St. Cloud State University
theRepository at St. Cloud State
Culminating Projects in Biology
Department of Biology
12-2011
The application of successional theory-based
management to Minnesota prairie sites degraded
by invasive plant species
Jamie R. Hanson
Saint Cloud State University, [email protected]
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THE APPLICATION OF SUCCESSIONAL THEORY-BASED
MANAGEMENT TO MINNESOTA PRAIRIE SITES
DEGRADED BY INVASIVE PLANT SPECIES
by
Jamie R. Hanson
B.S., St. Cloud State University, 2011
A Thesis
Submitted to the Graduate Faculty
of
St. Cloud State University
in Partial Fulfillment of the Requirements
for the Degree
Master of Science
St. Cloud, Minnesota
December, 2011
This thesis submitted by Jamie R. Hanson in partial fulfillment of the
requirements for the Degree of Master of Science at St. Cloud State University is
hereby approved by the final evaluation committee.
______________________________
Chairperson
______________________________
______________________________
________________________
Dean
School of Graduate Studies
THE APPLICATION OF SUCCESSIONAL THEORY-BASED
MANAGEMENT TO MINNESOTA PRAIRIE SITES
DEGRADED BY INVASIVE PLANT SPECIES
Jamie R. Hanson
A thesis project at Camp Ripley Army National Guard Training Site will
address the effectiveness of directing succession as a means of restoring areas
dominated by perennial terrestrial invasive species: Common Tansy (Tanacetum
vulgare) and Spotted Knapweed, (Centaurea stoebe ssp. micranthos). The purpose of
this project is to design and implement an experiment that will test different
combinations of treatments that alter the three factors of site availability, species
availability, and species performance, as defined by Pickett et al. (1987) and Sheley et
al. (2003). Altering these three factors is done with the goal of restoring perennial
invasive-species-dominated areas into a native plant community. My experimental
objective is to determine if succession-based management strategies are an appropriate
methodology for the restoration of Minnesota prairie ecosystems that are impacted by
invasive species, as it has been shown that invasive species can severely degrade
ecosystems. The research question further involves determining which practices
within this framework of succession are most effective in restoring Minnesota prairie
ecosystems that are degraded by the presence of these invasive plant species. This
experiment took place in spring 2010 through fall 2011 and incorporated site
manipulation of four seedbed preparations, two cover crop types, and two seed
dispersal methods. The addition of a fourth factor involved the application of a
selective herbicide, Milestone, to half of each plot. Statistical analysis determined that
by the end of data collection in August 2011, all levels from the first three factors in
the experimental design did not significantly reduce either invasive species. The
application of the fourth factor did significantly reduce both invasive species’ mean
percent cover. However, a negative consequence of this selective herbicide is
reduction in species richness in plots and increase in non-native grass cover. It is
iii
recommended, due to the nature of succession, continued monitoring, data collection,
and analysis occur on experimental sites.
_________________
Month
Year
Approved by Research Committee:
_________________________________
Jorge Arriagada
Chairperson
iv
ACKNOWLEDGMENTS
I would like to thank my advisor, Dr. Jorge Arriagada for his support and
assistance through the many trials and tribulations that accompanied this thesis
project. Previously known as my field assistant, and now a graduate student herself;
Kayla Malone made the execution of my experimental design possible. I cannot thank
Kayla enough for her innumerable hours spent on my project. I also thank my
committee members Dr. Marco Restani, Dr. Stephen Saupe, and Dr. Michner Bender.
The members of the Environmental Office and Department of Public Works at Camp
Ripley, Linda Donnay and others in the Office of Sponsored Programs were constant
supporters of this experiment, and for that I thank them immensely. Chen Zhu in the
Statistical Consulting Center and Dr. Jody Illies at Saint Cloud State University were
invaluable assets to the statistical analyses contained within this thesis. Last, but not
least, I thank my family and especially my friends for being with me on this two and a
half year journey.
v
TABLE OF CONTENTS
Page
LIST OF TABLES .................................................................................................
viii
LIST OF FIGURES ................................................................................................
xi
Chapter
1.
2.
3.
INTRODUCTION ......................................................................................
1
Invasive Species ...................................................................................
1
Common Tansy and Spotted Knapweed ..............................................
6
Ecological Succession ..........................................................................
13
Objectives .............................................................................................
19
METHODS .................................................................................................
22
Study Site ..............................................................................................
22
Experimentation Design .......................................................................
26
Procedures ............................................................................................
28
RESULTS ...................................................................................................
36
Initial Data Collection—2010 ..............................................................
36
Senescent Stand Data Collection—2011 ...............................................
37
Emergent Stand Data Collection—2011 ..............................................
40
Post-Milestone Application Data Collection—2011 ............................
42
vi
Chapter
Page
2011 Vegetation Surveys ......................................................................
45
Statistical Analyses ...............................................................................
56
Boxplot Figures ....................................................................................
66
DISCUSSION .............................................................................................
73
REFERENCES .......................................................................................................
77
APPENDIX ............................................................................................................
89
4.
vii
LIST OF TABLES
Table
Page
1.
Ups13 Southern Dry Prairie native plant community as defined by the
DNR Ecological Classification System 2005 .......................................
24
2.
UTM GPS Point Location of Blocks at Camp Ripley, MN .......................
28
3.
Timeline of events in 2010 .........................................................................
34
4.
Timeline of events in 2011 .........................................................................
35
5.
A random number generator was used to determine the number of
steps walked within the block to visually estimate senescent
stand invasive species percent cover in April 2010 of a meter
sized area at that point with a total of 16 points per block ...................
37
6.
April 2011 senescent stand mean percent cover of spotted knapweed .......
39
7.
April 2011 senescent stand mean percent cover of common tansy ............
39
8.
A block mean of visual estimates of senescent stand invasion species
percent cover in April 2011 of each 10 by 20 meter plot .....................
40
9.
May 2011 emergent stand mean percent cover of spotted knapweed ........
41
10.
May 2011 emergent stand mean percent cover of common tansy .............
41
11.
A block mean of visual estimates of emergent stand invasive species
percent cover in May 2011 of each 10 by 20 meter plot ......................
42
12.
July 2011 Post-selective-herbicide treatment mean percent cover of
spotted knapweed .................................................................................
44
13.
July 2011 Post-selective-herbicide treatment mean percent cover of
common tansy .......................................................................................
44
viii
Table
14.
Page
A block mean of visual estimates of post-selective-herbicide treatment
invasive species percent cover in July 2011 of each 10 by 20
meter plot ..............................................................................................
45
2011 Species Richness per half-plot (# spp.) with 1m squared
quadrat sampling frame randomly placed at least one meter
from buffer zone ...................................................................................
47
16.
Species richness per half-plot (# spp.) with 1m squared quadrat
sampling frame randomly placed at least one meter from buffer zone
48
17.
Forb and tree surveys in June and August 2010 .........................................
49
18.
Forb and tree surveys in August 2011 ........................................................
51
19.
Grass surveys in August 2010 ....................................................................
52
20.
Grass surveys in August 2011 ....................................................................
53
21.
Cover class mean values for every treatment of the four blocks in
spotted knapweed areas was determined by randomly placing
a 0.2 by 0.5 m Daubenmire frames in each half-plot ...........................
54
Cover class mean values for every treatment of the four block in
common tansy areas was determined by randomly placing a
0.2 by 0.5 m Daubenmire frames in each half-plot ..............................
55
23.
Common tansy independent samples t-test for species richness in
plot halves with and without a selective herbicide application ............
58
24.
Spotted knapweed independent samples t-test for species richness
in half-plots with and without a selective herbicide application ..........
59
25.
Univariate ANOVA for spotted knapweed areas with the BetweenSubjects factors of seedbed preparation (SP), cover crop (CC),
seeding method (SM), selective herbicide application (MS),
and block ..............................................................................................
59
26.
Univariate ANOVA for spotted knapweed ................................................
61
27.
Repeated Measures ANOVA for spotted knapweed areas with the
Within-Subjects Effects of time on mean percent cover ......................
62
15.
22.
ix
Table
Page
28.
Repeated Measures ANOVA for spotted knapweed ..................................
62
29.
Univariate ANOVA for common tansy area with the Between-Subjects
factors of seedbed preparation (SP), cover crop (CC), seeding
method (MS), selective herbicide application (MS), and block ...........
63
30.
Univariate ANOVA for common tansy ......................................................
65
31.
Repeated Measures ANOVA for common tansy areas with the
Within-Subjects Effects of time on mean percent cover ......................
65
32.
Repeated Measures ANOVA for common tansy .......................................
66
x
LIST OF FIGURES
Figure
1.
Page
Common tansy (Tanacetum vulgare) and spotted knapweed
(Centaureastoebe ssp. Micranthos) distribution as of
2010 at Camp Ripley ............................................................................
9
2.
The Pine Moraines and Outwash Plains, Hardwood Hills, and
Anoka Sand Plain subsections converge at Camp Ripley ....................
23
3.
A randomized complete block design (2x2x4) ...........................................
26
4.
Treatment assignments were determined by plots receiving a random
number between 1-16 ...........................................................................
27
5.
Spotted knapweed blocks’ mean percent cover measures for all
data sets ................................................................................................
67
6.
Spotted knapweed mean percent cover measures per data set ...................
68
7.
Spotted knapweed mean percent cover measures for plot halves within
blocks that received no selective herbicide versus those half-plots
that received a selective herbicide application .....................................
69
8.
Common tansy mean percent cover measures per block ............................
70
9.
Common tansy mean percent cover measures per data set ........................
71
10.
Common tansy mean percent cover measures for plot halves within
blocks that received no selective herbicide versus those halfplots that received a selective herbicide application ............................
72
xi
Chapter 1
INTRODUCTION
Invasive Species
Invasive species are non-native species that harm economic, environmental, or
human health (Executive Order 13112). These species are a threat to the ecological
health of areas around the world due to their capability of changing the biotic and
abiotic characteristics of their environment (Osborn, Wright, Walker, Cilimburg, &
Perkins, 2002).The term “invasive” has had many other names and definitions. Other
terms that have been used to describe a non-native harmful species include:
introduced, naturalized, exotic, alien, pests or weeds, and noxious. The term invasive
was specifically defined by Executive Order 13112 in 1999 to eliminate ambiguity
surrounding the word’s meaning. Other vocabulary previously used as synonyms of
“invasive” can still be useful. To be explicit, an introduced species is defined as any
species that has been moved via humans to an area that originally was inaccessible due
to some geographical barrier. An alien or exotic species are also “plant taxa in a given
area whose presence there is due to intentional or accidental introduction as a result of
human activity” (Richardson et al., 2000, p. 98). Alien and exotic species are generally
used as synonyms of introduced. A naturalized species is a species that that can
1
2
overcome the challenges of being transported into a new area and can survive on its
own. A naturalized species is not necessarily invasive, as it does not necessarily cause
harm. A weed is a plant species that “grow[s] in sites where they are not wanted and
which usually have detectable...effects” (Richardson et al., 2000, p. 98). “A noxious
weed is an undesirable plant species that is regulated in some way by law” (Sheley &
Petroff, 1999, p. 1). It is also important to note that native species are, in a specific
ecosystem, a species that historically occurred or currently occurs in that ecosystem
(Executive Order 13112, 1999, p. 6183).
Masters and Sheley describe invasive plant species as those species that
“reduce the capacity of ecosystems to provide goods and services required by society,
alter ecological processes, and can displace desirable species” (2001, p. 503). Until
the 20th century it was not extensively known that a non-native plant can become
harmful (invasive) if said plant has certain characteristics and is introduced into
certain conditions. It is now known that the spread of invasive plant species have vast
financial and ecological repercussions across the globe. According to Walker and
Smith (1997), entire ecological processes, such as fire regimes, can be altered by the
establishment and aggressive spread of a single non-native species. Invasive species
have been introduced and spread rapidly between areas over the past century due to
the exponential increase in human population and movements and the human
alteration of environments. Invasive plants species have established in the United
States via accidental and intentional introduction via human vectors (Morse, Kartesz,
3
& Kutner, 1995). Humans have introduced non-native plants for various purposes,
such as food, livestock forage, ornamental, medicinal, and erosion control.
In 1958, a manuscript concerning invasive species, and the negative impacts
they incur, was published, The Ecology of Invasions by Animals & Plants. In this text,
Charles Elton dubbed the impact of invasive species as “ecological explosions”. His
text described the potential dangers that non-native plants and animals pose to new
environments and also used case studies to illustrate the damage that had already been
done by these species (Elton, 1958). Invasion ecology has developed since Elton’s text
into a field of study of its own. In 2011, when one uses Google Scholar search engine
to look for articles on “invasive species,” over 64,000 items are returned. Every year,
more research is being conducted and the findings are illuminating the issue of
invasive species to the world. There is much work to be done, however, as the more
that we know about the methods and mechanisms by which invasive species function,
the better equipped we are to combat this threat.
The mechanisms by which plant species can change from being non-native to
being classified as invasive can be complex and multi-layered. Masters and Sheley
summarized various hypotheses about the contributing factors that lead to species
being invasive:
The absence of predator hypothesis states that invasive plants have an
advantage because they are introduced into new environments without natural
enemies from their native range. The greater reproductive potential hypothesis
indicates that invasive plants are more fecund than native species. The poorly
adapted native species hypothesis proposes that invasive plants exhibit a
greater tolerance to resource constraints than do native species. The chemical
change hypothesis suggests that invasive plants are better adapted to altered
4
chemical status of an invaded site. The balance of nature hypothesis is centered
on the concept that species-rich communities are more resistant to invasion
than species- poor communities. The empty-niche hypothesis contends that
invaded communities contain unoccupied niches ready for habitation by
invasive plants. The disturbance-produced gaps hypothesis suggests that some
level of disturbance is necessary to allow an invading species to gain a
foothold in a community. (2001, p. 504)
All or only some of these hypothetical contributions to what makes a species invasive
may be useful depending on the specific situation. Invasions can also have a scale or
varying measure of “success” in new environments. Rejmanek stated that invasion
success is dependent on the severity and kind of disturbance and propagule pressure
(1989). Hobbs and Huenneke proposed that the amount of time between disturbances
can also influence invader success (1992).
