EFFECT OF HIGH-INTENSITY DIRECTED FIRE IN DIFFERENT SEASONS
ON SURVIVAL AND SPROUTING OF THREE INVASIVE SPECIES:
LONICERA SPP (BUSH HONEYSUCKLE), PAULOWNIA TOMENTOSA (ROYAL
PAULOWNIA), AND LIGUSTRUM SINENSE (CHINESE PRIVET)
by
JEANETTE ROCHELLE WILLIAMS
A THESIS
Submitted in partial fulfillment of the requirements
for the degree of Master of Science
in the Department of Biological and Environmental Sciences
in the School of Graduate Studies
Alabama A&M University
Normal, Alabama 35762
November 2011
Submitted by JEANETTE ROCHELLE WILLIAMS in partial fulfillment of
the requirements for the degree of MASTER OF SCIENCE specializing in PLANT
AND SOIL SCIENCE.
Accepted on behalf of the Faculty of the Graduate School by the Thesis
Committee:
____________________________ Major advisor
____________________________
____________________________
____________________________
____________________________ Dean of the Graduate School
____________________________ Date
ii
Copyright by
JEANETTE ROCHELLE WILLIAMS
2011
iii
This thesis is dedicated to my loving and supporting family and friends.
iv
EFFECT OF HIGH-INTENSITY DIRECTED FIRE IN DIFFERENT SEASONS ON
SURVIVAL AND SPROUTING OF THREE INVASIVE SPECIES: LONICERA SPP
(BUSH HONEYSUCKLE), PAULOWNIA TOMENTOSA (ROYAL PAULOWNIA),
AND LIGUSTRUM SINENSE (CHINESE PRIVET)
Williams, Jeanette R., M.S., Alabama A&M University, 2011. 82pp.
Thesis Advisor: Dr. Luben Dimov
Invasive plant species are widely recognized as a serious problem. The
introduction of non-indigenous species to new habitats has been primarily through human
influence. Non-indigenous species can cause local extinction or a vast decline in some
native species populations by increasing competition, as well as reducing biodiversity
through modifications of their habitat. The control measures currently used to manage
invasive species commonly involve herbicides that can be toxic to other plants, people,
and wildlife, such as reduction of nutrients to non-target species, mortality in tadpoles,
deformation of fish, and reduced fertility and sexual development in frogs. There is a
need for new methods for ecological restoration through the removal of invasive species
that do not use herbicides but are similarly efficient to herbicide-based methods. In this
study royal paulownia and Chinese privet were divided into two diameter size classes that
were burned for two different lengths of time using a propane-powered torch.
Honeysuckle was burned for the same length of time and all species were burned during
three seasons. Greatest mortality occurred for paulownia when treatments were applied in
summer and when burned for 30 s in diameter size class 3.8 cm to 20.1 cm and when
burned for 60 s in diameter size class 20.2 cm to 68.6 cm. The greatest mortality for
Chinese privet and honeysuckle occurred in spring and summer. No differences occurred
v
in mortality for Chinese privet stems burned for the various lengths of time in either
diameter size class.
Keywords: Invasive, Paulownia tomentosa, Ligustrum sinense, Lonicera, mortality,
sprouting, burn
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TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION ........................................................................................ 1
Objectives .......................................................................................................................... 3
Justification ........................................................................................................................ 3
Literature Review............................................................................................................... 5
Health Risks of Herbicide Use........................................................................................ 5
Concerns with Prescribed Fire ........................................................................................ 8
Problems with Mechanical Control .............................................................................. 11
Difficulties with Grazing .............................................................................................. 12
Risks with Biological Control....................................................................................... 13
The Dilemma with Soil Solarization ............................................................................ 13
Species of Study............................................................................................................ 14
Bush honeysuckle ......................................................................................................... 14
Chinese privet ............................................................................................................... 16
Royal paulownia ........................................................................................................... 18
CHAPTER 2 MATERIALS AND METHODS ............................................................... 21
Study Site ...................................................................................................................... 21
Experimental Design and Sampling ............................................................................. 22
Hypothesis and Statistical Analysis .............................................................................. 29
CHAPTER 3 RESULTS ................................................................................................... 31
Mortality and Sprouting of Honeysuckle after One Growing Season .......................... 31
Mortality and Sprouting of Honeysuckle after Two Growing Seasons ........................ 34
Mortality and Sprouting of Chinese Privet after One Growing Season ....................... 37
Mortality and Sprouting of Chinese Privet after Two Growing Seasons ..................... 44
Paulownia Mortality ..................................................................................................... 44
Paulownia Sprouts ........................................................................................................ 48
CHAPTER 4 DISCUSSION……………………………………………………………..54
Conclusion ..................................................................................................................... 60
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LIST OF TABLES
Table
Page
Table 2.1
Treatment design for each season, year, and burn time of honeysuckle…23
Table 2.2
Dates when treatment response data was collected for honeysuckle.........24
Table 2.3
Treatment design for each season, year, diameter class, and burn time
of privet…………………………………………………………………..26
Table 2.4
Dates of treatments and when data was collected from 2010 to 2011
for privet………………………………………………………………….26
Table 2.5
Paulownia treatment design……………………………………………...28
Table 3.1
Percent mean mortality and standard error in the control and 5 s burn
for honeysuckle……………………………………………………..……32
Table 3.2
Difference in plant mortality after burning in different seasons for
honeysuckle…………………………………………………………........33
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Table 3.3
