International Research Journal of Agricultural Science and Soil Science (ISSN: 2251-0044) Vol. 3(10) pp. 353-361,
October, 2013
DOI: http:/dx.doi.org/10.14303/irjas.2013.115
Available online http://www.interesjournals.org/IRJAS
Copyright ©2013 International Research Journals
Full Length Research Paper
Kochia prostrata establishment with pre-seeding
disturbance in three plant communities
Amy Sullivan T1, Val Jo Anderson2, Rachel Fugal A2*
1
Present Address: Biological Sciences Dept, University of Illinois at Chicago, 845 W. Taylor St. M/C 066 Chicago, IL
60607
*2
Present Address: 275 WIDB Brigham Young University Provo, UT 84602
*Corresponding Author’s E-mail: chelrann@gmail.com; Tel: (801) 422-3311; Fax: (801) 422-0008
ABSTRACT
Forage kochia (Kochia prostrata (L.) Schrad.), an introduced perennial capable of competing with
invasive species such as cheatgrass (Bromus tectorum L.), is being used for forage improvement and
wildland revegetation in the Great Basin and Intermountain West of North America. Because of its
ability to compete, there is concern that forage kochia may also be invasive. To test for potential
spread, we applied 4 disturbance agents (fire, soil, ATV, defoliation) at different intensities (low,
medium, high) in 3 plant communities (exotic annual, seeded with a mix of native and exotic
perennials, native shrub) and then seeded forage kochia. We replicated this design over 2 years, 1998
and 1999, and measured forage kochia density and cover through 2005. Precipitation was twice the
average in 1998 and less than half the average in 1999 in February and March, when most forage
kochia emergence occurs. Year of planting and the resident plant community affected forage kochia
emergence. The annual community had ten times as many emerged seedlings in 1998 than 1999, the
seeded community had twice as many seedlings in 1998 than 1999, and the shrub community had
similar seedling densities between 1998 and 1999 plantings. Disturbance only affected the 1999
planting, with highest initial emergence and slowest decrease in density occurring in soil treatments.
In 2005, forage kochia density was 4 times greater in the annual community than in the seeded
community for both the 1998 and 1999 plantings; cover was 20 times greater. Forage kochia virtually
disappeared from the shrub community by 2005. The results indicate that forage kochia is not
invasive in these plant communities at this site under the disturbance regime investigated.
Keywords: Forage kochia, invasive species, disturbance, establishment, fire, cheat grass, sagebrush, wheat
grass.
Abbreviations: all-terrain vehicle (ATV)
INTRODUCTION
Invasion of exotic plant species is a major threat to
native plant communities throughout the Intermountain
West in North America. Excess resource availability
negatively affects the resistance of plant communities to
invasion (Thompson et al., 2001). Contributing factors
to this excess may include incomplete resource use by
the resident plant community as a result of community
composition (Walker et al., 2005), fluctuations in
resource availability (Davis and Pelsor 2001), or
reduction in resource uptake by resident plants due to
disturbance (Burke and Grime 1996, Smith and Knapp,
1999; With, 2002). The introduction of disturbances
such as heavy grazing, change in fire frequency, and
all-terrain vehicle (ATV) traffic can weaken a community
and leave resources available to exotic invaders.
Invasive
exotic
species
vary
in
their
aggressiveness, preferred disturbance regimes (type,
frequency, and intensity of disturbance), and preferred
habitat. Although many attributes have been associated
with weedy plant species (Sakai et al., 2001), it is not
354 Int. Res. J. Agric. Sci. Soil Sci.
yet possible to accurately predict whether an introduced
plant species will be invasive in a particular area based
solely on phylogenetic or morphologic traits (Williamson
1999, Radosevich et al., 2005). Disturbance can be an
important factor in the spread and persistence of exotic
invasive species in native communities (Petryna et al.,
2002, Gelbard and Belnap, 2003). Additionally, some
exotic species exploit some types of disturbance better
than others. For example, a study of two invasive
cruciferous forbs in Germany (Bunias orientalis and
Rorippa austriaca) indicated that one increased with soil
disturbance, while the other increased at mown sites
(Woitke and Dietz, 2002). If a disturbance regime favors
the establishment and reproduction of an exotic
species, that species may be able to establish and
increase in communities where the disturbance regime
exists.