The process by which a species invades an ecosystem outside of its native
range has been organized into delineated phases, A-D, by Williamson (1996). These
four phases are (a) arrival and establishment, the beginning, (b) spread, the middle,
and (c) equilibrium and effects, the end of the invasion process. Phase (d) resembles
the implications of the invasion. In the first phase (a), a non-native species enters a
new area and it either succeeds or fails in establishment of a viable, potentially
permanent, group of individuals. In most cases, Williamson notes that the majority of
introductions are not successful and that propagule pressure is often a determinant of
success or failure. He also states that all ecosystems should be considered invasible
given the right circumstance. In phase (b), the population of viable individuals begins
to spread. This phase lends itself to being modeled better than the other phases. Spread
can occur in various directions in various speeds. The next phase, (c), involves an
5
introduced species reaching equilibrium. At this point, the population stops spreading.
It is noted that at this phase, most invaders will not have major consequences for the
ecosystem. When they do they are in the form of effects such as extinctions of native
species. At this point, evolution of the invader population and the native populations
can begin to be affected by the presence of the invader in the environment. The final
phase (d) addresses the implications of a successful invasion. These implications are
varied and often observable depending on the invaders’ impact (Williamson 1996).
The National Invasive Species Council and the Federal Interagency Committee
on Management of Noxious and Exotic Weeds estimated that as of 2001, 40.5 million
has of area in the United States are infested with harmful non-native plants (NISC,
2001). It was also estimated that this area will increase by 8 to 20% every year
(Westbrooks, 1998). In response to the reality that invasive plant species are both an
economic and ecological threat to the United States, an executive order was issued on
February 3, 1999 by President William Clinton to address the problem at the federal
level. This executive order mandates that it is imperative that each federal agency take
the following actions:
…prevent the introduction of invasive species; detect and respond rapidly to
and control populations of such species in a cost-effective and environmentally
sound manner; monitor invasive species populations accurately and reliably;
provide for restoration of native species and habitat conditions in ecosystems
that have been invaded; conduct research on invasive species and develop
technologies to prevent introduction and provide for environmentally sound
control of invasive species; and promote public education on invasive species
and the means to address them; and…not authorize, fund, or carry out actions
that it believes are likely to cause or promote the introduction or spread of
invasive species in the United States or elsewhere… (Executive Order 1311,
p. 6184)
6
Common Tansy and Spotted Knapweed
The Minnesota Department of Military Affairs is one of the federal agencies
that are required to be in compliance with this executive order. The Minnesota
Department of Military Affairs manages Camp Ripley Army National Guard Training
Site. Camp Ripley Army National Guard Training Site (Hereafter Camp Ripley) is
located in Morrison County and is the primary study site for this thesis project.
Eighteen terrestrial invasive plant species have been identified at Camp Ripley
including two species that this project will be addressing: Common tansy (Tanacetum
vulgare), and spotted knapweed (Centaurea maculosa) (St. Cloud State University
[SCSU], 2008). These two species are of special concern due to their highly
aggressive and opportunistic nature and large distributions at Camp Ripley.
Common tansy (Tanacetum vulgare Linnaeus) is an aggressive perennial plant
present at Camp Ripley. It is a member of the Asteraceae family, native to Europe.
This plant was first introduced as an ornamental and for medicinal purposes (Colorado
Weed Management Association [CWMA], 2004; United States Department of
Agriculture [USDA], 2004). It has been classified as a Noxious or Secondary Noxious
Weed in some states due to its potential to reduce forage for livestock, wildlife habitat,
and species diversity. These states include Minnesota, Colorado, Montana,
Washington, and Wyoming (USDA, 2010). Common tansy is capable of producing
50,000 seeds per plant (Royer & Dickinson, 1999; Whitson, 2000). It can also
reproduce asexually, via vegetative re-growth of the rhizomes though it primarily
relies on seed production for its spread (Jacobs, 2008; Prach & Wade, 1992).
7
The scientific taxonomy of common tansy began with Carl Linnaeus who
worked for the Dutch merchant and plant enthusiast George Clifford from 1735-1737.
George Clifford founded a herbarium with an extensive collection now housed in the
Natural History Museum in London, UK. The lectotype for common tansy can be
found in this collection. Linnaeus published a brief Latin species account of
Tanacetum vulgare in Species plantarum vol. 2 in 1753.
The USDA Forest Service offers an English description of the characteristics
of Common Tansy:
Common tansy is a robust perennial with erect stems that may reach 7 feet (2
m) tall. Coarse stems generally branch only at the top and are somewhat
woody at the base. Stems may grow singly or in clusters and are lined with
alternate leaves. When crushed, leaves produce a “rank” smell. Leaves are
finely dissected and toothed. They measure 2 to 12 inches (6-30 cm) long and
are generally half as wide. Common tansy flower heads are comprised of
daisy-like disk florets and measure up to 0.5 inch (1.2 cm) wide. Within the
flower head there may be as many as 100 individual florets. Florets are perfect
except for the outermost, which are pistillate. Generally florets are without ray
flowers, but in some cases, reduced ray flowers are present. Flower heads are
densely clustered in flat-topped terminal inflorescences. Sources report that
common tansy may produce more than 8 flower heads/stem and between 20
and 200 flower heads/plant. Common tansy produces achenes that measure 1
to 1.8 mm long; the pappus, if present, is a reduced 5-toothed crown. (Gucker,
2009, p. 3)
Common tansy quickly infests disturbed sites and displaces native vegetation.
It is tolerant of most soil types and prefers areas that are exposed to full sun.
Roadsides, stream banks, pastures, and open disturbed areas are likely areas of
infestation (Whitson, 2000). Tansy plants can emerge from rhizome extensions in the
fall, but most stems emerge in mid-spring. Upon emergence, quick growth results in
plants over a meter tall in June. Flowers form in June with seeds dropping in late
8
summer and early fall. Seeds have highest germination rates after a period of
stratification (Jacobs, 2008). Common tansy is an ecological threat due to its ability to
out-compete native grass species and reduce forage for wildlife and some livestock
(LeCain & Sheley, 2006). The current distribution (point locations only) of this plant
at Camp Ripley can be seen in Figure 1.
Current control methods include prescribed burns combined with herbicides
(Jacobs, 2008), mechanical control by means of hand-pulling (CWMA, 2009) and
mowing at appropriate times to prevent seeds from establishing (Lackschewitz, 1991),
and grazing by sheep or goats (Elpel, 2009).
Spotted knapweed (Centaurea stoebe ssp. micranthos (Gugler) Hayek) is
another aggressive terrestrial invader which has also posed a problem at Camp Ripley.
Historically, this plant was introduced to this country either as a contaminant of alfalfa
seed from Asia, specifically Turkmenistan, or as a contaminant of alfalfa seed from
Germany. The history of the taxonomy of spotted knapweed is incredibly complex. As
early as 1601, Carolus Clusius wrote about a species that may have been spotted
knapweed (Ochsmann, 2001). Carl Linnaeus describes this species in 1753 in his
Species Plantarum (Linnaeus, 1753). Through molecular and ecological data, obtained
and then related by Jörg Ochsmann, the final designation of Centaurea stoebe ssp.
micranthos (Gugler) Hayek was accepted for spotted knapweed (2001). No type has
been designated for Centaurea stoebe L. (Ochsmann, 2001).
9
Figure 1. Common tansy (Tanacetum vulgare) and spotted knapweed
(Centaureastoebe ssp. micranthos) distribution as of 2010 at Camp Ripley. Point
locations are shown in this figure, which only show a location of a population,
but do not relate information about size of individual infestations, which are, in
some cases, greater than a ha in area.
10
No halotype was designated within the herbaria used by Linnaeus. An isotype,
forCentaurea stoebe ssp. micranthos (Gugler) Hayek is cited as “C. Baenitz, Herb.
Europ.Sine No. [...] (Gugler, 1907, p. 169).
In Ochsmann’s conclusion, he states the importance of correctly identifying the
taxonomy of the invasive subspecies of spotted knapweed:
Even when the taxonomic view of the author is not accepted and Centaurea
maculosa Lam. is used instead of C. stoebe L. for spotted knapweed, it is
important to recognize that different (infraspecific) taxa of spotted knapweed
exist and that only one of them (subsp. micranthos) was introduced to North
America. Only with knowledge of the two subspeciesof C. stoebe it is possible
to understand the biology and ecology of spotted knapweed and to improve the
methods of control in North America. (2001, p. 39)
This perennial species has the capacity to produce over a thousand seeds per
plant. These seeds have long-lasting viability in the soil and can produce new plants
five years or more after introduction to the seedbed (Lym & Zollinger, 1992). Due to
its persistence in the landscape and its allelopathic properties, this species has proven
to be difficult to manage. In its mature stage spotted knapweed is unpalatable to
wildlife and some livestock (Harris & Cranston, 1979).
The description of the North American Invasive variety as reviewed in
Ochsmann of Centaurea stoebe ssp. micranthos (Gugler) Hayek is as follows:
Perennial (up to 9 years), polycarpic; usually many-stemmed, erect, ca 40-150
(-200) cm high; stem paniculate branched, with relatively long branches; plants
lanate; rosette leaves one- to many-times pinnatifid to pinnatisect with narrow
sections, upper leaves mostly undivided; capitula single at the ends of the
branches, 5-8 mm wide, narrow ovate to ovate; phyllary appendages often
tinged with dark violet, sometimes ± lanate, black, triangular, acute, ciliate,
with 4-7 cilia per side, each 1-2 mm long; flowers purple, ray florets present,
flowering VI-IX; achenes ca 3-3.5 (-4) mm long; pappusca (0.2-) 1-2.5 mm.
(2001, p. 38)
11
Spotted knapweed quickly establishes itself in areas that have been disturbed,
and is even capable of occurring in stable plant communities if a source population is
nearby (Sheley, Jacobs, & Carpinelli, 1998). This plant prefers dry soils and sunny
conditions. It has been known to occur at elevations between 580 to over 3000 meters
and in areas with between 200 to 2000 millimeters of precipitation (Lacey, Lacey, &
Faye, 1992). Roadsides and open disturbed areas are most susceptible to invasion by
spotted knapweed (Forcella & Harvey, 1983). These plants’ seeds germinate in both
fall and early spring between April and June. This early germination time is a factor
that contributes toward this species’ invasiveness. Seeds are shed from mature plants
between August and September (Jacobs & Sheley, 1998). It is considered an
ecological threat mainly due to the arresting capacity it has on succession of native
plant communities (Tyser & Key, 1988). Also, once an area has an established
population, it is then a source of invasion of adjacent ecologically stable areas (Tyser
& Key, 1988). Spotted knapweed has been shown to have increased erosion on
invaded sites compared to those areas that are dominated by native plants (Lacey,
Marlow, & Lane, 1989). Overall, spotted knapweed is an economic and ecological
concern due to its capacity to reduce forage for livestock (Watson & Renney, 1974),
reduce native plant community biodiversity (Tyser, 1990), cause a reduction in soil
fertility and an increase in soil runoff (Lacey et al., 1989), and has negative effects on
rare forbs and wildlife (Bedunah & Carpenter, 1989; Lesica & Stephen, 1996). The
current distribution of this invasive species at Camp Ripley is shown in Figure 1.
Current control methods for spotted knapweed include prescribed fire followed by
12
herbicide treatment (Sheley,Jacobx, & Carpinelli, 1999), and other integrated weed
management practices such as combining chemical, cultural, and biological controls
(Sheley et al., 1996b).
These two perennial invasive species have negatively impacted the ecological
health of Camp Ripley. Their presence on this military training site threatens to serve
as a source population that could eventually have economic impacts for adjacent areas
in Minnesota. To be in compliance with Executive Order 13112, steps have been taken
to control and manage these invasive populations on this training site. A partnership
has been established between Saint Cloud State University and Camp Ripley. Multiple
participants in this operation exist, including the MN Department of Military Affairs,
The Nature Conservancy, Camp Ripley Environmental Office, and the Saint Cloud
State Biology Department. Previous efforts have involved mapping distributions and
predicting future spread of these species by Jill Babski in 2004, establishing herbicide
control on plots within the site by Joseph Eisterhold in 2008, and evaluating chemical
and fire control of one of these species, common tansy, by Joseph Carlyon in 2009.
Recommendations have been made on how to control these invasive species and
prevent introductions. However, this project concerns itself on how best to restore
these invasive dominated areas into an ecologically sound native plant community.
Restoring these areas back to a native plant community is difficult due to the
factors that make these plants invasive. Spotted knapweed and common tansy have
high seed production and these seeds are viable for years in the soil (Biesboer &
Koukkari, 1992; Davis & Fay, 1989). These plants out-compete natives and can
13
change characteristics of the soil through root system development and by changing
the nutrient cycles of the area (Olson & Blicker, 2001; Harvey & Nowierski, 1989;
Marler, Zabinski, Wojtowicz, & Callaway, 1999). Ridding areas of these plants has
proven to be very difficult as both exhibits some form of asexual reproduction via
their rhizomes in conjunction with seed production (Raju, Steeves, & Clupland, 1963;
Sheley, Jacobs & Lucas, 2001). These plants have also thought to inhibit other species
from thriving by method of allelopathy (Callaway & Aschehoug 2001). Early
germination rates and fast growth early in the growing season gives these species a
competitive edge versus the native plant community (Eddleman & Romo, 1988).