Standard error and average number of sprouts per plant in the control
and 5 s burn for each season in honeysuckle.............................................34
Table 3.4
Difference in the number of sprouts per plant one growing season
after burning in the winter, spring or summer and no burning for
honeysuckle comparisons......................................................................... 34
Table 3.5
Difference in honeysuckle mortality after burning during
different seasons.........................................................................................35
Table 3.6
The difference in the number of honeysuckle sprouts per plant two
growing seasons after treatment.................................................................35
Table 3.7
The differences in the average percent mortality after 30 s and 40 s
burn treatments (combined) after one and two growing seasons for
privet……………………………………………………..........................38
Table 3.8
Percent mean mortality and standard error in the small and large diameter
classes of Chinese privet after one and two growing seasons...................40
Table 3.9
The differences in number of sprouts per plant for the 30 s and 40 s
treatments (combined) after treatment (control, winter, spring, and
summer burn) for privet ………………………………………………....41
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Table 3.10
Average number of Chinese privet sprouts per plant and standard error
in the small and large diameter classes after one growing season.……....42
Table 3.11
Differences in sprouts per plant when burned for 5 s or 10 s for privet....43
Table 3.12
Difference in number of privet stump sprouts between plants burned in
winter 2010 (whose sprouts were burned in August 2010) and plants
burned in winter 2011 (whose sprouts were not burned), analogous for
spring …………….....................................................................................43
Table 3.13
Percent of tree mortality and standard error in August of 2011 for
treatments applied in winter, spring, and summer of 2010 for
paulownia………………………………………………………………...45
Table 3.14
Effect of burning paulownia for different lengths of time during all
seasons combined on percent mortality, compared to the control and
among the various burn lengths for small and large diameter
classes……………………………………………………………………46
Table 3.15
Effect of burning paulownia for different lengths of time during the
seasons: winter, spring, and summer on percent tree mortality in the
x
small and large diameter classes:………………….……………………..47
Table 3.16
The effect of burning paulownia percent mortality when burning for
different seasons and burn lengths (s) of: 15, 30, 40, and 60 s …….……49
Table 3.17
Mean percent and standard error of paulownia trees with stump sprouts
in each treatment…………………………………………………..…..…49
Table 3.18
Effect of burning on the percent of paulownia trees with new stump
sprouts when the main stem was burned for different lengths of time
during all seasons combined compared to the control and other burn
lengths………….………………………………………………………...50
Table 3.19
Effect of burn length in different seasons on the percent of paulownia
trees with stump sprouts …...……………………………….……………51
Table 3.20
The effect of burning on stump sprouts when the main paulownia stem
is burned, during different seasons and burn lengths (s) 15 s, 30 s, 40 s,
and 60 s……………………………………………..…………………....52
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LIST OF FIGURES
Figure
Figure 3.1
Page
Percent mean mortality and standard error of honeysuckle after one
and two growing seasons...........................................................................32
Figure 3.2
Average number of sprouts per honeysuckle bush and standard error
after one and two growing seasons............................................................33
Figure 3.3
Average number of honeysuckle sprouts per plant and standard error in
August 2011 one growing season after treatment. The same letters indicate
no difference at the p<0.1 level…………….……………...........36
Figure 3.4
Percent mean mortality and standard error in Chinese privet after one
and two growing seasons in the small diameter size class ……...…...…..37
Figure 3.5
Percent Mean Mortality and standard error in Chinese privet after one
and two growing seasons in the large diameter size class.........................39
Figure 3.6
Average number of sprouts and standard error of Chinese privet after
one and two growing seasons in the small diameter size class…………..40
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Figure 3.7
Average number of Chinese privet sprouts per plant and standard error
after one and two growing seasons in the large diameter size
class……………………………………………........................................41
Figure 3.8
Paulownia mean percent mortality and standard error in the small
diameter class after a 15 s and 30 s burn.…………. ……………………46
Figure 3.9
Paulownia mean percent mortality and standard error in the large
diameter class after a 40 s and 60 s burn.…………………………. ……47
Figure 3.10
Mean percent and standard error of small diameter paulownia trees
with sprouts after burning for 30 s in winter, spring, and summer………52
Figure 3.11
Mean percent and standard error of large diameter paulownia trees
with sprouts after burning for 60 s in winter, spring, and summer.…. ….53
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CHAPTER 1
INTRODUCTION
Most non-native species were brought into this country for forage or for
ornamental purposes, while others were brought here accidently (Miller J.H. 2003).
Invasive woody species are of growing concern because of the negative impact they have
on ecosystems (Burton et al. 2005). Invasive species lack their main natural predators that
help to control their population and thus have greater survival than indigenous species
(Miller J.H. 2003). Non-native species are problematic when they become invasive
because they hinder forest use and management activities, reduce biodiversity and
wildlife habitat (Miller J.H. 2003). In order to restore indigenous species in our
ecosystems, non-native species need to be removed or at least controlled.
Invasive species rank second as a threat to biodiversity of imperiled groups of
plants, mammals, invertebrates, fish, reptiles, and amphibians after habitat destruction
(Wilcove et al. 1998). Other threats include overharvest, pollution, and diseases (Wilcove
et al. 1998). Species such as Chinese privet invade cultivated landscapes, disturbed areas,
and wildlands where they form dense thickets and outcompete native vegetation (Batcher
2000).
Not only do invasive species pose a threat to biodiversity and increase
competition, but they are also economically expensive to control once established. The
1
detrimental effects from invasive species are estimated to cost $138 billion/year in the
United States (Pimentel et al. 1999). There is no direct way to assign monetary value to
all the effects such as extinctions, losses in biodiversity, ecosystem services, and
aesthetics and so this estimation of costs per year is an approximate and conservative
estimate of the losses, damages, and cost of control (Pimentel et al. 1999).