‘Immigrant’ forage kochia (Kochia prostrata (L.)
Schrad.), a semi-evergreen subshrub in the goosefoot
(Chenopodiaceae) family, was originally introduced
from Russia to compete with halogeton (Halogeton
glomeratus (Bieb.) C.A. Mey) and was released in 1984
(Stevens et al., 1984; Tilley et al., 2006). Many
consider it desirable in western North American
rangeland rehabilitation because it provides good
forage (7-14% crude protein during fall and winter
months, Davis 1979), is adapted to semi-arid lands, is
fire tolerant, remains high in moisture during the fire
season making it useful in greenstripping (Harrison et
al., 2002), and is competitive with exotic invasive
annuals such as cheatgrass (Bromus tectorum L.)
(McArthur et al., 1990, Monsen and Turnipseed, 1990),
halogeton (Stevens and McArthur, 1990), Russian
thistle (Salsola tragus L.), and medusahead
(Taeniatherum caput-medusae (L.) Nevski) (Stevens et
al., 1985; Tilley et al., 2006). Because of these
attributes, some scientists see forage kochia as a
solution to a multitude of problems facing wildlands in
the Great Basin and Intermountain West of North
America (McArthur et al., 1990; Clements et al., 1997),
while others view forage kochia as a potentially invasive
species (Mack, 1999). The objective of this study was to
evaluate the invasiveness of forage kochia by studying
the effect of 4 different disturbance agents applied as
single pre-seeding events on forage kochia emergence
and persistence in 3 different plant communities: one
dominated by annual grass, one dominated by
perennial grasses, and one dominated by perennial
shrubs.
by a native shrub community prior to 1994 when a fire
removed most of the vegetation. The soil (Hiko Peak –
Checkett complex) a deep, well-drained, gravelly loam,
is fairly suited to range seeding (Soil Survey Staff
2007) with low precipitation (174 mm/year, NOAA 1999)
and competing vegetation being the main factors
limiting success (Soil Survey Staff 2007). Subsequent
to the burn, one part of the area was rehabilitated by
drill-seeding a mix of natives and non-natives and is
now dominated by crested wheatgrass, sandberg
bluegrass, rubber rabbit brush, and sagebrush (Tab. 1).
The untreated portion now supports an exotic annual
community dominated by cheatgrass, with some bur
buttercup, and Russian thistle interspersed (Tab. 1). A
remnant of the unburned native sagebrush community
(Tab. 1) also exists next to the treated and untreated
burn. The result is an area with 3 adjacent community
types: exotic annual (hereafter referred to as annual),
seeded, and native shrub (hereafter referred to as
shrub).
This combination of communities on a large scale
presents an unusual and valuable research opportunity
with some notable limitations. Because the 3
communities were not created for the purpose of this
research, but rather developed as a product of nature
and practical management, these sites better represent
existing rangeland. At the same time, it must be
acknowledged that subtle differences in topography,
soil, and vegetation may have influenced the location of
the burn. Topography as well as resource limitations
also likely affected where the drill-seeding took place. In
addition to the differences in plant community
composition, these differences may have influenced the
results but we maintain that they do not compromise the
practical utility of this research. Plant community is one
of the most obvious measurable indicators and is used
throughout the Intermountain West to differentiate one
site from another. We only wish to acknowledge the fact
that there are likely other influential site characteristics
that affect not only the plant community but its response
to disturbance and invasion. Caution with interpretation
is necessary mainly due to the fact that there was no
opportunity to replicate the study site. Thus,
comparisons between plant communities must be taken
as suggestive and limited to the site rather than
definitive and broadly applicable. Although caution is
necessary in the interpretation of the results of such an
experimental design, the data are still a valuable
contribution to our understanding of forage kochia.