Ecological Succession
Methods for long-term control of these invasive species have been proposed
that involve the use of the ecological principle of succession (Pickett, Collins, &
Armesto, 1987; Sheley, Mangold, & Anderson, 2006). Succession has been observed
for hundreds of years by various naturalists. It was not until the late 19th century that
scientists began actively exploring the concept, however. It is a difficult concept to
study, as the complexity of abiotic and biotic interactions has led to many proposed
patterns and mechanisms.
Pickett et al. describes succession as,
…one of the oldest of ecology’s major theories...it embodies the
pervasive and fundamental idea that ecological systems are dynamic as a result
of both internal and external forces... it has evolved through shifts in paradigm,
growth of long-term studies, and examination of contrasting systems. (2008, p.
338)
14
A pattern described by one researcher, or a mechanism described by another,
had not proven to be applicable as a general theory on succession until late in the 20th
century.
Henry Cowles in 1899 was one of the first researchers to describe what is now
referred to as primary plant succession. He studied vegetation composition and change
over time on sand dunes (Cowles, 1899).
Frederic Clements in 1916 proposed a deterministic, highly predictable view
on the causes, stages, and sequences of succession. He proposed the idea that
succession has an orderly process with an endpoint, resulting in a climax community
(Clements, 1916). This became the traditional model of succession until the 1950s.
Henry Gleason was critical of the Clementsian model of succession. From
1917 onwards, Gleason proposed an individualistic model of succession which
investigated the complex and variable interactions between environments, the species
within it, and disturbances that affect it. He was a proponent for a less-predictable
pattern of succession than that stated by Clements (Gleason, 1917).
Many researchers proposed further additions to the deterministic or
individualistic views on succession. Frank Egler described succession, both primary
and secondary stages, as a gradual process that he dubbed “Relay Floristics and Initial
Floristic Composition.” Relay floristics refers to the
...successive appearance and disappearance of groups of species. Each group of
species invades the site at a certain stage of development... making conditions
unsuited for themselves, but suited for invasion by the next group. And so
...predominance is relayed... from one floristic group to another, until some
relatively stable end-stage is attained... The second principle is called Initial
15
Floristic Composition, and refers to that element which invades or has invaded
at the time of abandonment. Following abandonment, there is a progressive
development, with the forbs and grasses assuming predominance first, and the
trees last. (Egler, 1954, p. 414)
Robert MacArthur defined r and K selection, which enhanced the
understanding of biotic influences on succession. “r” species were early successional
species that had properties such as elevated reproductive, higher rates of dispersal, and
increased survival of severe abiotic and biotic conditions. “K” species are found in late
stages of succession. These species have properties such as lower rates of
reproduction, longer lifetimes, and greater environment regulation (MacArthur, 1962).
Eugene Odum explained predictable deviations between early and late
succession in 1969. He stated that “early successional systems tend to have smaller
plant biomass, shorter plant longevity, faster rates of soil nutrient consumption ...
higher rates of net primary productivity, lower stability and lower diversity than late
successional systems” (Odum, 1969).
In 1977, Joseph Connell and Ralph Slatyer summarized various models of
succession (Connell & Slayter, 1977):
Connell and Slatyer propose three models, of which the first (facilitation) is the
classical explanation most often invoked in the past, while the other two
(tolerance and inhibition) may be equally important but have frequently been
overlooked. The essential feature of facilitation succession, in contrast with
either the tolerance or inhibition models, is that changes in the abiotic
environment are imposed by the developing plantcommunity. Thus, the entry
and growth of the later species depends on earlier species preparing the
ground. The tolerance model suggests that a predictable sequence is produced
because different species have different strategies for exploiting resources.
Later species are able to tolerate lower resource levels due to competition and
can grow to maturity in the presence of early species, eventually out competing
them. The inhibition model applies when all species resist invasions of
16
competitors. Later species gradually accumulate by replacing early individuals
when they die. (as cited in Pidwirny, 2006, p. 5)
The Resource Ratio Hypothesis was proposed by David Tilman in 1985. This
hypothesis models changes in plant communities derived from the assumption that
succession is determined by exchanges between competition for nutrients early on in
succession, and light acquisition late in succession (Emery, 2010).
Pickett et al. proposed that Connell and Slatyer’s statements on succession
were, in some cases, contradictory or empirically unobservable. Picket et al. stated that
the Connell and Slatyer model of succession had testable limits. To make clear certain
concepts in succession, Pickett et al. (1987) explored the causes of succession: “site
availability” or disturbance, “species availability” or colonization, and “species
performance”. Furthermore, Pickett et al. concretely defined several terms surrounding
succession:
A successional pathway is the temporal pattern of vegetation change. It can
show the change in community types with time, the series of system states, or
describe the increase and decrease of particular species populations. A
mechanism of succession is an interaction that contributes to successional
change. A model of succession is a conceptual construct to explain
successional pathways by combining various mechanisms and specifying the
relationship among the mechanisms and the various “stages” of the pathway.
(Pickett et al., 1987, p. 338)
Pickett et al. (1987) described succession as “a process of (1) individual replacement
and (2) a change in performance of individuals” (p. 347). The three factors of site
availability, species availability, and species performance can be illustrated by
contributing processes as was explored by Sheley, Svejcar, & Maxwell (1996a). In the
case of site availability a contributing process would be a disturbance. Species
17
availability is determined by propagule pressure and dispersal. Species performance
has many contributors such as available resources, life histories, and abiotic
conditions. Sheley et al. (1996a) proposed that disturbance can be designed, in that if
management includes activities that create or restrict site availability, the end result
can minimize continuous and costly management. Disturbances can be created or
restricted with management activities such as prescribed fire, cultivation, and
herbicides. White and Pickett (1985) define disturbance as “a relatively discrete event
in time that disrupts ecosystem, community, or population structure and changes the
resources, substrate availability, or physical environment” (p. 7). Colonization can
also be managed by altering the availability or establishment of plant species in a
specific area. Seed banks or propagule pools can be addressed by either introducing
seed, or by restricting entry of seeds. Management of a site for optimizing germination
of desirable species, while restricting the germination of undesirable species such as
those that are invasive should be a main focus of any site restoration. Controlling
species performance involves attempting to direct the growth and reproduction of
plant species in the management area. Introducing predation that restricts the growth
and reproduction of undesirable species (biological control), removing certain plant
species, and planting competitive plant species are all ways of addressing species
performance (Sheley et al., 1996a). According to Sheley et al. (2006), “The potential
of this successional theory to guide the development and implementation of effective
restoration and invasive plant management is substantial, but largely untested” (p.
366).
18
This project will test ecology based methods of restoration in areas dominated
by spotted knapweed and common tansy. Ultimately, the goal of the project would be
to restore these areas back to a pre-disturbance native plant community using the
approach of successional management. The Society for Ecological Restoration defines
restoration as “the intentional alteration of a site to establish a defined indigenous,
historic ecosystem” (Aronson, Floret, Le Floc’h, Ovalle, & Pontanier, 1993, p. 8).
An “assisted succession” method of restoration was conducted by Cox and
Anderson (2004) in areas infested with an annual invasive grass. Assisted succession
is the preliminary introduction of competitive, non-native grasses followed by a later
seeding of native species (Jones, 1997). Cox and Anderson (2004) attempted to restore
a native grassland through the following procedure; Seeding an introduced grass in the
infested areas, performing various seedbed preparations including herbicide
application, mowing, and tilling, and lastly, seeding the desired native plants. This
technique of using a cover crop or bridging species in the restoration process will be
implemented in this project.Cover crops are short-lived species that are seeded with
the focal crop to facilitate its establishment (Hartwig & Ammon 2002). However, in
this project, a native species will be used. Canada wild rye (Elymus canadensis) is a
native cool-season graminoid that is found in sand prairies in Minnesota (Wanek &
Burgess, 1965). Canada Wild Rye was chosen because it is known to increase habitat
stability and is adapted to a wide variety of soils (Atkins & Smith, 1967).
Sheley et al. (2006) conducted an experiment with a factorial design in 2006
that tested multiple herbicides, seeding methods, and seeding rates. Sheley et al.
19
intended to influence species performance, disturbance, and colonization by
manipulating the above variables (2006). “The experimental goalwas to investigate the
initial response of vegetation to various restoration strategies applied within the
context of successional management on rangeland dominated by invasive weeds
[Centaurea maculosa and Potentilla recta]” (Sheley et al, 2006, p. 366). The results of
Sheley suggested that:
in most cases, integrating treatments that addressed multiple causes of
succession favored a desired plant community. Thus, we accomplished our
goal of using successional managementto direct plant communities toward
native desired species, but the treatments used did notimprove species richness.
Since naturally occurring native forbs did not respond favorably toany
treatment combination, ecological restoration using successional management
may best bethought of as an iterative procedure where various components and
processes of the system aremethodically repaired or replaced over time. (2006,
p. 365)
Other components/processes will be introduced in this project involving
different seedbed preparation methods (Mowing versus mowing with herbicide
application versus mowing with herbicide application with tilling) and seed dispersal
methods (hand broadcasting versus drill seeding). This project began in April 2010
and data collection occurred for two consecutive growing seasons.
Objectives
The objective of this thesis project is to use a successional management
method of restoring perennial invasive-species-dominated areas into a native plant
community. This method incorporates various treatments including seedbed
preparations, cover crop implementation, and seed dispersal methods. These
20
treatments serve as the alterations to the successional factors of site availability,
species availability, and species performance. By altering these factors, I intend to
direct succession so that native plant species can compete with and pervade through
the arrest caused by spotted knapweed and common tansy in the current vegetation
system. The implementation of Canada wild rye into sites will serve as the alteration
to “species availability” and also as an alteration to “species performance”, as this
cover crop can both compete with the target invasive species and serve as a bridge
species for the desired native prairie plant community. I hypothesize that by
introducing a competitive cover crop immediately upon intentional disturbance of
these invaded areas, followed by the seeding of native grasses, a decrease in target
invasive species’ percent cover measures will occur. The addition of nine native grass
species via two dispersal methods, hand-broadcasting and drill-seeding, will also
influence “species availability,” due to the introduction of previously absent
propagules and is predicted to also impact “species performance,” due to the
competitive pressure introduced once these native propagules germinate. I hypothesize
that drill seeding will be the most effective means of establishing native grasses in the
seedbed. Seedbed preparations of Mowing versus mowing with herbicide application
versus mowing with herbicide application with tilling will act as the manipulative
element in altering “site availability” as I believe that these preparations will increase
the availability or openness of sites that were previously occupied by the target
invasive species. I hypothesize that the most successful decrease in invasive plant
21
percent cover will occur on sites that are mowed and then sprayed with a non-selective
herbicide.
Chapter 2
METHODS
Study Site
Camp Ripley (15000 Hwy 15, Little Falls, MN 56345, USA) is a 21,500 ha
facility that is located along the forest transition zone in central Minnesota (lat. 46.2N,
long. 94.3W), positioned along the divide between the Laurentian Mixed Forest
province, and the Eastern Broadleaf Forest Province. Three subsections converge on
Camp Ripley: Hardwood Hills, Anoka Sand Plain, and Pine Moraines and Outwash
Plains. (Figure 2) (Minnesota DNR, 2010). The Crow Wing River and Mississippi
River border Camp Ripley to the north and east. Fifty-five percent of the installation is
dryland forest habitat type and the remaining 45% is open grassland, brush land, or
wetland habitat (Division of Ecological Resources Minnesota Department of Natural
Resources for the Minnesota Army National Guard, 2008). Over 600 plant species
have been identified at Camp Ripley along with over 300 animal species. Spotted
knapweed and common tansy are present at Camp Ripley in areas that are open
grassland or oak savannah ecotypes. There are three soil type associations in grassland
areas at Camp Ripley: Hubbard-Duelm-Isan, Mahtomedi-Menahga, and CushingMahtomedi-Demontreville associations.
22
23
Figure 2. The Pine Moraines and Outwash Plains, Hardwood Hills, and Anoka Sand
Plain subsections converge at Camp Ripley. Subsections defined by the MN
Department of Natural Resources.
All three of these soil associations are characterized by well to excessively
drained, sandy, or loamy, slightly acidic soil (Almendinger, Hanson, & Jordan, 2000;
Reetz & Camp Ripley Environmental Office, 1998). The native plant community that
is being restored in these areas is classified as Ups13 Upland Prairie System Southern
Dry Prairie as defined by the Field Guide to the Native Plant Communities of
Minnesota: The Eastern Broadleaf Forest Province (Minnesota Department of Natural
Resources [MN DNR], 2005). This community is defined as:
24
Grass-dominated herbaceous communities on level to steeply sloping sites with
droughty soils. Moderate growing-season moisture deficits occur most years,
and severe moisture deficits are frequent, especially during periodic regional
droughts. Historically, fires probably occurred every few years. (MN DNR,
2005, p. 240)
Vegetation found in this native plant community is listed in Table 1.
Precipitation from April to August 2010 was 22.81 cm. Precipitation from
April to August 2011 was 40.46 cm. The Average rainfall from April to August over a
25 year span is 42.8 cm.