There are numerous management techniques for control of unwanted woody
species which include herbicide use, mechanical control, prescribed fire, grazing,
biological control, and soil solarization (Green and Newell 1982, Hartman and McCarthy
2004, Miller 2003, Tu et al. 2001). Of these methods the use of certain herbicides poses
many negative effects on human health and the environment. These toxic effects can
cause reduction of nutrients to non-target species, mortality in tadpoles, deformation of
fish, reduce fertility and sexual development in frogs, and negatively impact human
placental cells (Richard et al. 2005) among many other negative effects. Less toxic
control measures are expensive to apply and less effective. The method of control tested
used high-intensity directed fire at the base of each plant stem, is a more environmentally
friendly and possibly a more cost effective technique of controlling invasive species.
Unlike prescribed burning, this method requires one worker instead of a full crew, does
not require the use of expensive fire control equipment (e.g. bulldozers), and can be
applied anytime when there is no risk of starting a wildfire (i.e. it can be applied during
or soon after rain, snow, or when humidity and moisture are high).
2
Objectives
The objective of my study was to find a new management technique that poses minimal
risks to the environment and is effective at controlling the spread of invasive woody
species by
1. Examining the effectiveness of high-intensity fire directed at the base of the stem to
kill and prevent stump resprouting in three non-native invasive plant species; royal
paulownia (Paulownia tomentosa (Thunb.) Siebold & Zucc. ex Steud.), Chinese privet
(Ligustrum sinense Lour.), and bush honeysuckle (Lonicera spp);
2. Examining the effectiveness of the treatments when they are applied in different
seasons (winter, spring, and summer);
3. Comparing the effectiveness of the treatments for different burn time lengths.
Justification
There are many methods used for controlling invasive species which include
mechanical control, herbicidal control, prescribed burning, grazing, biological control,
and soil solarization. Each control method comes with its advantages and disadvantages.
Herbicide use, prescribed fire, and mechanical control are among the most common
control methods.
The average yearly amounts of herbicide used in forestry over a period of a
rotation are much smaller than in agriculture. Nevertheless, use of some herbicides has
many known and potential negative health effects to humans and wildlife, and it
contaminates the environment (Neumann et al. 2006, Acquavella et al. 2004). Some of
the most commonly used herbicides are glyphosate-based. The toxicity of the active
3
ingredient and especially of the inactive ingredients, adjuvants, and surfactants are now
well known and documented (Peluso et al. 1998). Other herbicides are less extensively
studied, but it is possible that as studies accumulate, toxicity effects may become known.
There are major disadvantages when implementing a prescribed burn such as air
quality and visibility. Other disadvantages include the lack or excess of fuel on the forest
floor. Fire may have been suppressed for so long that the fuel buildup is very large and a
prescribed fire will burn too intensely and cause mortality in desired species (Stephens
and Ruth 2005). It can indiscriminately kill non-target native species even at low
intensity and often stimulates vigorous sprouting from the invasive species (Heffernan
1998). This method of control requires a crew of qualified personnel, expensive
equipment, construction of fire breaks, and poses harmful risk to property and human life
(Hanby 2005) which raises liability and public concern (McCaffrey 2006).
Mechanical control methods are expensive, generally ineffective (Tu et al. 2001)
and often disturb the soil (Evans et al. 2006). This type of control has many advantages
but is often time-consuming and not as effective when used without other measures of
control such as herbicide application or burning (Miller 2007).
Three of the most common invasive species of the southeast that impact forests
are Chinese privet, royal paulownia, and bush honeysuckle. Each of these species has
similar characteristics that influence their ability to spread quickly, particularly in
disturbed areas. Control methods for all three species vary because of their different
biological characteristics. A more environmentally friendly control method needs to be
sought. More effective control methods need to be developed that can work as well as
herbicides, but are safer for the applicators and to the environment. The type of burning
4
tested may be just one such method. In this study high intensity fire was used, directed at
the base of the stems that is aimed at causing above ground plant mortality and reduction
in stump sprouting.
Literature Review
Although there are many methods to control unwanted vegetation, each method
listed above either has risks for damage to non-target species, is time consuming, labor
intensive, or expensive to apply. Application of herbicides is one of the most common
control methods practiced currently, often along with some of the more environmentally
friendly methods. Some of the main problems with the application of herbicides involve
the health risks to wildlife and humans.
Health Risks of Herbicide Use
Some of the commonly used herbicides in forestry have been glyphosate
formulations commercialized as Roundup® by the Monsanto Company. Its active
ingredient has been detected in urine of applicators whether or not prevention was taken
to minimize herbicidal contact (Acquavella et al. 2004). Glyphosate is often found in
non-target plant species after application (Neumann et al. 2006). When glyphosate is
applied to the target species, some of the overspray makes it to the rhizosphere where
surrounding plants are affected, and ultimately the non-target species ability to absorb
adequate nutrients is reduced. In addition to impacting negatively some non-targeted
plants, glyphosate can be harmful to microorganisms and animals as well (Neumann et al.
2006).
5
Evidence for toxicity of the Roundup® formulations has been accumulating in the
literature. Work by Peluso et al. (1998) demonstrated that Roundup® induced a dosedependent formation of DNA adducts (a complex that forms when a chemical binds to
the DNA) in the kidneys and liver of mice. The formation of such adducts in the organs is
considered as damage to the DNA. The DNA adducts were related to some unknown
compound in the mixture rather than to the active ingredient, isopropylammonium salt of
glyphosate.