Design
MATERIALS AND METHODS
Study Site
Located on Dugway Proving Ground in western
Utah (40°15′13.74″ N latitude, 112°49′09.01 W
longitude), the study site was historically characterized
Three blocks of 15, 2 x 2 m plots were established in
each of the 3 communities. Four disturbances (fire, soil,
ATV, and defoliation) were applied at 3 different levels
(low, medium, and high), resulting in 12 disturbance
treatments in addition to 3 control plots. The plots were
randomly assigned within each block, though the ATV
Sullivan et al. 355
Table 1. Average vegetation aerial cover (%) and standard errors (in parentheses) for 3 adjacent plant
communities at Dugway, UT. (Gardner, 2009)
Picrothamnus desertorum Nutt.
Artemisia tridentata Nutt.
budsage
big sage
Native
Shrub
11.4
(2.1)
-
Atriplex canescens (Pursh) Nutt.
4-wing saltbush
Atriplex confertifolia (Torr. & Frém.) S.
shadscale
1.7 (0.9)
Wats.
Ericameria nauseosa (Pallas ex Pursh)
rubber rabbitbrush
Nesom & Baird
Chrysothamnus viscidiflorus (Hook.) Nutt. douglas rabbitbrush 0.2 (0.2)
Shrub total
13.3
(2.3)
Phlox hoodii Richards.
spiny phlox
Sphaeralcea munroana (Dougl. ex Lindl.)
munroe’s
Spach ex Gray
globemallow
Forb total
Agropyron cristatum L.
crested wheatgrass
Elymus elymoides (Raf.) Swezey
squirreltail
0.08
(0.1)
Poa secunda J. Presl
sandberg bluegrass
0.01
(0.01)
Achnatherum hymenoides (Roemer &
indian ricegrass
0.45
J.A. Schultes) Barkworth
(0.2)
Perennial grass total
0.5 (0.2)
Bromus tectorum L.
cheatgrass
12.3
(2.2)
Ceratocephala testiculata (Crantz) Bess.
bur buttercup
0.1
(0.03)
Salsola tragus L.
Russian thistle
Sisymbrium altissimum L.
tumble mustard
0.01
(0.01)
Annual weed total
12.4
(2.2)
disturbance treatment was restricted to the outside plots
to facilitate ATV access.
The fire disturbance was applied using a propane
torch to burn the vegetation in the plot. The low-level
fire treatment consisted of scorching the fine vegetation
close to the ground leaving some live material. All fine
vegetation was burned and the shrubs lightly scorched
for the medium-level treatment. All vegetation in the plot
was burned to the ground in the high-level fire
treatment. The soil disturbance was created using a
shovel to invert soil at approximately 20 cm depth
uprooting herbaceous vegetation and disturbing some
shrub roots. The soil texture (gravelly loam) created
minimal clods and air pockets. Less than 25% of the
plot was overturned in the low level, approximately 50%
for the medium, and more than 75% in the high. The
ATV disturbance treatment consisted of one pass of the
Seeded
0.01 (0.01)
Exotic
Annual
-
4 (1.4)
-
0.7 (0.6)
-
0.05 (0.05)
-
5 (1.7)
-
-
-
9.7 (2.3)
-
0.1 (0.07)
-
-
0.02 (0.01)
0.1 (0.07)
3 (0.6)
0.02 (0.01)
-
0.3 (0.1)
-
1.6 (0.5)
-
0.01 (0.01)
-
4.9 (0.9)
-
2.3 (0.8)
54.6 (3.1)
0.1 (0.02)
0.01 (0.01)
0.01 (0.01)
0.5 (0.2)
-
-
2.3 (0.8)
55.1 (3.02)
ATV with almost no vegetation or soil disturbance for
the low-level treatment, several passes (5-10) resulting
in vegetation disturbance but little soil disturbance for
the medium-level, and many passes (25-35) to the point
where soil surface disturbance was considerable and
the vegetation in the tracks was demolished for the
high-level. The defoliation disturbance was created
using a gas-powered weed-eater. The low level
treatment consisted of removing 50% (height) of the
vegetation in the annual (consisting of actively growing
fall-germinated cheatgrass) and seeded plots and
removing only the easily accessible herbaceous
understory in the shrub plots. The medium consisted of
removing 75% (height) of the vegetation in the annual
and seeded plots and removing the herbaceous
understory and lightly clipping the shrubs in the
shrub plots. The high level was created by removing all
Precipitation (mm)