Table 1. UPs13 Southern Dry Prairie native plant community as defined by the DNR
Ecological Classification System 2005
Forbs, Ferns, and Fern Allies
Grasses and Sedges
Schizachyrium
Little bluestem
scoparium
Bouteloua
Side-oats grama
curtipendula
Andropogongerard
Big bluestem
ii
Sporobolusheterol
Prairie dropseed
epis
Purple prairie clover
Dalea purpurea
Gray goldenrod
Solidago nemoralis
Silky aster
Aster sericeus
Heath aster
Aster ericoldes
Stiff goldenrod
Long-headed
thimbleweed
Bearded birdfoot
violet
Solidago rigida
Anemone
cylindrica
Porcupine grass
Viola pedatifida
Indian grass
Rough blazing star
Liatrisaspera
June grass
Stipaspartea
Muhlenbergiacusp
idata
Sorghastrumnutan
s
Koeleriapyramidat
a
Daisy fleabane
Erigeron strigosus
Pasque-flower
Anemone patens
Helianthus
pauciflorus
Hairy grama
Scribner’s panic
grass
Wilcox’s panic
grass
Boutelouahirsuta
Panicumoligosant
hes
Panicumwilcoxian
um
Echinacea pallida
Blue grama
Sand reed-grass
Needle-andthread grass
Prairie turnip
Potentillaarguta
Comandraumbellat
a
Pediomelumescule
ntum
Boutelouagracilis
Calamovilfalongif
olia
Prairie wild onion
Allium stellatum
Dotted blazing star
Liatrispunctata
Stiff sunflower
Narrow-leaved
purple coneflower
Tall cinquefoil
Bastard toad-flax
Plains muhly
Stipacomata
Shrubs and Semi-Shrubs
Leadplant
Prairie
rose
Smooth
sumac
Wolfberry
Amorphacanescens
Rosa arkansana
Rhusglabra
Symphoricarposoccid
entalis
25
Table 1 (continued)
Forbs, Ferns, and Fern Allies
Lithospermumcane
Hoary puccoon
scens
Aromatic aster
Virginia ground
cherry
Aster oblongifolius
Flodman's thistle
Cirsium flodmanii
Bird's foot coreopsis
Coreopsis palmata
Grooved yellow flax
Linumsulcatum
Ambrosia
psilostachya
Solidagocanadensi
s
Western ragweed
Canada goldenrod
Heart-leaved
alexanders
Wild bergamot
Physalisvirginiana
Ziziaaptera
Skyblue aster
Monardafistulosa
Campanula
rotundifolia
Calylophusserrulat
us
Solidagomissourie
nsis
Aster
oolentangiensis
Mock pennyroyal
Hedeomahispida
Prairie sagewort
Artemisia frigida
Hoary vervain
Tall wormwood
Verbena stricta
Euphorbia
corollata
Artemisia
ludoviciana
Asclepiasverticillat
a
Sisyrinchiumcamp
estre
Artemisia
dracunculus
Hairy golden aster
Chrysopsisvillosa
Prairie ragwort
Senecioplattensis
Kuhniaeupatorioid
es
Harebell
Toothed evening
primrose
Missouri goldenrod
Flowering spurge
White sage
Whorled milkweed
Field blue-eyed
grass
False boneset
False gromwell
Hairy puccoon
Onosmodiummolle
Asclepiasviridiflor
a
Lithospermumincis
um
Antennariaplantagi
nifolia
Lithospermumcaro
liniense
Silky prairie clover
Daleavillosa
Green milkweed
Narrow-leaved
puccoon
Plantain-leaved
pussytoes
Grasses and Sedges
Shrubs and Semi-Shrubs
26
Experimental Design
A randomized complete block design was used in this project (Figure 3).
Sixteen individual treatments were used per block in a 4 x 2 x 2 configuration. Four
blocks, or replicates, was established per each of two species: spotted knapweed and
common tansy. Each treatment consists of one of four seedbed preparations, one of
two cover crop types, one of two seed dispersal methods (Figure 4). A fourth factor,
consisting of a selective herbicide, was applied to these plots in May 2011.
Figure 3. A randomized complete block design (2x2x4). Each individual treatment will
have1of 4seedbed preparation types (Mowing, Mowing/Herbicide, Mowing/Herbicide/
Tilling, No seedbed preparation), 1 of 2 cover crop types (Canadian wild rye or No
cover crop), and 1 of 2 seed distribution methods for the native grass mixture (Hand
broadcasting versus Drill seeding). These individual treatment types were randomly
assigned their location in the block. 4 blocks total were assigned to each areas infested
with common tansy, spotted knapweed. M= mowing. H= herbicide. T=tilling. NP= no
preparation. C= cover crop. NC= no cover crop. HB= hand broadcasting. DS= drill
seeding. Half of each plot was sprayed with Milestone, a selective herbicide, in June
2011.
9-12 Canada Wild Rye
Cover Crop, CWR
M,C
M+H, C
M+H+T, C
NP, C
M, NC
M+H, NC
M+H+T, NC
NP, NC
M, C
M+H, C
M+H+T, C
NP, C
M, NC
M+H, NC
M+H+T, NC
NP, NC
9-16 Drill Seed Native Grass
mix, DS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1-8 Hand Broadcast Native
Grass mix, HB
1-4 Canada Wild Rye
Cover Crop, CWR
27
NO PREP
ONLY MOW
MOW AND
HERBICIDE
MOW, HERBICIDE,
AND TILL
Figure 4. Treatment assignments were determined by plots receiving a random number
between 1-16. Each number correlates with a specific seedbed preparation, cover crop
or control, and native grass mix seed dispersal method.
This resulted in a 4 x 2 x 2 x 2 factorial design with 32 individual treatments
per block, with four replicates of each block. Each block, before the fourth factor was
applied, consisted of sixteen treatment areas 10 meters by 20 meters with three meter
mowed buffer zones between treatment areas to prevent treatments having an effect on
one another. Each block is 107 meters by forty nine meters. Blocks were delineated in
late March 2010 at field locations within Camp Ripley that are of the appropriate size
28
and have an overall invasive percent cover of 25 percent or greater. GPS coordinates
of these locations were recorded. Mapping of plots was conducted pre-implementation
of treatments using ArcGIS 9.3©, produced by ESRI®. The plots were delineated
using rebar stakes to avoid losing boundary locations.
Procedures
Four seedbed preparations are being investigated: (1) Mowing (2) Mowing and
herbicide, (3) Mowing, herbicide application, and tilling, and (4) No seedbed
preparation. GPS locations of all blocks were recorded as shown in Table 2.
Table 2. UTM GPS Point Location of Blocks at Camp Ripley, MN
X
Y
Corner 1: 15N
388694
5110714
Corner 2: 15N
388750
5110713
Corner 3: 15N
388691
5110586
Corner 4: 15N
388665
5110703
Corner 1: 15N
387929
5111439
Corner 2: 15N
387883
5111299
Corner 3: 15N
387743
5111298
Corner 4: 15N
387729
5111413
Corner 1: 15N
388482
5111222
Corner 2: 15N
388400
5110917
Corner 3: 15N
388280
5110909
Corner 4: 15N
388284
5111205
Spotted Knapweed Block 1
Spotted Knapweed Blocks 2,3,4 (These blocks are in the
same field)
Common Tansy Blocks 1-4 (These blocks are in the same
field)
29
Seedbed preparations were conducted by Jamie Hanson and Kayla Malone.
Mowing of the treatment areas and buffer zones was done by Jamie Hanson and Kayla
Malone, using equipment at Camp Ripley. Herbicide was applied by Jamie Hanson
and Kayla Malone with a mounted gator sprayer with a one meter boom unit.
Glyphosate (RoundUp Pro®) was used as the herbicide spray treatment at 1.5%
solutionfor both invasive species. Tilling was done by Jamie Hanson and Kayla
Malone with equipment provided by the Department of Public Works at Camp Ripley.
Seedbed preparations were done from May 17 through June 11, 2010.
A cover crop and a control treatment is being investigated: (1) Canada wild rye
(Elymus canadensis), drilled at the rate of 11.2 kg per ha (10 pounds per acre), and
(2) No cover crop. The cover crop was implemented into the sites thirty days
following the seedbed preparations (early June 2010). Equipment used was a Tru-ax©
drill seeder. Canada wild rye was drilled into the soil at a depth of 6 cm. The cover
crop was implemented into the sites June 16-June 22, 2010.
Two seed dispersal methods of the native species mix are being investigated:
Hand broadcasting and no-till seed drilling. The drill seeder used for this project will
be a 2.44 meter wide (8 feet) three-point mount Tru-ax© drill seeder. Two seed
dispersal methods for the native grass seed mix were used: (1) Hand broadcasting,
(2) No-till drill seeding. Sites that were drill seeded were done at a depth of 1.3 cm.
The native grass species that will be used are as follows: Big bluestem (Andropogon
gerardii), little bluestem (Schizachyrium scoparium), Indian grass (Sorghastrum
nutans), side oats grama (Bouteloua curtipendula), switch grass (Panicum virgatum),
30
kalm’s brome (Bromus kalmii), June grass (Koeleria macrantha), and sand dropseed
(Sporobolus cryptandrus). This species mix was in the appropriate ratios as
recommended by Prairie Restorations Inc. Hand broadcastingwas done at the rate of
14.6 kg per ha (3 pounds per 10000 square feet). No-till drill seeding was done at the
rate of 11.2 kg per ha (10 pounds per acre), as recommended by the Prairie
Restorations Inc. catalog. The native grass mix was implemented into plots as a
dormant fall seeding from October 13-14, 2010.
Once all treatments were administered to the sites, buffer maintenance and data
collection was completed for the first growing season. Times of species emergence
were collected. Native species identification was difficult in the first growing season.
To mitigate this difficulty, the native seed mixture was also grown in a controlled
interior setting at Saint Cloud State University to assist in identification. Precipitation
was observed along with any extreme weather events. Data were collected in early
July, late July, and mid-August. Prairie grasses take time to establish and therefore it is
likely that the second and third growing season will have higher diversity. Grass
surveys were conducted yearly to gauge seeded grass species’ emergence.
Data were analyzed using a Univariate ANOVA and Repeated Measures
statistical analysis via a general linear model in the computer statistical software SPSS
17.0.
Data collected on site prior to experimental treatments included senescent
stand invasive plant percent cover measures, grass surveys, and forb surveys. Data
collected from April 12-14in 2010 showed that all blocks displayed an average-block
31
residual over-wintered dried stem percent cover measurements of over 25%. This
indicates that during peak growth of the invasive plants, the actual coverage is much
higher. Grass and forb surveys conducted throughout June and August indicate that
overall diversity in these highly infested experimental blocks is lower than in healthy
tallgrass prairie areas.
It was observed that spotted knapweed and common tansy germination rates
may have increased post disturbance in plots that were mowed, tilled, and drill seeded.
This result is not unexpected, as certain disturbances may invigorate the seed bank
present in the soil. A benefit of inducing germination is that emerging invasive plants
can be controlled post-germination and pre-flowering, therefore eliminating the seeds
and future plants that result from a dormant seed bank. To do this, while still being
able to analyze the effectiveness of combinations, it was decided that a selective
herbicide would have to be applied over all combinations except for areas that were
had no site preparation (those plots that were not mowed, herbicided, or tilled).
Milestone, as the selective herbicide of choice, was planned to be applied at the
appropriate maximum recommended label rate of 511.54 ml/hato half of every plot
using an ATV-mounted 3-point fan nozzle skid sprayer. The herbicide was applied on
May 25 and May 26 of 2011. Some variation occurred in spray application. Spotted
knapweed Block 1 was sprayed at the rate of 520.31 ml/ha, with total milestone
application of 105.28 ml in 75.71 liters H20. Spotted knapweed Block 2 was initially
oversprayed on the western side. The spray rate was corrected resulting in an overall
rate of 700.09 ml/ha, with total milestone application of 141.66 ml in 75.71 liters H20.
32
Spotted knapweed Block 3 was sprayed at the rate of 548.08 ml/ha, with total
milestone application of 110.61 ml in 79.49 liters H20. Spotted knapweed Block 4 was
sprayed at the rate of 548.08 ml/ha, with total milestone application of 110.61 ml in
79.49 liters H20. Common Tansy Block 1 was sprayed at the rate of 460.39 ml/ha,
with total milestone application of 93.15 ml in 79.49 liters H20. Common Tansy
Block 2 was sprayed at the rate of 482.31 ml/ha, with total milestone application of
97.59 mlin 83.28 liters H20. Common Tansy Block 3 was sprayed at the rate of
460.39 ml/ha, with total milestone application of 93.15 ml in 79.49 liters H20.
Common Tansy Block 4 was sprayed at the rate of 460.39 ml/ha, with total milestone
application of 93.16 ml in 79.49 liters H20.
2011 data collection involved multiple methods. Senescent stand percent cover
estimates were taken using two 1-m2 quadrats placed in the northwest and southeast
portions of each plot and an overall visual estimate of senescent target invasive
percent cover per plot. This was done April 18-25, 2011. Emergent stand percent
cover estimates were also taken using two 1-m2 quadrats placed in the northwest and
southeast portions of each plot and an overall visual estimate of senescent target
invasive percent cover per plot. This was done May 19-23, 2011. Post-Milestone
selective herbicide application, data was collected for invasive percent cover in the
same manner as previously stated during July 6-8, 2011. Species Richness data was
collected per plot between August 3-8, 2011. A 1-m2quadrat was randomly placed in
each half of plots, both on the half that received the selective herbicide, and also on
the untreated half. Total number of vascular plant species were counted, identified,
33
and recorded. During August 15-25, 2011 a cover class survey was conducted using a
daubenmire frame. The 20cm by 50cm frame was randomly placed in each half of
each plot. 6 cover class percent ranges were established: 1:1-5%, 2:6-25%, 3:26-50%,
4:51-75%, 5:76-95%, 6:96-100% and various classes were recognized including the
target invasive species of spotted knapweed, the target invasive species of common
tansy, non-native grasses such as smooth brome and quack grass, native grasses, nonnative forbs such as common mullein, native forbs, and bare ground. Tables 3 and 4
show the timeline of all procedures done to the study sites.