A study on a coastal microbial community showed that Roundup® modifies
natural coastal microbial communities of prokaryotes and some pico-eukaryotes after a 7day exposure (Stachowski-Haberkorn et al. 2008). Relyea (2005) showed that Roundup®
and its surfactant POEA (Polyoxiethyleneamine) affect amphibians causing high
mortality rates. Within three weeks 98% of tadpoles were killed, and within 24 hours
79% of juvenile frogs and toads were killed. This study was designed to research what
could happen when an herbicide was applied in a worst case scenario, at levels a bit
higher than what is found in nature (3.8 mg of AI/L).
Roundup® affects young and adult tilapia approximately after 96 hours of
exposure (Jiraungkoorskul et al. 2002). The gills were found to have filament cell
proliferation (a chain-like series of cells increasing at a fast rate), lamellar cell
hyperplasia (abnormal increase of cells in the scale layer), lamellar fusion, epithelial
lifting (tissue composed of many cells causing a thickness in the scale layer), and
aneurysm. There was vacuolation of hepatocytes (cells involved in protein synthesis were
enlarged) and nuclear pyknosis (nucleus degenerative state) in the liver. Kidney lesions
consisted of dilation of Bowman’s space and buildup of hyaline droplets in the tubular
6
epithelial cells. This study showed clearly that the presence of Roundup® causes
degenerative formation of organs in tilapia.
Roundup® also disrupts the expression of the steroidogenic acute regulatory
(StAR) protein, inhibits steroidogenesis, and causes decrease in progesterone production
(Walsh et al. 2000). Progesterone is a steroid hormone involved in the female menstrual
cycle, pregnancy (by supporting gestation) and embryogenesis of animal species and
humans. Therefore, Roundup® can impact fertility in wildlife and humans. Work by
Paganelli et al. (2010) demonstrated Glyphosate and Glyphosate based herbicides (GBH)
impair the mechanisms needed in regulating early development in frog and chicken
vertebrate embryos when exposed at sub lethal levels, which leads to concerns about how
this may affect human offspring when exposed to GBH.
Glyphosate is also toxic to human placental JEG3 cells and this toxicity was
observed less than 18 hours after treatment (Richard et al. 2005). More importantly, this
toxicity occurred at concentrations lower than the concentrations found in agricultural
use. The observed toxic effect went up with the increases in concentration as well as in
the presence of Roundup adjuvants. Moreover, the toxicity of Roundup is always more
detrimental to the human placental cells than Glyphosate alone (Richard et al. 2005).
Herbicide is applied in various ways such as by injection (herbicide is injected
with a specialized hatchet or is sprayed inside a freshly made cut around the stem),
through cutting of the stem then application on the cut surface, or through spraying of the
bark at the base of an uncut targeted plant (Bartlow et al. 1997, Miller 2003, Hartman and
McCarthy 2004). The continued use of herbicides has led to more research on their
adverse effects, and thus the producers have responded by manufacturing herbicides that
7
are less toxic and better suited for targeted species than previously (Hobbs and
Humphries 1995). A problem with herbicide use is that over time the local population of
the targeted species being treated may decline, but this can leave room for other invasive
species not affected by the herbicide to establish (Ditomaso 2000, Groves 1989). This
however, is a concern with all methods for control. Another problem is that targeted
species may evolve resistance to a particular herbicide, thus further enhancing the
problem of controlling the invasive population (Ditomaso 2000). Herbicide use is also
less desirable in valued natural areas and is not used as widely as in agricultural areas
(Groves 1989). Additionally, repeated application of herbicides to a targeted species may
be required, as it is more effective than a single application (Paynter and Flanagan 2004).
Other disadvantages of chemical application are the economic cost for continued
application, contamination of soil and surface water, and effects of non-targeted species
(Masters and Sheley 2001). My technique for invasive control does not cause detrimental
effects to humans, the environment, or wildlife as do herbicides.
Concerns with Prescribed Fire
Although prescribed burning is being used with increased frequency as a
management tool to reduce fuel buildup, minimize natural fire severity, control some
invasive species, and restore landscapes to a more historic plant community, it has some
constraints. They include the fact that fire burns indiscriminately, involves risks to
property and life, and requires the presence of highly-trained insured personnel and
possibly heavy equipment, which increases the cost. Another constraint is fire’s
undesired use in ecosystems inhabited by certain threatened or endangered species. The
8
application of a prescribed burn in an area with a large fuel load would increase fire
intensity which may affect the viability of certain threatened or endangered species in
that area, if the fuel load was not reduced around such desired species prior to the burn
(Stephens and Ruth 2005).
Prescribed burns are a common management tool used to remove undesired
species to increase favored species productivity by decreasing competition. The type of
exotic species a prescribed burn can help to control depends on the species characteristics
such as for example whether they are capable of sprouting from the root collar or the
roots. Invasive species that sprout back poorly after fire are good candidates for control in
this manner (Keeley 2006), but only if the native species that is being restored has a
greater fire tolerance. The Bromus japonicus (Japanese brome), Acroptilon repens
(Russian knapweed), and Euphorbia esula (leafy spurge) seed bank is greatly reduced by
burning (Vermeire and Rinella 2009). Annual prescribed burning successfully reduces
Scot’s broom cover (Tveten and Fonda 1999). On the other hand, species such as garlic
mustard and Chinese lespedeza are stimulated by fire (Heffernan 1998). The use of
prescribed burns also raises public concerns such as smoke, liability, and fire control. The
public must trust the persons or agency performing the burn and have an understanding of
why it is being performed (McCaffrey 2006). Prescribed burning may not be as beneficial
to small land owners or managers because of the person-power needed and safety issues
that may arise during a burn (Heffernan 1998).