356 Int. Res. J. Agric. Sci. Soil Sci.
Figure 1. Monthly precipitation recorded in 1998 (dark bars) and
1999 (clear bars) at Dugway Proving Ground, Utah. The line
represents the 36-year mean.
vegetation to the ground in the annual and seeded
plots, and removing all herbaceous vegetation as well
as most of the shrub foliage in the shrub plots.
Two weeks after treatment application, forage
kochia was seeded on 29-30 January 1998 (hereafter
referred to as the 1998 planting). A replicate of this
experiment was installed with treatments applied 2
weeks prior to planting on 16-17 February 1999
(hereafter referred to as the 1999 planting). The winter
seeding with forage kochia seed collected in Ephraim,
Utah the November before planting both years was in
accordance
with
recommendations
for
best
establishment (Tilley et al. 2006). Precipitation varied in
pattern and amount between 1998 and 1999 (Fig. 1)
with February-March receiving more than twice the
average precipitation in 1998 (85.9 mm; 36-year
average is 32.5 mm) and only 30% of average in 1999
(9.7 mm) (NOAA 1999). To simulate the seed density
and dispersal of mature plants in a rangeland setting
where stands are not pure and to ensure an even
dispersal across the plots, a 17.5 kg PLS/ ha seeding
rate was used for both plantings. To achieve this, 3.5 g
PLS were evenly broadcast by hand over each 2 m2
plot.
A 2 x 2 m PVC pipe quadrat subdivided into 100, 20
x 20 cm squares was used to collect data. We used a
stratified random sampling design and collected data
from 24 20 x 20 cm squares in each quadrat. In each
square, live forage kochia seedlings were counted, and
forage kochia cover estimated. The data from these
squares were averaged to yield forage kochia density
and cover for each 2 x 2 m plot. Density and cover data
were collected in June 1998, 1999, 2000, and 2002,
and May 2005.
Statistical Analysis
Data were analyzed using SYSTAT 10 (Systat, 2000).
Density data were square root transformed prior to
analyses to adjust for the Poisson distribution. Initial
analyses showed disturbance level was not significant,
so all levels were combined into one average of each
disturbance type per block for analyses. A multivariate
analysis of variance (MANOVA) was performed for both
plantings together with density and cover from the first
census for each planting (1998 and 1999 designated
year 1 for the first and second plantings respectively) as
dependent variables and planting, plant community, and
treatment as independent variables. An additional
MANOVA was done for both plantings together with
density and cover from the last census for each planting
(May 2005) as the dependent variables and planting,
community, and treatment as independent variables.
Repeated measures analyses of variance (ANOVAs)
were performed separately for the 1998 and 1999
plantings with forage kochia density for each census as
the dependent variables and community and treatment
as the independent variables. Figures are presented
using back-transformed means and standard errors for
ease of interpretation.
RESULTS
Density
Forage kochia seedling emergence differed between
planting years in relation to community and disturbance
treatment. The 1998 planting had more seedlings
Sullivan et al. 357
1998 Forage Kochia Planting
200
Density (#/m2)
150
Annual
100
Seeded
Shrub
50
0
1998
1999
2000
2002
2005
Figure 2. Forage kochia density in 3 plant communities over time following
the 1998 planting at Dugway Proving Ground, Utah. Repeated measures
ANOVA: community F8, 408 = 22.595, p <0.001. Bars represent standard error.
overall, with the highest density in the seeded
community and lowest in the shrub community (Fig. 2).