34
Table 3. Timeline of events in 2010
April
2nd, 7th: Marking
corners of blocks
May
3rd: No-prep
markers
finished in all
plots
June
1st-3rd :
Herbicide
applied to all
appropriate plots
July
6th:
Observation
of Rye
12th, 14th :
Percent cover
invasive data
collected
12th: Soil
sterilization,
grow room
started 161
grams seed mix
22nd: Data
collection
tilled area
that were
drill seeded
14th: Drill seed
and HB of natives
in Tansy plots:
Approx 10+ kg
PLS/ha
19th-26th: Postpounding: approx.
130 t-stakes and
cyber stake caps
17th-18th:
Mowing of
Spotted
Knapweed
Block 1, Tansy
Blocks 1,2,3,4
19th-20th:
Mowing of
Knapweed
Plots 2,3,4
4th, 7th: Mow
and Herbicide
Blue rebar
markers were
placed on
appropriate plots
9th-11th:
Tilling
26th: Tilled
areas that
were not drill
seeded were
observed
18th-22nd: Mow
and Herbicide
and Till Green
rebar markers
were placed on
appropriate plots.
16th: Drill
seeding Canada
Wild Rye in
Tansy 1-4,
Knapweed 2-3
except no-prep
plots,
22nd: Drill
seeding
Knapweed 4 and
1 and
appropriate noprep plots.
Approx. 6.73
to8.97 PLS
kg/ha
23rd-26th: Forb
surveys in all
yellow no prep
zones
30th: Grass
survey of all
no-prep plots
26th-30th: Noprep markers
(rebar) were
placed on
appropriate plots
24th-26th:
Mow-only pink
markers (rebar)
were placed on
appropriate
plots
28th:
Herbicide
applied to all
appropriate
plots
29th: Re-mow
of buffer zones
and pink mowonly plots.
August
27th: Remow of all
buffers
October
13th: Drill seed
and HB of natives
in Knapweed
plots: Approx
7.85 PLS kg/ha
35
Table 4. Timeline of events in 2011
April
8th-25th:
Senescent stand
data collection.
May
June
19th: Emergent
stand data
collection
Spotted
Knapweed.
27th: Mowed
SK 2 and 3
23rd: Emergent
stand data
collection
Common Tansy
29th: Mowed
SK 4
25th: Spray
Milestone on
Spotted
Knapweed
Blocks 2-4
26th: Spray
Milestone on
Spotted
Knapweed Block
1 and Tansy
Blocks 1-4
July
August
6th: Milestone %
cover invasive
data collection and
soil survey
Common Tansy 14 and plot
photographs
8th: Milestone %
cover invasive
data collection and
soil survey
Spotted Knapweed
1-4 and plot
photographs
11th: Sprayed
edges with wand
off gator. Sprayed
plot 10 and 14 in
Block 4 SK.
3, 5, 8th: Species
Richness data
collected
15-25th:
Daubenmeier
Cover Class Data
collected
Chapter 3
RESULTS
Initial Data Collection—2010
Spotted knapweed blocks and common tansy blocks were initially surveyed for
senescent visual estimation of percent cover of invasive plant percent cover in April
2010 using sixteen randomly obtained 1-m2 areas. Table 5 includes the mean percent
cover obtained for each block of the target invasive plant species in areas that were
infested with either spotted knapweed or common tansy.
All blocks contained over 25% senescent stand percent cover. Seedbed
preparations prevented the determination of emergent percent cover in 2010. The
emergent percent cover is projected to have been higher as can be observed by the
comparison of senescent versus emergent percent cover data obtained from control
plots in 2011. The mean initial percent cover in spotted knapweed blocks of spotted
knapweed was 43.7%. The mean initial percent cover in common tansy blocks of
common tansy was 30.9%.
Also in summer 2010, forb, tree, and grass surveys were conducted in control
plots in all blocks from June to August (Table 17, p. 49 and Table 19, p. 52). These
surveys involved the complete inventory of all identifiable grasses, tree species, and
forbs that existed within plots that received no seedbed preparations (plots numbered
36
37
4, 8, 12, and 16) in all blocks. Forb surveys were conducted June 21-26, 2010. Grass
surveys were conducted in the same manner from July 28-30, 2010. In spotted
knapweed and common tansy blocks, 42 forb and tree species were identified and
recorded. In spotted knapweed blocks, 17 grass species were identified and recorded.
In common tansy blocks, 13 grass species were identified and recorded.
Table 5. A random number generator was used to determine the number of steps
walked within the block to visually estimate senescent stand invasive species percent
cover in April 2010 of a meter sized area at that point with a total of 16 points per
block.
Spotted Knapweed Block
Mean Percent Cover (%)
1
39.7
2
45.9
3
49.1
4
40
Overall Mean
43.7
Common Tansy Block
Mean Percent Cover (%)
1
27.8
2
27.5
3
35.6
4
32.5
Overall Mean
30.9
Senescent Stand Data Collection—2011
Year 2011 mean overall estimates of percent cover of the four replicates of
each of the 16 plot treatment combinations for spotted knapweed and common tansy
blocks during senescence are shown in Tables 6 and 7. These mean percent covers
display the immediate impact of the previous summer’s treatments. As one could
38
predict, seedbed preparations can decrease the presence of senescent stands of the
target invasive species. However, this does not necessarily mean that this will result in
a subsequent decrease in emergence of invasive species post-germination. The overall
mean percent covers per blocks 1-4 of spotted knapweed and common tansy areas are
displayed in Table 8. Table 8 contains two mean percent covers per block. The first
mean percent cover is an overall visual estimate. Two 1-m2 random samples per plot
were also assessed for percent cover. The mean sample percent covers and mean
overall estimates were different for this particular data set, due to the sparse habit of
both invasive species and impact on other species’ presence during senescence. Larger
areas have a higher visual impact and resulting estimate. Table 8, when compared to
Table 5, reveals that post-treatment percent covers of senescent stands of the two
invasive species were reduced. Over all blocks, the mean percent cover was 10.921.2% in spotted knapweed areas versus the initial mean of 43.7%. Over all blocks,
the mean percent cover was 9.2-15.6% in common tansy areas versus the initial mean
of 30.9%.
39
Table 6. April 2011 senescent
stand mean percent cover of
spotted knapweed.
Table 7. April 2011 senescent stand
mean percent cover of common
tansy.
Treatment
Combination
(Four
replicates)
Mean Percent
Cover (%)
Treatment
Combination
(Four
replicates)
Mean Percent
Cover (%)
1
18.8
1
14.0
2
21.3
2
30.0
3
4.0
3
2.8
4
35.0
4
25.0
5
32.5
5
13.8
6
18.8
6
17.5
7
3.0
7
5.3
8
38.8
8
56.3
9
28.8
9
10.3
10
15.0
10
6.3
11
3.0
11
1.5
12
45.0
12
12.5
13
27.5
13
7.8
14
15.0
14
19.0
15
3.8
15
2.8
16
28.8
16
25.0
40
Table 8. A block mean of visual estimates of senescent stand invasive species percent
cover in April 2011 of each 10 by 20 meter plot. A block mean of two one meter
samples of senescent stand invasive species percent cover in April 2011 of each 10 by
20 meter plot.
Spotted
Knapweed
Block
Mean Visual Estimate of Plot
Percent Cover (%)
Mean Sample Percent Cover
(%)
1
2
3
4
16.9
24.3
24.4
19.2
8.7
12.8
12.3
9.8
Overall Mean
21.2
10.9
Common
Tansy Block
Mean Visual Estimate of Plot
Percent Cover (%)
Mean Sample Percent Cover
(%)
1
2
3
4
14.4
9.6
21.1
17.25
4.9
5.8
14.7
11.6
Overall Mean
15.6
9.2
Emergent Stand Data Collection—2011
Once vegetation began to emerge, it was observed that spotted knapweed and
common tansy were still very present in many plots that had shown a reduction in
percent cover when the senescent survey was done. Tables 9 and 10 contain the
emergent percent cover means for all treatment combinations applied to plots in
spotted knapweed areas and common tansy areas. Within Table 11, one can see the
mean percent cover measures per block for both species. The mean percent cover
measures in spotted knapweed areas per plot were at times higher post treatment, than
in 2010. This was also true, albeit to a lesser degree, in areas infested with common
41
tansy. Table 11, when compared to Table 5, reveals that post-treatment percent covers
of emergent stands of the two invasive species were not meaningfully reduced. Over
all blocks, the mean percent cover was 43.8-44.3% in spotted knapweed areas versus
the initial mean of 43.7%. Over all blocks, the mean percent cover was 20.8-25.6% in
common tansy areas versus the initial mean of 30.9%.
Table 9. May 2011 emergent
stand mean percent cover of
spotted knapweed.
Treatment
Combination
(Four
replicates)
Table 10. May 2011 emergent
stand mean percent cover of
common tansy.
Mean Percent
Cover (%)
Treatment
Combination
(Four
replicates)
Mean Percent
Cover (%)
1
33.8
1
30.0
2
43.8
2
46.3
3
47.5
3
12.5
4
26.3
4
17.5
5
40.0
5
35.0
6
51.3
6
28.8
7
68.8
7
16.3
8
32.5
8
46.3
9
47.5
9
23.8
10
42.5
10
32.5
11
51.3
11
15.0
12
47.5
12
10.0
13
47.5
13
17.5
14
35.0
14
41.3
15
66.3
15
15.0
16
27.5
16
22.5
42
Table 11. A block mean of visual estimates of emergent stand invasive species percent
cover in May 2011 of each 10 by 20 meter plot. A block mean of two one meter
samples of emergent stand invasive species percent cover in May 2011 of each 10 by
20 meter plot.
Spotted Knapweed
Block
Mean Visual Estimate of Plot Percent
Cover (%)
Mean Sample Percent Cover (%)
1
61.9
62.5
2
49.7
50.8
3
37.5
38.0
4
28.1
23.9
Overall Mean
44.3
43.8
Common Tansy
Block
Mean Visual Estimate of Plot Percent
Cover (%)
Mean Sample Percent Cover (%)
1
20.0
15.6
2
18.8
15.0
3
33.8
28.3
4
30.0
24.4
Overall Mean
25.6
20.8
Post-Milestone Application Data
Collection—2011
It was decided that the increase in percent cover that was observed in May
warranted an addition of another method of treatment. Since a reduction in percent
cover using the first three factors was not being observed it was decided that the
addition of a selective herbicide would be a valuable addition as a fourth factor in the
factorial design. Previous research and recommendation had shown that Milestone is a
reliable selective herbicide for the control of these two species (Beck, 2008) (M.
Halstvedt, personal communication, July 22, 2010).
43
To preserve the integrity of the factorial design, especially for the continued
monitoring of the effects of the first three factors in combination, this selective
herbicide was applied only on half of each 10 by 20 meter plot, thus producing a 4 by
2 by 2 by 2 design with 32 individual combinations. Five weeks after the application
of this selective herbicide to each half-plot, percent cover data was obtained per plot
for every block. Tables 12 and 13 show that during this data collection, there was far
less percent cover of either of the invasive species than that which can be seen in
Tables 9 and 10, which contain the emergent percent cover means for all treatment
combinations applied to plots in spotted knapweed areas and common tansy areas.
Spotted knapweed areas had lower percent cover measures for each treatment
combination that received the selective herbicide than the percent cover measures
taken on the common tansy plots with the same treatments. Table 14 also shows that
per block on all half-plots that received the selective herbicide, the percent cover was
reduced as compared to the emergent percent cover data obtained in May. Table 14,
when compared to Table 5, reveals that percent cover measures of post-milestone
application standswere reduced. Over all blocks, the mean percent cover was 1.31.9% in spotted knapweed areas versus the initial mean of 43.7%. Over all blocks, the
mean percent cover was 8.9-9.3% in common tansy areas versus the initial mean of
30.9%.
44
Table 12. July 2011 Postselective-herbicide treatment
mean percent cover of
spotted knapweed.
Table 13. July 2011 Postselective-herbicide treatment
mean percent cover of
common tansy.
Treatment
Combination
(Four
replicates)
Mean
Percent
Cover (%)
Treatment
Combination
(Four
replicates)
Mean
Percent
Cover (%)
1
0.0
1
7.8
2
11.0
2
17.5
3
0.3
3
4.8
4
0.3
4
3.5
5
2.0
5
3.5
6
0.5
6
17.8
7
2.5
7
11.3
8
0.3
8
6.8
9
1.0
9
5.3
10
3.3
10
14.5
11
1.5
11
9.3
12
1.0
12
2.0
13
1.0
13
4.0
14
2.0
14
21.5
15
4.5
15
9.0
16
0.3
16
4.0
45
Table 14. A block mean of visual estimates of post-selective-herbicide treatment
invasive species percent cover in July 2011 of each 10 by 20 meter plot. A block mean
of two one meter samples of post-selective-herbicide treatment invasive species
percent cover in 2011 of each 10 by 20 meter plot.