There are various patterns for ignition of a prescribed burn which include
backing, heading, flanking, strip head, spot, ring, center, and chevron. Some patterns of
ignition are more intense than others. For instance a backing fire burns against the wind,
9
and thus burns at a slower rate causing a longer burning duration to occur on vegetation
(Hanby 2005). The problem with this pattern of ignition in terms of trying to control
invasive species that are prone to resprout after a disturbance is that this pattern burns
less intensely and may not be able to effectively kill or harm the roots or basal buds of
unwanted vegetation. A center pattern of ignition on the other hand burns more intensely
and so requires more help to make sure the fire does not get out of hand, produces more
smoke, and has a faster rate of spread (Hanby 2005). Although the heat is more intense
this pattern of ignition passes over vegetation too quickly and may not effectively
penetrate through the cambium layers of woody vegetation to cause mortality and may be
inefficient at heating up basal buds or the roots to prevent resprouting.
My proposed method of control works quite differently than a prescribed burn.
Used was a propane-powered torch, while the most common tool used in prescribed
burning is a drip torch and the ignition fuel is a mixture of gas and diesel fuel (Hanby
2005). A prescribed burn is used primarily to burn large areas of land, whereas my
method is used to burn critical parts of individual plants and the main goal is to only
cause mortality in the unwanted invasive plants with no adverse effects on native species
or the environment. The amount of smoke produced by a prescribed burn is much greater
than what is produced under my management technique. Prescribed burning is limited in
its use by humidity, temperature, fuel load, wind speed, urban areas, drought, and
uncertified managers, whereas my technique is not limited by these factors.
10
Problems with Mechanical Control
Mechanical control can include an array of techniques such as: hand pulling,
uprooting using various types of tools, cutting, mowing, girdling, mulching, and tilling.
Hand pulling or pulling with a tool is practical in small areas or in sensitive areas where
herbicides cannot be applied. The hand pulling type of mechanical control is labor
intensive. Other tools are difficult to use in dense areas, and there are risks to spreading
the undesired species to other locations if equipment is not cleaned properly (Tu et al.
2001). Mechanical control is also size limited: mature woody species are too large to be
removed in this manner. In such cases mowing (Heffernan 1998) or hand felling by a
chainsaw (Akerson et al. 2000) may have to be applied instead.
Many invasive species quickly establish in a landscape after a disturbance (Sheley
et al. 1996) and mechanical methods can cause disturbance to the forest floor by exposing
the soil, increasing light availability, removing native vegetation, and damaging roots of
native species (Evans et al. 2006). Mechanical control can also be expensive to apply in
dense stands and difficult to use in rocky and harsh landscapes (Wilgen et al. 2001).
Girdling is a process where a tree is cut around the circumference of the stem
down through the cambium layer to prevent vascular transmission of water and nutrients.
It is an alternative method to herbicide application but is restricted to larger woody
species and may stimulate sprouting (Bartlow et al. 1997).
Mulching is the addition of hay, wood chips, grass clippings, or even newspaper
to the ground in order to cover seeds or seedling and prevent sprouting or stop growth.
This method is most beneficial in control of annual species; perennial species have too
much carbohydrate storage in the roots and can sprout through the mulch.
11
Tilling is the process of turning soil and cutting root systems where unwanted
vegetation grows. It works best on annuals. Tilling disturbs the soil and is limited in its
use to areas that are already disturbed (Tu et al. 2001). Although tilling can minimize
seed germination (Heffernan 1998) it is not effective on species such as Microstegium
vimineum a Japanese grass (Akerson et al. 2000, Evans et al. 2006).
Mechanical methods are usually not the only method applied for control, but are
instead combined with other methods such as herbicide application (Miller 2007).
Mechanical control is generally not effective at eradication without the use of other non
mechanical control methods. My method of control does not pose risk of spreading the
undesired species, does not cause disturbance to the forest floor, is less expensive than
mechanical methods, and is more effective on perennial species.
Difficulties with Grazing
Goats consume a larger variety of vegetation than other livestock. A problem with
this method is goats are capable of also consuming non-targeted vegetation (Green and
Newell 1982). Goats will consume species such as multiflora rose but after grazing this
species sprouts back (Luginbuhl et al. 1996), indicating that grazing alone may not
eradicate a local population of undesired species, unless grazers are kept there for much
longer periods of time. Grazing must continue for years in order to maintain undesired
species at low local population levels (Cohen et al. 2008) which can become time
consuming to a land manager. Additionally, the goats will damage desired species as
well.
12
Risks with Biological Control
A key reason why invasive species are so successful at establishing themselves in
a new habitat and outcompeting native species is because, they do not have their natural
predators or pathogens to keep their population numbers in check. Biological control is a
method where the invasive species native predators are brought from their natural habitat
and placed in the same area that the invasive species colonized. The theory that biological
control will effectively control an invasive species does not stand true for all species.