In contrast, seedling density remained highest in the
seeded community in the 1999 planting and was lowest
in the annual community (MANOVA: planting by
community F2,204 = 42.617, P <0.001) (Fig. 3). Forage
kochia emergence was unaffected by disturbance
treatment in the 1998 planting, while in the 1999
planting, the soil treatment had more seedlings than the
other treatments or control (MANOVA: planting by
treatment F4,204 = 2.662, P <0.05) (Fig. 3).
Plant community was the only factor that had a
significant effect on forage kochia density for the
duration of the study (1998-2005) for the 1998 planting.
Forage kochia density decreased less steeply and
leveled to 25 individuals/m2 in the annual community,
while it decreased to nearly 0 in the shrub community
(Repeated measures ANOVA: community F8, 408 =
22.595, P <0.001) (Fig. 2). In contrast, forage kochia
density in the 1999 planting for the duration (1999 to
2005) was influenced by a treatment by community
interaction (Repeated measures ANOVA: F24, 306 =
1.630, P <0.05) (Fig. 3). In the annual community,
density initially decreased and then steadily increased
to the end of the study. In contrast, density declined to
almost zero in the seeded and shrub community.
However, forage kochia decreased at a slower pace in
soil treatments in the seeded and shrub communities.
Cover
During the first year of data collection, forage kochia
cover was higher in the shrub community (1.5%) of the
1998 planting than either of the other communities (both
approximately 0.5% cover) of that planting. Cover in the
1999 planting was lowest in the annual community
(<0.025%) with cover in the seeded and shrub
communities similar to each other (approximately 0.5
%). Cover was highest in the soil treatments of all 3
communities in the 1999 planting (MANOVA:
community by treatment by planting F8, 204 = 3.281, P
<0.01).
At the last data collection of the 1999 planting in
2005, cover was highest in the annual community (18.5
 2.0 %), followed by the seeded (1.2  0.4%), with
almost no cover in the shrub community (0.005 
0.003%) (MANOVA: planting by community interaction
F2,240 = 17.260, P <0.001). Cover was highest in the soil
treatments (10.12.3%) followed by the fire treatment (7.1  2.1%), defoliation treatment (6.2  1.7%),
control (5.27  1.6), and ATV (4.3  1.7%) (MANOVA:
treatment F4,240=2.767, P <0.05).
Density (#/m2)
358 Int. Res. J. Agric. Sci. Soil Sci.
Figure 3. The effect of 4 disturbance treatments over time on
forage kochia density planted in 1999 in the annual community, the
seeded community, and the shrub community at Dugway Proving
Ground, Utah. Repeated measures ANOVA: F24, 306 = 1.630, p
<0.05. Bars represent standard error.
Sullivan et al. 359
DISCUSSION
plants reduces its survival and growth.
The invasive potential of an exotic plant species
depends on its biological and ecological attributes, as
well as the biological and ecological characteristics of
the resident natives and the plant community as a
whole (Sakai et al., 2001). Abiotic factors including soil,
topography and climate also have determining influence
(Hobbs and Huenneke, 1992). Our research involved 3
sites with 3 different and important plant communities
commonly found in the Intermountain West. Although it
was not replicated in space, thus limiting the
applicability of the results to the study site, our results
confirm trends seen in similar research.
Disturbance
Plant Community
The necessary resources for emergence and
establishment existed in all 3 plant communities in our
study regardless of disturbance. Concerning forage
kochia density over time, our results suggest that the
plant community in which it was seeded is a factor;
forage kochia density increased in the annual
community, and decreased in the seeded and shrub
communities regardless of disturbance treatment.