Spotted
Knapweed
Block
Mean Visual Estimate of Plot
Percent Cover (%)
Mean Sample Percent Cover
(%)
1
0.0
0.0
2
1.9
2.3
3
5.1
2.4
4
0.6
0.4
Overall Mean
1.9
1.3
Common Tansy
Block
Mean Visual Estimate of Plot
Percent Cover (%)
Mean Sample Percent Cover
(%)
1
6.4
5.1
2
2.8
3.9
3
15.4
15.9
4
10.9
12.2
Overall Mean
8.9
9.3
2011 Vegetation Surveys
A selective herbicide such as Milestone can also reduce other broadleaf species
within plots along with the targeted broadleaf invasive species. To measure the impact
that the herbicide had to species richness per plot, number of species were surveyed in
each half plot in August 2011. The selective herbicide did significantly reduce the
number of species within half-plots as compared to half-plots without the herbicide, as
shown in Tables 15 and 16.
46
During August 2011 the cover class survey that was conducted on half plots
with and without a Milestone application yielded the measures shown in Tables 21 and
22. The results of this cover class survey show that in spotted knapweed plot halves
with Milestone, spotted knapweed was reduced. However in these same plot halves,
undesirable non-native grass species proliferated. In common tansy plot halves with
Milestone, common tansy was reduced. In these same plot halves, undesirable nonnative grass species also thrived. It is also interesting to note that spotted knapweed
took over increasingly in common tansy areas, post all treatments.
Also in August 2011, forb, tree, and grass surveys were conducted in in all
blocks (Table 18 and 20). These surveys involved the complete inventory of all
identifiable grasses, tree species, and forbs that existed within all half-plotsin all
blocks. In spotted knapweed blocks 23 forb and tree species were identified and
recorded. In common tansy blocks, 29 forb and tree species were identified and
recorded. In spotted knapweed blocks, 11 grass species were identified and recorded.
In common tansy blocks, 11 grass species were identified and recorded. Number of
species was lower in all surveys conducted in 2011 versus those surveys in 2010. In
2010 84 forb and tree species, and 30 grass species were identified total in both
invasive species areas. In 2011, only 52 forb and tree species were identified, and only
22 grass species were identified total.
47
Table 15. 2011 Species Richness per half-plot (# spp.) with 1m squared quadrat
sampling frame randomly placed at least one meter from buffer zone (nm= half-plot
without selective herbicide, m= half-plot with selective herbicide applied).
Common Tansy Block 1 August 5
1 nm
8
1m
4
2 nm
8
2m
8
3 nm
9
3m
8
4 nm
9
4m
5
5 nm
9
5m
5
6 nm
9
6m
6
7 nm
4
7m
7
8 nm
4
8m
3
9 nm
10
9m
6
10 nm
8
10 m
4
11 nm
9
11 m
7
12 nm
6
12 m
6
13 nm
7
13 m
4
14 nm
10
14 m
4
15 nm
10
15 m
8
16 nm
5
16 m
4
Mean
7.8
5.6
Common Tansy Block 2 August3
1 nm
7
1m
2 nm
10
2m
3 nm
10
3m
4 nm
6
4m
5 nm
5
5m
6 nm
6
6m
7 nm
10
7m
8 nm
6
8m
9 nm
10
9m
10 nm
9
10 m
11 nm
7
11 m
12 nm
4
12 m
13 nm
10
13 m
14 nm
8
14 m
15 nm
9
15 m
16 nm
4
16 m
Mean
7.6
Common Tansy Block 3 August3
1 nm
5
1m
2 nm
10
2m
3 nm
10
3m
4 nm
9
4m
5 nm
5
5m
6 nm
7
6m
7 nm
12
7m
8 nm
8
8m
9 nm
4
9m
10 nm
10
10 m
11 nm
12
11 m
12 nm
10
12 m
13 nm
9
13 m
14 nm
7
14 m
15 nm
10
15 m
16 nm
8
16 m
Mean
8.5
Common Tansy Block 4 August 3
1 nm
5
1m
5
2 nm
10
2m
5
3 nm
10
3m
7
4 nm
12
4m
6
5 nm
8
5m
3
6 nm
9
6m
5
7 nm
10
7m
7
8 nm
6
8m
3
9 nm
7
9m
4
10 nm
8
10 m
5
11 nm
9
11 m
9
12 nm
8
12 m
5
13 nm
10
13 m
5
14 nm
5
14 m
9
15 nm
14
15 m
3
16 nm
7
16 m
5
Mean
8.6
5.4
4
6
9
6
5
6
3
6
4
9
6
5
4
6
8
6
5.8
4
5
6
4
4
5
4
3
4
5
3
6
6
6
5
4
4.6
48
Table 16. Species richness per half-plot (# spp.) with 1m squared quadrat sampling
frame randomly placed at least one meter from buffer zone (nm= half-plot without
selective herbicide, m= half-plot with selective herbicide applied).
Spotted Knapweed Block 1 August 8
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
5
5
5
4
4
5
4
7
4
7
3
5
7
4
7
6
5.125
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
5
6
3
2
3
3
2
4
3
6
3
4
3
4
5
2
3.625
Spotted Knapweed Block 3 August 8
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
7
7
10
10
11
14
4
9
11
5
14
9
11
7
11
11
9.4375
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
6
7
10
8
8
7
6
7
6
5
8
6
9
5
7
6
6.9375
Spotted Knapweed Block 2 August 5
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
11
9
10
6
8
7
7
9
9
6
6
6
9
7
6
9
7.8125
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
9
6
6
5
7
7
7
5
8
12
8
6
6
6
7
8
7.0625
Spotted Knapweed Block 4 August 8
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
13
10
17
12
9
11
16
8
6
15
19
11
16
13
18
15
13.0625
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
7
10
10
8
5
3
9
4
9
8
8
4
9
8
9
8
7.4375
49
Table 17. Forb and tree surveys in June and August 2010.
Forb and TreeSpecies Survey in Spotted
Knapweed Blocks in June and August
2010
Common Name
Scientific Name
Absinthium
Aslike Clover
Aspen Spp.
Bedstraw Spp.
Birch Spp.
Black Eyed Susan
Artemisia absinthium
Trifoliumhybridum
Populus
Galium
Betula
Rudbeckia hirta
Blackberry Spp.
Rubus
Bull Thistle
Common Chickweed
Common Mullein
Common Sorrel
Common Yarrow
Cirsiumvulgare
Stellaria media
Verbascum thapsus
Rumex acetosa
Achillea millefolium
Apocynum
cannabinum
Erigeron
Dogbane
Fleabane Spp.
Goat's Beard,
Western Salsify
Goldenrod Spp.
Forb and Tree Species Survey in
Common Tansy Blocks in June and
August 2010
Common Name
Absinthium
Aslike Clover
Birch Spp.
Black Eyed Susan
Bladder Campion
Butter & Eggs
Common
Cinquefoil
Common Mullein
Common Sorrel
Common Yarrow
Cow Vetch
Deptford Pink
Scientific Name
Artemisia absinthium
Trifoliumhybridum
Betula
Rudbeckia hirta
Silene nivea
Linariavulgaris
Potentilla simplex
Evening Lychnis
Verbascum thapsus
Rumex acetosa
Achillea millefolium
Vicia cracca
Dianthus armeria
Apocynum
cannabinum
Lychnis alba
Tragopogon dubius
Fleabane Spp.
Erigeron
Solidago
Solidago
Chrysopsisgraminifol
i
Arabishirsuta
Berteroaincana
Trifolium aureum
Conyzacanadensis
Dogbane
Hoary Alyssum
Berteroaincana
Horseweed
Indian Paintbrush
Milkweed Spp.
Mustard Spp.
Conyzacanadensis
Castillejacoccinea
Asclepias
Brassica
Goldenrod Spp.
Grass leaved golden
aster
Hairy Rock Cress
Hoary Alyssum
Hop Clover
Horseweed
Night-flowering
Lychnis
Silene noctiflora
Milkweed Spp.
Asclepias
Quercus
Toxicodendronradica
ns
Potentilla
Mustard Spp.
Night-flowering
Catchfly
Nightshade Spp.
Brassica
Oak Spp.
Poison Ivy
Prairie Cinquefoil
Silenoctiflora
Solanum
50
pensylvanica
Table 17 (continued)
Forb and TreeSpecies Survey in Spotted
Knapweed Blocks in June and August
2010
Common Name
Scientific Name
Forb and Tree Species Survey in
Common Tansy Blocks in June and
August 2010
Common Name
Scientific Name
Symphyotrichumlanc
eolatum
Plantago
Toxicodendronradica
ns
Potentilla
pensylvanica
Rosa arkansana
Artemisia
ludoviciana
Prairie Rose
Rosa arkansana
Panicled Aster
Purple Clover
Trifolium purpureum
Plantain Spp.
Purple Vetch
Vicia americana
Poison Ivy
Quaking Aspen
Populus tremuloides
Prairie Cinquefoil
Rabbit's foot Clover
Trifolium arvense
Prairie Rose
Red Clover
Trifolium pratense
Prairie Sage
Salix
Purple Vetch
Vicia americana
Potentillaargentea
Trifolium pratense
Tall Cinquifoil
Rhusglabra
Hypericumperforatu
m
Potentillaarguta
Red Clover
Rough Fruited
Cinquefoil
Silvery Cinquefoil
Slender Leaved
Aster
Smooth rock cress
Vetchling Spp.
Lathyrus
Spotted Knapweed
Sandbar Willow
Spp.
Silvery Cinquefoil
Slender Leaved
Aster
Smooth Sumac
St. John's Wort
Virginia Creeper
Wild Strawberry
Willow Spp.
Yellow Sweet
Clover
Aster tenuifolius
Parthenocissusquinq
uefolia
Fragariavirginiana
Salix
Melilotusindicus
Vetchling Spp.
Potentilla recta
Potentillaargentea
Aster tenuifolius
Arabiscanadensis
Centaurea stoebe ssp.
micranthos
Lathyrus
White Campion
Silene latifolia
White Sweet Clover Melilotus alba
Wild Strawberry
Fragariavirginiana
51
Table 18. Forb and tree surveys in August 2011.
Forb and Tree Species Survey in Spotted
Knapweed Blocks in August 2011
Common Name
Blackberry
Black Eyed Susan
Campion Spp.
Cinquefoil Spp.
Clover Spp.
Common Yarrow
Field Bindweed
Fleabane Spp.
Goldenrod Spp.
Hoary Alyssum
Common Mullein
Plantain Spp.
Poison Ivy
Rabbit's Foot
Clover
Rough Cinquefoil
Smartweed Spp.
Smooth Sumac
Vetchling Spp.
Virginia Creeper
White Sweet
Clover
Wild Strawberry
Willow Spp.
Yellow Wood
Sorrel
Scientific Name
Rubus
Rudbeckia hirta
Silene
Potentilla
Trifolium
Achillea millefolium
Convolvulus
Erigeron
Solidago
Berteroaincana
Verbascum thapsus
Plantago
Toxicodendronradicans
Forb and Tree Species Survey in Common Tansy
Blocks in August 2011
Common Name
Absinthium
Black Eyed Susan
Bull Thistle
Butter & Eggs
Campion Spp.
Canada Thistle
Cinquifoil Spp.
Bedstraw Spp.
Clover Spp.
Common Mullein
Common Yarrow
Dogbane
Fleabane Spp.
Goat's Beard,
Western Salsify
Goldenrod Spp.
Hawkweed
Hoary Alyssum
Milkweed Spp.
Scientific Name
Artemisia absinthium
Rudbeckia hirta
Cirsiumvulgare
Linariavulgaris
Silene
Cirsium arvense
Potentilla
Galium
Trifolium
Verbascum thapsus
Achillea millefolium
Apocynum cannabinum
Erigeron
Poison Ivy
Toxicodendronradicans
Melilotus alba
Prairie Dock
Silphiumterebinthinaceum
Fragariavirginiana
Salix
Prairie Rose
Primrose
Rosa arkansana
Primula vulgaris
Oxalis stricta
Smartweed Spp.
Polygonum
Trifolium arvense
Potentillanorvegica
Polygonum
Rhusglabra
Lathyrus
Parthenocissusquinquef
olia
Spotted Knapweed
St. John's Wort
Vetchling Spp.
Wild Strawberry
Willow spp.
Yellow Wood Sorrel
Tragopogon dubius
Solidago
Hieraciumlachenalii
Berteroaincana
Asclepias
Centaurea stoebe ssp.
micranthos
Hypericumperforatum
Lathyrus
Fragariavirginiana
Salix
Oxalis stricta
52
Table 19. Grass surveys in August 2010.
Grass Species Survey in Spotted
Knapweed Blocks in August 2010
Common Name
Scientific Name
Grass Species Survey in Common
Tansy Blocks in August 2010
Common Name
Scientific Name
Awlfruit Sedge
CarexStipata
Big Bluestem
Grass
Big Bluestem
Andropogngerardii
Green Foxtail
Setariaviridis
Horsetail
June Grass
Kentucky Blue
Grass
Equisetum arvense
Koeleriamacrantha
Little Bluestem
Love Grass Spp.
Panic Grass Spp.
Purple Love Grass
Quack Grass
Redtop Grass
Side-oats Grama
Smooth
Bromegrass
Switch Grass
Tall Grama Grass
Timothy Grass
Poapratensis
Schizachyrium
scoparium
Eragrostis
Panicum
Eragrostisspectabilis
Elymus repens
Agrostisgigantea
Bouteloua
curtipendula
Bromusinermis
Panicumvirgatum
Bouteloua
curtipendula
Phleumpratense
Blue Joint Grass
Deer Tongue
Grass
Green Foxtail
Grass
Horsetail
Andropogngerardii
Calamagrostiscanade
nsis
Panicumclandestinum
Setariaviridis
Equisetum arvense
June Grass
Kentucky Blue
Grass
Love Grass Spp.