Agapeta zoegana, a knapweed root moth was introduced in an area where Centaurea
maculosa (spotted knapweed) grew. The hypothesis was that the native grass species
Festuca idahoensis would be stimulated to grow after the introduction of A. zoegana on
C. maculosa. Plots where C. maculosa was attacked by the moth, however, showed more
of a negative impact on the native grass F. idahoensis than in plots where the moth was
not introduced. It is believed that this indirect effect could have happened because C.
maculosa was attacked, this could have stimulated it to grow more rapidly, or it could
have responded by increasing its allelopathic productivity as some plants do when they
are stressed (Callaway et al. 1999). Biological control agents introduced to a new region
are also exotic species that can become invasive and pose predatory threats to native
species. Biological control methods also require a vast amount of research on their
possible effects on the environment before application can legally be accomplished.
The Dilemma with Soil Solarization
Soil solarization is a procedure where clear or black plastic is placed over the soil
to heat the soil to temperatures that cause mortality in plants, seeds, pathogens and insects
13
(Tu et al. 2001). Invasive species seed viability is reduced by this method when applied
in summer months on Acacia saligna, A. murrayana, and A. sclerosperma (Cohen et al.
2008). This method has been shown to help reduce competition for moisture and cause an
increase in tree height in peach and walnut trees (Stapelton and DeVay 1982). Although
this method is less harmful because no chemicals are used to effectively reduce unwanted
species, soil solarization alters soil properties which can last up to two years and
ultimately affect native species (Cohen et al. 2008), is expensive and labor intensive.
Species of Study
Chinese privet, bush honeysuckle, and royal Paulownia are three common
invasive woody plant species in the North Alabama region, but are also found throughout
the South (Miller 2003). Invasive species have the ability to grow in a vast array of
landscapes and tend to cover a larger range of area than native species because they can
more easily adapt to new areas (Goodwin et al. 1999). This increases the chance of them
accidently being picked up and transported to new landscapes.
Bush honeysuckle
The exact species of the non-native bush honeysuckles can be difficult to identify
in the field, but all are invasive and all have the same control methods (USDA Forest
Service 2005). Herman and Davidson (1997) studied 135 Lonicera taxa and their
susceptibility to aphids and reported that honeysuckle species hybridize freely, and that it
can be difficult to determine the true types of honeysuckle. Barnes and Cottam (1974)
studied similarities in morphology and physiology of Lonicera X bella, Lonicera tatarica
14
and Lonicera morrowi based on previous literature and mentioned that there may have
been uncertainty in the identification of the taxa involved. For this study the type of
honeysuckle where treatments are applied will be referred to simply as Lonicera. Most
Lonicera species are native to Asia (TNEPPC 2010). Honeysuckle is a deciduous shrub
that can reach up to six meters in height and is slightly shade tolerant (Luken and Thieret
1996). It has multiple stems, opposite leaves (Miller 2007), and a shallow root system
(Hutchinson and Vankat 1997). Leaves of honeysuckle emerge before native species in
the spring and remain on the bush for a longer period of time after native species have
dropped their leaves (McEwan et al. 2009), indicating that this species can
photosynthesize before light becomes a limiting factor under a hardwood canopy in the
spring, and continue photosynthesis after fall. Leaves of this species are also more freeze
tolerant than native species (McEwan et al. 2009). Seeds remain in the soil for long
period of time and colonization occurs by seeds, root sprouts (Miller 2007), or stump
sprouts (Ingold and Craycraft 1983).
Honeysuckle is listed as an exotic species that poses severe threat to native plant
habitat (Kentucky Exotic Pest Plant Council 2008). Honeysuckle is a major problem in
forested areas because it causes a decrease in species richness under its crown (Collier
and Vankat 2002). Its cover is related to the time since invasion (Hutchinson and Vankat
1997), the more time honeysuckle has to grow in an area the more native species richness
and tree seedlings abundance decline (Collier and Vankat 2002). It inhibits germination
in seeds of neighbors through its allelopathic leaves and roots (Dorning and Cipollini
2005). The removal of the above ground portion of honeysuckle increases native specie
diversity (Gorchov and Trisel 2003).
15
Honeysuckle’s ability to invade a space is greatly influenced by the amount of
light that is available, and it is a major competitor in open areas (Luken and Mattimiro
1991). The more light the greater number of the invasive shrub, which may be why there
are not as many honeysuckle shrubs in late successional forests (Hutchinson and Vankat
1997). Its invasiveness has much to do with its ability to resprout after a single cutting
possibly due to carbohydrate storage in the roots (Luken and Mattimiro 1991). Its
invasiveness is also due to the dispersal of honeysuckle seeds by birds and other animals
(Miller 2007).
There are many methods to control honeysuckle: cut-and-paint method (Cipollini
et al. 2009, Hartman and McCarthy 2004), stem injection (McCarthy 2004), basal
application of herbicides, mechanical control (Cipollini et al. 2009), or foliar spray with
herbicide (Miller 2007). There is a greater response to stem injection than to the cut-andpaint method (Hartman and McCarthy 2004), and there is a greater response to the basal
application of herbicides than to the cut-and-paint method (Cipollini et al. 2009).
My research may help to reduce the amount of herbicide used by introducing a
simple, more environmentally friendly and safer management technique for controlling
non-native vegetation. My study and practice of smaller scale fire management
techniques avoid the concerns related to regular prescribed fire efforts.
Chinese privet
Chinese privet (Ligustrum sinense) is a perennial shrub (Bartlow et al. 1997) or
tree (Urbatsch 2010) that can reach 9 meters in height and belongs to the Oleaceae family
16
(Bartlow et al. 1997). It was introduced into the United States in 1852 from China and is
used as an ornamental (Urbatsch 2010). This species can be found in the southeastern
United States (Miller 2007, Batcher 2000) usually in floodplains or disturbed areas
(Drake et al. 2003). It grows from a seed, stump (Bartlow 1997), or root sprout (Miller
2007), and is a common food source for deer (Batcher 2000) and birds (Drake et al.