These results support other studies showing that forage
kochia out-competes annuals including cheatgrass,
medusahead rye and halogeton (McArthur et al., 1990,
Monsen and Turnipseed, 1990, Stevens and McArthur,
1990) and is out-competed by established crested
wheatgrass plants (Provenza and Richards 1984,
Stevens 1992). Although it has been shown that in
certain conditions forage kochia can establish among
both annual and perennial competitors (Keller and
Bleak, 1974; Van Epps and McKell, 1983, Stevens et al.
1985, Romo and Haferkamp 1987), it appears to be
most successful with little competition from established
perennial species (Stevens et al., 1984).
This competitive pattern may relate to the timing of
resource availability (Smith and Knapp 1999, With
2002, Walker et al., 2005). One of the most limiting
resources in desert ecosystems is water (Noy-Meir,
1973). Cheatgrass, the annual community dominant,
completes its life-cycle by mid-summer (Hulbert, 1955),
which reduces competition for resources such as soil
moisture late in the growing season when drought sets
in. This temporal offset creates a reduction in
competition that allows forage kochia additional
resources for growth throughout late summer. In
contrast, the seeded and shrub communities are
dominated by perennial species, which continue to
require water and other resources throughout the
growing season (Stevens, 1992). It appears that if a
forage kochia plant can survive through the initial
competition with cheatgrass it will persist and
reproduce, while continued competition with perennial
Variations at the microsite level likely influenced our
short-term results regarding the disturbance treatments.
For example, the only pre-seeding disturbance that
resulted in higher emergence, establishment and
density than the control was the soil treatment in the
1999 plots. The base of the overturned soil appeared to
create a favorable microsite for forage kochia; seedlings
were most often found around the base of the soil
disturbances rather than on top of or in the spaces
between. In addition, although precipitation in 1999 was
above average during January and April, it was scarce
February-March (Fig. 1), the time of most forage kochia
germination (Haferkamp et al., 1990, Stevens and
McArthur, 1990). When precipitation did fall during the
critical months, it pooled at the base of the soil
disturbances, where it may have increased available
soil moisture (e.g. Boeken and Shachak, 1994). In
addition, the 1999 planting was 18 days later than the
1998 planting which may have altered the soil
temperature and the degree-day accumulation
influencing germination and seedling growth. In looking
this closely at the microsite conditions, it is important to
note that this research included only one site and one
accession of forage kochia. Forage kochia has a high
degree of ecological plasticity (Young et al. 1981,
Krylova 1988) as well as genetic variation between
accessions (McArthur et al., 1996). Further research
with a variety of ecological sites and forage kochia
accessions is needed before results can be considered
conclusive on the species as a whole and the
environments in which it is found.
Overall, our disturbance treatments had little impact
on long-term forage kochia density and cover in these 3
plant communities. We tested different disturbance
agents applied at varying levels of intensity but all were
limited to a single disturbance event occurring before
the seeding took place. In practice, disturbance occurs
at a variety of temporal and spatial scales, and their
effects can vary depending on the timing, frequency,
and the extent of the disturbance regimes (Hobbs and
Huenneke, 1992; Sakai et al., 2001; Anderson and
Frank, 2003). It is likely that the treatments in this study
would have had a different effect if they had occurred at
a different time during the growing season, if they had
been applied in communities where forage kochia was
already established, or if treatments were repeated. In
addition, larger scale disturbances may have had a
different effect, particularly in the perennial communities
where lateral roots from adjacent unaffected plants may
have been in the disturbed plots (Abbott et al., 1991),
competing for below ground resources with forage
kochia in those disturbances.
360 Int. Res. J. Agric. Sci. Soil Sci.
ACKNOWLEDGEMENTS
Research was funded by USDOD and Brigham Young
University.
The authors would like to thank N. Bryan, R. Cox, C.
Horman, B. Jessop, M. Judy, R. Lucas, J. Scott, and D.
Smith their help with data collection. We would also like
to thank N. Cordeiro, A. Golubski, H.F. Howe, B.D.
Jessop, R.L. Johnson, M. Jorge, G. Nunez, and B.
Zorn-Arnold for helpful comments on earlier versions of
the manuscript.
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