Panic Grass Spp.
Quack Grass
Redtop Grass
Smooth
Bromegrass
Koeleriamacrantha
Timothy Grass
Phleumpratense
Poapratensis
Eragrostis
Panicum
Elymus repens
Agrostisgigantea
Bromusinermis
53
Table 20. Grass surveys in August 2011.
Grass Species Survey in Spotted
Knapweed Blocks in August 2011
Common Name
Scientific Name
Bottlebrush Sedge
Carex comosa
Canada Wild Rye
Elymus Canadensis
Panicumclandestinu
Deer Tongue Grass m
Indian Grass
Sorghastrum nutans
June Grass
Koeleriamacrantha
Kentucky Blue
Grass
Poapratensis
Love Grass Spp.
Eragrostis
Panic Grass Spp.
Panicum
Sedge Spp.
Carex
Smooth Brome
Grass
Bromusinermis
Timothy Grass
Phleumpratense
Grass Species Survey in Common Tansy
Blocks in August 2011
Common Name
Scientific Name
Bottlebrush Sedge
Carex comosa
Canada Wild Rye
Elymus Canadensis
Panicumclandestinu
Deer Tongue Grass m
Horsetail
Equisetum arvense
June Grass
Koeleriamacrantha
Kentucky Blue
Grass
Poapratensis
Panic Grass Spp.
Panicum
Quack Grass
Elymus repens
Redtop Grass
Agrostisgigantea
Smooth Brome
Grass
Bromusinermis
Timothy Grass
Phleumpratense
54
Table 21. Cover class mean values for every treatment of the four blocks in spotted
knapweed areas was determined by randomly placing a 0.2 by 0.5 m Daubenmire
frames in each half-plot. Values correspond to a scale of percentage ranges: 1-5%=1,
6-25%=2, 26-50%=3, 51-75%=4, 76-95%=5, 96-100%=6.
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
Mean
Spotted
Knapweed
3.0
4.5
2.8
3.0
3.0
3.0
4.3
3.5
3.3
3.3
3.5
3.8
4.5
2.8
3.0
2.5
3.3
Common
Tansy
Nonnative
forbs
Native
forbs
1.3
1.0
1.8
1.0
1.7
1.3
1.0
1.5
1.3
1.5
1.7
1.5
2.3
1.3
1.5
1.5
1.0
1.0
1.0
1.0
0
1.0
1.0
1.7
2.0
1.0
3.0
1.7
1.7
1.0
1.4
Native
grass spp.
1.8
1.0
1.5
1.0
2.3
1.0
1.0
1.3
1.5
1.0
1.5
1.5
1.3
2.0
2.0
2.0
1.5
2.0
2.0
3.5
2.0
2.5
2.0
2.5
2.3
2.0
3.5
3.0
2.5
2.5
2.3
2.5
2.3
2.5
Non-native
grass spp.
2.0
1.0
2.0
3.0
1.3
1.7
1.5
2.0
1.7
2.0
1.5
2.0
1.3
1.7
1.3
2.3
1.8
5.7
4.5
2.7
5.3
4.0
5.0
2.7
4.3
4.7
4.7
3.3
4.3
3.3
4.0
3.5
5.0
4.1
Bare
Ground
2.0
2.3
2.0
3.5
1.0
2.5
2.3
1.5
2.0
3.3
2.3
1.3
1.7
1.8
3.3
2.5
2.2
2.5
2.0
2.0
3.0
2.0
2.0
3.0
3.0
2.7
2.0
2.0
2.3
2.7
2.0
2.8
1.3
2.3
55
Table 22. Cover class mean values for every treatment of the four block in common
tansy areas was determined by randomly placing a 0.2 by 0.5 m Daubenmire frames in
each half-plot. Values correspond to a scale of percentage ranges: 1-5%=1, 6-25%=2,
26-50%=3, 51-75%=4, 76-95%=5, 96-100%=6.
Spotted
Knapweed
1 nm
2 nm
3 nm
4 nm
5 nm
6 nm
7 nm
8 nm
9 nm
10 nm
11 nm
12 nm
13 nm
14 nm
15 nm
16 nm
Mean
1m
2m
3m
4m
5m
6m
7m
8m
9m
10 m
11 m
12 m
13 m
14 m
15 m
16 m
Mean
3.0
4.5
4.0
4.5
1.0
4.0
1.5
4.0
4.0
3.0
3.0
3.3
Common
Tansy
4.3
2.3
3.0
3.3
3.0
3.7
3.0
3.5
3.0
5.0
2.7
3.5
3.0
3.7
1.5
2.3
3.2
3.5
1.5
Nonnative
forbs
1.0
2.0
2.0
1.0
2.0
2.0
2.0
2.0
2.0
1.7
1.7
3.3
2.0
1.9
2.0
2.0
Native
forbs
2.0
2.3
2.3
1.7
1.7
2.0
2.7
2.0
2.0
1.5
3.0
2.0
1.3
2.0
2.0
2.5
2.1
2.0
2.0
1.7
1.5
3.0
2.0
3.0
1.0
3.0
3.0
0
2.0
2.0
2.0
2.3
1.5
2.0
1.7
2.5
2.7
2.0
1.3
1.0
1.3
1.5
1.0
1.3
1.3
1.7
1.0
1.5
1.5
1.7
1.5
Native
grass
spp.
1.0
1.0
2.0
1.0
1.0
1.0
1.5
1.0
1.0
1.3
1.0
1.0
1.0
1.1
1.0
3.0
3.8
1.0
1.0
2.3
2.0
2.0
1.7
2.0
3.5
2.0
1.3
1.7
3.5
2.0
2.1
Non-native
grass spp.
2.7
2.0
1.0
2.8
2.3
2.5
1.0
2.7
3.5
1.0
2.5
2.8
2.0
1.0
3.8
2.2
4.7
2.8
1.7
5.5
5.0
3.5
3.0
5.7
5.0
2.3
1.7
4.8
5.0
3.3
2.0
4.8
3.8
Bare
Ground
1.0
1.0
1.0
1.0
1.0
1.0
1.7
2.0
1.3
1.0
1.2
4.0
1.0
2.0
1.5
2.0
2.3
1.0
1.0
1.5
1.0
2.0
1.0
1.7
56
Statistical Analyses
Year 2011 mean overall estimates of percent cover of the four replicates of
each of the 16 plot treatment combinations of invasive species during emergence premilestone are also compared using SPSS 17.0. A Univariate ANOVA was conducted
to determine which, if any, of the treatments affected invasive plant mean percent
cover to a statistically significant degree. Table 25 shows that in the case of areas
infested with spotted knapweed, the only statistically significant variable that affected
the dependent variable, mean percent cover, was the application of a selective
herbicide, Milestone, F (1,124) = 56.258, p < .05. All other treatments had no
statistically significant, or at this time, biologically significant effect on invasive plant
percent cover of plots. Table 29 shows that in the case of areas infested with common
tansy, the only statistically significant variable that affected the dependent variable,
mean percent cover, was the application of a selective herbicide, Milestone, F (1,124)
= 11.465, p < .05. All other treatments had no statistically significant effect on
invasive plant percent cover of plots.
A repeated measures ANOVA was also used in this experiment because all
data collected are measured over different times. The measurement of the dependent
variable, percent cover, is repeated. This analysis detects if time affected mean percent
cover of vegetation. When time is incorporated as an independent variable, what is
really being determined is if the four data sets collected at four different times, have
statistically significant difference between mean percent cover. The four times of data
collection reflect 2010 initial mean percent cover, 2011 senescent stand mean percent
57
cover, 2011 emergent stand percent cover, and 2011 post-milestone stand percent
cover. Tables 27 and 31 show that in both the case of spotted knapweed and common
tansy, time was a significant within-subjects effect. Mean percent cover was
significantly different between the four times of data collection (F (3,183) = 64.597,
p < .05, F (3,189) = 18.56, p < .05).
Using the repeated measures ANOVA, Individual spotted knapweed blocks
were not significantly different in measures of percent cover from each other. This
suggests that placement and treatment application were successfully done to the blocks
so that they act as effective replicates. Individual common tansy blocks were
significantly different in measures of percent cover over time from each other
(F (3, 60) = 2.957, p < .05). This suggests that placement and/or treatments increased
variability in blocks. Environmental variability and consistent execution of large-scale
treatments can have an effect on the establishment of replicates in large-scale studies
of vegetation.
The milestone treatment did reduce the overall invasive plant presence, but to
evaluate the effect of the selective herbicide on other species, a t-test of the species
richness of 4 replicates of each of the 16 plot halves with and without milestone
application were conducted for both spotted knapweed and common tansy areas.
Tables 23 and 24 shows that differences between mean number of species in plot
halves with milestone and without the selective herbicide were statistically significant
for both common tansy and spotted knapweed areas (t (126) = 7.98, p < .05, t (126) =
58
4.65, p < .05).There was less overall species richness in plot halves that had a selective
herbicide applied.
Table 23. Common tansy independent samples t-test for species richness in plot halves
with and without a selective herbicide application. Means differed significantly. T
(126) = 7.98, p < .05.
Levene's Test for
Equality of
Variances
t-test for Equality of Means
95% Confidence
Interval of the
Sig.
(2F
Equal variances
7.210
Sig.
t
.008 7.983
df
Mean
Std. Error
Difference
tailed) Difference Difference Lower
Upper
126
.000
2.781
.348
2.092
3.471
7.983 114.304
.000
2.781
.348
2.092
3.471
assumed
Equal variances
not assumed
59
Table 24. Spotted knapweed independent samples t-test for species richness in halfplots with and without a selective herbicide application. t (126) = 4.65, p < .05.
Levene's Test for
Equality of
Variances
t-test for Equality of Means
95% Confidence
Interval of the
Sig.
(2F
Equal variances
Sig.
14.330
t
df
.000 4.654
Mean
Std. Error
Difference
tailed) Difference Difference Lower
Upper
126
.000
2.594
.557
1.491
3.697
4.654 102.266
.000
2.594
.557
1.488
3.699
assumed
Equal variances
not assumed
Table 25. Univariate ANOVA for spotted knapweed areas with the Between-Subjects
factors of seedbed preparation (SP), cover crop (CC), seeding method (SM), selective
herbicide application (MS), and block. The only statistically significant factor was the
application of the selective herbicide, Milestone. F (1,124) = 56.258, p < .05.
Tests of Between-Subjects Effects
Dependent Variable:Percent Cover
Type III Sum
Source
of Squares
df
Mean Square
F
Sig.
Corrected Model
81961.495a
129
635.360
.879
.765
Intercept
65240.041
1
65240.041
90.272
.000
SP
80.908
3
26.969
.037
.990
CC
14.560
1
14.560
.020
.887
SM
1785.208
2
892.604
1.235
.294
MS
40658.183
1
40658.183
56.258
.000
60
Table 25 (continued)
Type III Sum
Source
Block
of Squares
df
Mean Square
F
Sig.
1475.848
3
491.949
.681
.565
SP * CC
625.412
3
208.471
.288
.834
SP *SM
719.483
3
239.828
.332
.802
SP * MS
252.058
3
84.019
.116
.950
SP * Block
612.407
9
68.045
.094
1.000
CC * SM
152.427
1
152.427
.211
.647
CC * MS
42.052
1
42.052
.058
.810
CC * Block
867.235
3
289.078
.400
.753
SM * MS
133.477
1
133.477
.185
.668
SM * Block
560.505
6
93.418
.129
.992
MS * Block
1352.674
3
450.891
.624
.601
SP * CC * SM
333.133
3
111.044
.154
.927
SP * CC * MS
249.193
3
83.064
.115
.951
1120.638
9
124.515
.172
.996
108.494
3
36.165
.050
.985
SP * SM * Block
1661.722
9
184.636
.255
.985
SP * MS * Block
1099.417
9
122.157
.169
.997
CC * SM * MS
451.560
1
451.560
.625
.431
CC * SM * Block
111.853
3
37.284
.052
.984
CC * MS * Block
629.949
3
209.983
.291
.832
SM * MS * Block
580.275
3
193.425
.268
.849
SP * CC * SM * MS
166.309
3
55.436
.077
.972
SP * CC * SM * Block
876.240
9
97.360
.135
.999
SP * CC * MS * Block
982.288
9
109.143
.151
.998
SP * SM * MS * Block
151.440
8
18.930
.026
1.000
CC * SM * MS * Block
47.938
3
15.979
.022
.996
SP * CC * Block
SP * SM * MS
61
Table 25 (continued)
Source
Type III Sum
df Mean Square
F
Sig.
.050
1.000
of Squares
SP * CC * SM* MS
291.958
8
36.495
Error
89615.313
124
722.704
Total
370321.000
254
Corrected Total
171576.807
253
*Block
a. R Squared = .478 (Adjusted R Squared = -.066)
Table 26. Univariate ANOVA for spotted knapweed. Means reported and descriptive
statistics.
Second Year Milestone
Dependent Variable:Percent Cover
95% Confidence Interval
SecondYear
Milestone
Mean
No MS
36.380
1.548
33.331
39.429
1.935
2.724
-3.430
7.301
MS
Std. Error Lower Bound
Upper Bound
62
Table 27. Repeated Measures ANOVA for spotted knapweed areas with the WithinSubjects Effects of time on mean percent cover. Time was a statistically significant
factor. F (3,183) = 64.597, p < .05.