2003).
Chinese privet has been listed as the third most problematic invasive species by
the United States Department of Energy Oak Ridge National Environmental Research
Park of Oak Ridge, Tennessee (Drake et al. 2003). Problems associated with Chinese
privet include its ability to reduce diversity in riparian communities which in turn can
affect the natural function and importance of the native riparian woody species (Burton et
al. 2005). The removal of this species greatly increases beetle diversity (Ulyshen et al.
2010) and bee diversity (Hanula and Horn 2011). Chinese privet is capable of capturing
more light because of its larger height and leaf area compared to native shrub species
(Morris et al. 2002). Fruit production in Chinese privet is ten times greater than fruit
production of the native species upland swamp privet (Forestiera ligustrina) in high light
conditions, and has five times greater fruit production in low light conditions (Morris el
al. 2002).
The continuous spread of this species is mainly caused by anthropogenic
processes such as urbanization and road construction. Chinese privet has reduced
diversity closer to urbanized areas (Burton et al. 2005). More exotic shrubs grow closer to
roads while the amount decreases further from roadsides (Flory and Clay 2005). Birds eat
17
the fruits of privet and further enhance its ability to spread by dispersing the seeds (Drake
et al. 2003).
Biological control methods are being tested to control this species. One example
is a Chinese adult leaf-mining beetle (Argopistes tsekooni), which feeds on the leaves.
The females deposit their eggs on privet and when the larvae hatch they mine through the
leaf by eating the leaf tissue. Further research is needed to determine the effects this
control method could have in the United States (Zhang et al. 2008). Foliar applications of
herbicide using glyphosate formulations help to control this species when applied in the
spring and/or fall (Harrington and Miller 2005). Mechanical treatments such as hand
felling or mulching are other control methods currently used (Hanula et al. 2009).
Prescribed burns have been applied, and have reduced privet biomass but this method
alone could not reduce this species over a longer period of time (Faulkner et al. 1989).
Many of these control methods are not used alone but rather combined to have a greater
effect.
Royal paulownia
Royal paulownia is a tree native of China belonging to the Scrophulariaceae. It is
a fast growing invasive species here in the United States that reaches heights of 20.0
meters and diameters of 0.6 meters (Knopf 2003). It is capable of growing up to 5.0
meters in one year, and reproduces from seeds, root sprouts (Bartlow et al. 1997), or
stump sprouts (Miller 2007). Paulownia can invade a variety of different habitats
including roadsides, cliffs, riparian areas, open woods, highway embankments, stream
18
banks, forest edges, landslides, burned-over areas, rocky-outcroppings, mine spoils, old
home sites, and other disturbed sites (Evans et al. 2006).
Royal paulownia was ranked as the twelfth most problematic invasive species by
the National Environmental Research Park (Drake et al. 2003). Paulownia infestations
occur in scattered and localized areas of Alabama in managed forests as well as natural
areas and parks (Alabama Invasive Plant Council 2007). It is an undesirable species
because it causes management problems (Drake et al. 2003) such as difficulty for
managers to establish fire adapted species like table mountain pine (Pinus pungens),
because paulownia’s ability to quickly establish itself after a disturbance such as a fire
(Evans et al. 2006).
This species is wide-spread because it produces an abundance of seeds, (Drake et
al. 2003), estimated to be up to 20 million per plant (Remaley 2005) that are small
lightweight and easily spread by wind or water. The seeds can germinate quickly when in
contact with mineral soil (Remaley 2005) and seeds remain viable in the soil for many
years (McCarthy 2005). Paulownia’s continued use as an ornamental, for wood
production (Miller2007), and mined land reclamation (Zhao-hua 1986) has increased its
opportunity to spread and outcompete native species.
Mechanical control methods for paulownia seedlings include hand pulling. This
type of control should be done after a rain when the soil is moist and will increase the
chance of pulling the entire seedling out of the ground successfully (Alabama Invasive
Plant Council 2007). Cutting the entire tree down shortly after flowers bloom to reduce
seed production can control mature paulownia trees for a short time until resprouting
occurs (Bartlow et al. 1997). Herbicidal control using Arsenal AC* or a formulation of
19
glyphosate can be applied by stem injection into the main stem of mature trees (Miller
2007). Prescribed fire has not been successful in the removal of this species (Evans et al.
2006).
20
CHAPTER 2
MATERIALS AND METHODS
Study Site
The study for all three species was conducted in northeastern Alabama on
Alabama A&M University property. The bush honeysuckle site is located across Chase
Road to the east of Alabama A&M University campus, along a 422.0 meter trail
(34°47’00’’N, 86°33’32’’W) that runs through the property. The elevation is 259 m. The
honeysuckle site is predominately under a hardwood canopy and Juniperus virginiana
(eastern red cedar).
The study site for Chinese privet was at the Winifred Thomas Agricultural
Research Station (WTARTS), and located on the east side of a riparian zone at a length
of 722.0 m, and a west side of the riparian zone of 152.0 m (34°53’48’’N, 86°34’46’’W).
The elevation is 225 m. Samples were taken on the west and east side of the riparian
zone. This area is partially under a hardwood canopy and eastern red cedar.
The paulownia study site was at the WTARS in Hazel Green, Alabama
(34°53’51’’N, 86°34’25’’W). The elevation is 236 m. The paulownia trees were planted
approximately 20 years ago as part of a previous research project on agroforestry. The
trees were planted in rows along with Liriodendron tulipifera (tulip poplar), Quercus
rubra (red oak), and Carya illinoinensis (pecan).
