100
Depth (mm) Depth (mm)
Soil Soil
80
80 1 -
c
=
Tg 0.46, p < 0.05
,-
o
60
^
60
J3
c
1
40
Q.
40 .
^m IP VBftP ^V
^
CO
3
O
20
20
"^
o
IS
>
gg^
A
—
1
' f 1 T r F
20 40 60 80 100
20 40 60 80 100
(mm)
Depth
Depth (mm) Soil
Soil
60
S- 60
50
s
I
50
40
.§
c
40
30
30
c
o o
20
20 g.
s-
o O
o O 10
10
0)
20 40 60 80 100 20 40 60 80 100
Crytogam Cover
Total
Total Vascular Plant Cover
%
h
60
Flint Hills
500
Collins
50
400
o
40
.s
3
s
300
30
o
o
c
200
s- 20
O
0)
o
10
100
CD
20 40 60 80 100 1998 1999 2000 2001 2002 2003 2005
Total Vegetation Cover Year
Fig. 5. Scatter plots of G. minimum, soil depth (millimeters), other vegetation types, with corresponding Spearman rank correlation
coefficients and best fit lines, and population numbers of G. minimum from two populations (Flint Hills Glade and Collins relocation
Site, Dade and St. Clair counties, Missouri), t indicates significance only at the large (1 .0 m^) plot scale.