Tests of Within-Subjects Effects
Type III Sum of
Source
Time
Error(time)
Squares
df
Mean Square
F
Sig.
Sphericity Assumed
78722.077
3
26240.692
64.597
.000
Greenhouse-Geisser
78722.077
2.182
36073.563
64.597
.000
Huynh-Feldt
78722.077
2.266
34735.477
64.597
.000
Lower-bound
78722.077
1.000
78722.077
64.597
.000
Sphericity Assumed
74338.173
183
406.220
Greenhouse-Geisser
74338.173
133.118
558.437
Huynh-Feldt
74338.173
138.246
537.723
Lower-bound
74338.173
61.000
1218.659
Table 28. Repeated Measures ANOVA for spotted knapweed. Means reported and
descriptive statistics.
Time
95% Confidence Interval
Time
Mean
Std. Error
Lower Bound
Upper Bound
1
43.710
3.495
36.721
50.698
2
21.613
2.087
17.440
25.786
3
45.403
2.640
40.124
50.683
4
1.935
.687
.562
3.309
63
Table 29. Univariate ANOVA for common tansy areas with the Between-Subjects
factors of seedbed preparation (SP), cover crop (CC), seeding method (SM), selective
herbicide application (MS), and block.The only statistically significant factor was the
application of the selective herbicide, Milestone. F (1,124) =11.465, p<.05. Seedbed
preparation is significant due to replicates being significantly different in mean overall
percent cover.
Tests of Between-Subjects Effects
Dependent Variable:Percent Cover
Type III Sum of
Source
Squares
df
Mean Square
F
Sig.
Corrected Model
61349.797a
131
468.319
.916
.689
Intercept
40651.792
1
40651.792
79.544
.000
SP
4612.917
3
1537.639
3.009
.033
CC
472.594
1
472.594
.925
.338
SM
1392.828
2
696.414
1.363
.260
MS
5859.375
1
5859.375
11.465
.001
Block
3935.564
3
1311.855
2.567
.058
SP * CC
1157.615
3
385.872
.755
.521
SP * SM
649.375
3
216.458
.424
.736
SP * MS
2786.375
3
928.792
1.817
.147
SP * Block
3363.937
9
373.771
.731
.679
CC * SM
.094
1
.094
.000
.989
CC * MS
119.260
1
119.260
.233
.630
81.469
3
27.156
.053
.984
682.667
1
682.667
1.336
.250
SM * Block
1698.505
6
283.084
.554
.766
MS * Block
21.271
3
7.090
.014
.998
SP * CC * SM
1004.865
3
334.955
.655
.581
SP * CC * MS
906.281
3
302.094
.591
.622
1334.073
9
148.230
.290
.976
CC * Block
SM * MS
SP * CC * Block
64
Table 29 (continued)
Type III Sum of
Source
df
Mean Square
F
Sig.
311.750
3
103.917
.203
.894
SP * SM * Block
1738.271
9
193.141
.378
.944
SP * MS * Block
566.063
9
62.896
.123
.999
1.260
1
1.260
.002
.960
CC * SM * Block
565.010
3
188.337
.369
.776
CC * MS * Block
588.385
3
196.128
.384
.765
SM * MS * Block
369.021
3
123.007
.241
.868
SP * CC * SM * MS
490.865
3
163.622
.320
.811
SP * CC * SM * Block
3415.115
9
379.457
.742
.669
SP * CC * MS * Block
1283.156
9
142.573
.279
.979
SP * SM * MS * Block
330.313
9
36.701
.072
1.000
CC * SM * MS * Block
419.260
3
139.753
.273
.844
1343.031
9
149.226
.292
.976
Error
63371.188
124
511.058
Total
229616.000
256
Corrected Total
124720.984
255
SP * SM * MS
CC * SM * MS
SP * CC * SM * MS*
Squares
Block
a. R Squared = .492 (Adjusted R Squared = -.045)
65
Table 30. Univariate ANOVA for common tansy. Means reported and descriptive
statistics.
Second Year Milestone
Dependent Variable:Percent Cover
95% Confidence Interval
Second Year
Milestone
Mean
No MS
24.026
1.527
21.019
27.033
8.891
2.645
3.682
14.099
MS
Std. Error Lower Bound
Upper Bound
Table 31. Repeated Measures ANOVA for common tansy areas with the WithinSubjects Effects of time on mean percent cover. F (3,189) = 18.56, p < .05.
Tests of Within-Subjects Effects
Type III Sum of
Source
Time
Error(time)
Squares
df
Mean Square
F
Sig.
Sphericity Assumed
18698.578
3
6232.859
18.565
.000
Greenhouse-Geisser
18698.578
1.760
10626.497
18.565
.000
Huynh-Feldt
18698.578
1.806
10352.142
18.565
.000
Lower-bound
18698.578
1.000
18698.578
18.565
.000
Sphericity Assumed
63453.422
189
335.732
Greenhouse-Geisser
63453.422
110.856
572.395
Huynh-Feldt
63453.422
113.794
557.617
Lower-bound
63453.422
63.000
1007.197
66
Table 32. Repeated Measures ANOVA for common tansy. Means reported and
descriptive statistics.
Time
95% Confidence Interval
Time
Mean
Std. Error
Lower Bound
Upper Bound
1
30.859
3.616
23.633
38.086
2
15.594
2.330
10.937
20.251
3
25.625
2.464
20.702
30.548
4
8.891
1.310
6.272
11.509
Boxplot Figures
SPSS Boxplots consist of box length, which reflects sample variability. The
median value of the sample is displayed as a horizontal line within the box. Box plots
which reflect a normally distributed sample will have tails as long as the box. If one
tail is longer, than the means are skewed in a certain direction. The bottom of the box
represents the first quartile of the sample; the top of the box shows the third quartile.
Outliers are also shown, asterisks being more extreme outliers. The labels next to
outliers are the data labels from the original data sheet.
Using SPSS 17.0, Boxplot graphs were produced to visually depict
relationships between experimental blocks and invasive mean percent cover, data sets
and invasive mean percent cover, and the effect of Milestone on plot halves’ invasive
mean percent cover. Figure 5 (spotted knapweed) and Figure 8 (common tansy)
compare boxplots of individual blocks’ ranges of invasive mean percent cover.
67
Figure 6 (spotted knapweed) and Figure 9 (common tansy) compare boxplots of
ranges of invasive mean percent cover between data sets (time). Figure 7 (spotted
knapweed) and Figure 10 (common tansy) compare boxplots of ranges of invasive
mean percent cover between plot halves that were treated with Milestone, and plot
Mean Percent Cover (%)
halves that had no selective herbicide applied.
Spotted Knapweed Data Sets
Figure 5. Spotted knapweed blocks’ mean percent cover measures for all data sets.
There was no statistical significance found for differences between replicates, p < .05.
Mean Percent Cover (%)
68
Spotted Knapweed Data Sets
Figure 6. Spotted knapweed mean percent cover measures per data set. RS10 =
random sample data of initial invasive percent cover obtained before treatments were
applied in 2010. S11 = Senescent stand invasive percent cover recorded in April
2011. E11 = Emergent invasive percent cover obtained in May 2011. PM11 = Postmilestone selective herbicide application data recorded from half-plots that received
the selective herbicide.
Mean Percent Cover (%)
69
Invasive Presence Without and With a Selective Herbicide Application
Figure 7. Spotted knapweed mean percent cover measures for plot halves within
blocks that received no selective herbicide versus those half-plots that received a
selective herbicide application (nms = no milestone applied, ms = milestone applied).
Mean Percent Cover (%)
70
Common Tansy Block
Figure 8. Common tansy mean percent cover measures per block. There was a
statistically significant difference between replicates for the measures obtained over all
data sets, p < .05.
Mean Percent Cover (%)
71
Common Tansy Data Sets
Figure 9. Common tansy mean percent cover measures per data set. RS10 = random
sample data of initial invasive percent cover obtained before treatments were applied in
2010. S11 = Senescent stand invasive percent cover recorded in April 2011. E11 =
Emergent invasive percent cover obtained in May 2011. PM11 = Post-milestone
selective herbicide application data recorded from half-plots that received the selective
herbicide.
Mean Percent Cover (%)
72
Invasive Presence Without and With a Selective Herbicide Application
Figure 10. Common tansy mean percent cover measures for plot halves within blocks
that received no selective herbicide versus those half-plots that received a selective
herbicide application (mns = no milestone applied, ms = milestone applied).
Chapter 4
DISCUSSION
The objective of this thesis project was to use a successional management
method of restoring perennial invasive-species-dominated areas into a native plant
community as has been promoted by Pickett et al. (1987) and Sheley et al. (1996a).
This method incorporated various treatments including seedbed preparations, cover
crop implementation, and seed dispersal methods. I hypothesized that by introducing a
competitive cover crop immediately upon intentional disturbance of these invaded
areas, followed by the seeding of native grasses, a decrease in target invasive species’
percent cover measures would occur. The null hypothesis states that these treatments
would have no effect on invasive plant percent cover measures. I fail to reject the null
hypothesis, at this point in time, upon doing the statistical analysis. I also hypothesized
that drill seeding will be the most effective means of establishing native grasses in the
seedbed. This hypothesis is difficult to measure and statistically support because of the
phenology and short duration of this study. However, based on observation alone, I
would be willing to conclude that drill seeding is generally more effective as seeded
native grasses were more visually evident in plots that had been drill-seeded versus the
method of hand-broadcasting. I also hypothesized that the most successful decrease in
invasive plant percent cover would occur on sites that are mowed and then sprayed
73
74
with a non-selective herbicide. The null hypothesis in this case would be that invasive
plant percent cover would not be affected by this treatment combination. We fail to
reject the null hypothesis, upon investigating the statistics. Though we failed to reject
the null hypotheses at this time, it is suggested that future monitoring and data
collection be conducted on the experimental sites. This is especially advised due to the
nature of succession as a pathway that changes as time increases. Also, the level of
degradation in these sites is to such a degree that recovery time will be years long. The
integration of native seeds in sites that have been negatively impacted by invasion has
been recommended by previous literature. In many cases, native seeds reduced
invasive plant percent cover over time (Lym &Tober, 1997, Bottoms & Whitson,
1998, Ferrell, Whitson, Koch, & Gade, 1998; Masters & Nissen, 1998). The
experimental sites inn this project may show a similar reduction in future data sets.
The cover crop of Canada wild rye implemented into sites emerged
successfully in plots 3 and 11, both of which were tilled. Other plots that received the
cover crop had less Canada wild rye present. The low amount of precipitation in 2010
may have reduced cover crop establishment in untilled plots.
It is hoped that continued data collected in the summer of 2012 and perhaps
beyond, will ultimately result in the determination of the best integrated management
practices for reducing spotted knapweed and common tansy in tall grass prairie
systems. Mowing, herbicide application, tilling, cover crops, and the introduction of
native seed are management strategies that in the proper combination have contributed
to the effective restoration of degraded sites (Masters & Sheley, 2001). This
75
information is highly valuable for land managers in Minnesota. Certain treatment
combinations can lead to dramatic decreases in destructive invasive plant species
abundance. It is strongly recommended that continued data collection occur on sites
for the at least one more growing season to see if the multitude of treatments and
seeding efforts increases native species presence and decrease s invasive species
presence .
On a separate note, mammals such as skunks and ground squirrels were seen to
disturb soil in plots by burrowing and digging. It would also be of interest to
determine if these activities facilitate the dispersal of spotted knapweed and common
tansy. It is also interesting to note that spotted knapweed was observed increasingly
often in common tansy areas, post all treatments. This indicates that once that
particular niche was opened by the removal of common tansy, spotted knapweed was
able to quickly colonize in those areas. It may be possible that spotted knapweed seed
is lying dormant in areas already colonized by common tansy. This could result in an
undesirable secondary arrest in the attempted direction of the successional pathway.
Vegetation surveys indicate that during the following summer post treatments,
overall numbers of species were reduced. These surveys also show that many of the
species that were recorded post treatments were non-native themselves. This would
not be a desired outcome in a management situation. However, prairie species are
often time perennial and have large root structures. It can take three to 5 years to see
these species reemerge after disturbance, regardless if it is unintentional disturbance or
directed disturbance. Additional years of survey need to be conducted.
76
The data presented in this thesis is a testament to the tenacity and persistence
of spotted knapweed and common tansy. Once it was observed that these two species
increased in percent cover in the 2011 emergent stand data collection, the decision was
made to incorporate a fourth factor in the form of the selective herbicide, Milestone.
This decision resulted from the primary purpose of my thesis project which was to
provide Camp Ripley the means to reduce invasive plant species throughout the 20000
ha training site. The selective herbicide did significantly reduce the presence of both
spotted knapweed and common tansy. However it also reduced species richness in
plots and promoted the growth of non-native grasses. Future data collection is
recommended to observe forb recovery in the sites treated with Milestone. Another
negative aspect pertaining to the application of selective herbicides is that they are
costly and can result in populations of herbicide resistant weeds. The cost-efficiency
of certain combinations of treatments can be used as a measure of the efficiency of
restoration activities. Different combinations of treatment options produce different
results in restoration effectiveness. Over time, the directed disturbance that was done
in the form of altering site availability, species performance, and species availability
should lend itself to the general process of succession. This reduces the need for
continued interference and continued input of costs. Efficiency and effectiveness of
any restoration can benefit from the results of this study, whether or not invasive
percent cover is decreased. If it is not cost-effective or feasible to reduce these two
invasive species using the methods employed in this study, continued data collection
and analysis will state this conclusively.
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77
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APPENDIX
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90
SUPPORTING SOURCES FOR THE STUDY
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