21
Experimental Design and Sampling
In the honeysuckle study locations on Alabama A&M University property plots
were established along a path that runs the length of part of the property. To determine
plot locations random distances along the 422.0 meter path were generated. Ten random
distances were generated per season: winter - Feb/March, spring - April/May, and
summer - Aug in 2010 and winter - Jan/Feb and spring - April, for 2011. Once these
random distances were established, another random distance from 0.3 meters (the edge of
the trail) to 18 meters south of the path into the forest was generated. This is the distance
from the path to the plot center. After the plot center was determined, the nearest 20
plants from the plot center were chosen and flagged for treatment. The locations of the 4
control plots, each with ten plants per plot, were assigned randomly through the same
method along the 422.0 meter path. Control plots were selected once rather than each
season.
The honeysuckle stem diameter was chosen to be between 0.3 and 5.1 cm. This
particular diameter class was chosen because the stems on the vast majority of the bushes
were mostly within this size range. The upper diameter limit of 5.1 cm was chosen
because there were almost no stems larger than that, and therefore it would have been
hard to find enough for replication. The fire was powered using a torch (Red Dragon,
model: VT 3-30 C 500,000 BTU/HR) and a 7.0 kg propane tank. The burn time was
measured by verbal count. Two hundred plants were burned per season (winter, spring,
and summer) in 2010 and similarly in 2011 (winter and spring, but no summer, Table
2.1). Mortality was checked and analyzed after one growing season and similarly after
two growing seasons (Table 2.2).
22
Table 2.1. Treatment design for each season, year, and burn time of honeysuckle
Honeysuckle
Number
Number
Season of
replications
of plots
of plants
burn
Burn time (s)
burned
Control n=40 plants,
4
0
None
None
n=20 plants/plot
10
200
Winter 2010
5
n=20 plants/plot
10
200
Spring 2010
5
n=20 plants/plot
10
200
Summer 2010
5
n=20 plants/plot
10
200
Winter 2011
5
n=20 plants/plot
10
200
Spring 2011
5
10/plot
Sprouts were considered stump sprouts if they were at a distance of 0.64 cm or
less from the main stem. Any stem beyond that distance was considered a root sprout and
data for it was not collected. Stump sprouts that grew after the winter 2010 burn were
burned in May of 2010. Stump sprouts were not burned during any other season. Stump
sprouts were examined in July of 2010 for plants treated in April/May 2010, and then
examined again in August of 2010 before burning was to be applied to the sprouts.
Because many of the vigorous sprouts from July were either dead or dying by August,
sprouts were not burned to see if they would instead die out on their own.
Sprouting data from each seasonal burn in 2010 (winter, spring, and summer) and
the control, as well as each seasonal burn in 2011 (winter and spring) were included in
the analysis for the sprouts following one growing season from which treatment was
applied to the main stem/stems.
23
Table 2.2. Dates when treatment response data was collected for honeysuckle.
Parameter
Season and Date of Treatment Application
checked and time
Control,
Winter,
Spring,
Summer,
Winter,
since treatment
N/A
Feb/Mar,
Apr/May,
Aug, 2010
Jan/Feb, 2011 Apr,
2010
2010
Apr, 2010
Jul, 2010
Apr, 2011
May, 2011
Aug, 2011
N/A
May, 2011
Aug, 2011
N/A
N/A
Apr, 2010
Aug, 2010
Apr, 2011
May, 2011
Aug, 2011
N/A
May, 2011
Aug, 2011
Aug, 2011
N/A
Spring,
2011
Mortality
After 1 growing Jul, 2010
season
After 2 growing Apr, 2011
seasons
Sprouts
After 1 growing Aug, 2010
season
After 2 growing N/A
seasons
Note: N/A= mortality was not included in this analysis after the second growing season
of the winter 2010, 2011 burns, or after spring, 2011 burn.
Sprouting data from 1) spring, 2010, 2) summer, 2010, 3) control, and 4) winter, 2011,
were included in the analysis for the sprouts following the second growing season from
when treatment was applied to the main stem/stems (Table 2.2). A separate analysis was
conducted for the winter 2010 treatment whose sprouts were burned and compared to the
winter 2011 treatment whose sprouts were not burned.
Seven hundred twenty Chinese privet trees were treated, and an additional 40
trees served as the control. Before treatment the 720 trees and the 40 control trees were
divided into two diameter classes (based on the stem base diameter): 1.27-5.0 cm and
5.1-10.2 cm (Table 2.3). Five plots per season (winter, spring, and summer) in 2010 were
randomly selected along the riparian area. Three of the 5 plots were selected along the
east side of the 722.0 m riparian zone and 2 plots were selected along the west side of the
24
152.0 m riparian zone. Similarly 4 control plots were randomly selected along the
riparian area, 3 plots were selected along the east side and 1 plot selected along the west.
During 2011 the number of plots increased to 7 per season for winter and spring. Each
plot was randomly selected and 5 of the 7 plots were selected along the east side of the
riparian zone and 2 were selected along the west side. After random distances along the
stream were generated for both sides of the riparian zone, random distances to a plots
center headed west from the east side of the riparian zone and headed east from the west
side, were also generated.
Random distances from the edge of the riparian forest to the plot center ranged
from 0.5 m to 12.0 m, which is the approximate width of the riparian forest. Once the plot
centers were established the nearest 20 plants from the plot center were selected, ten of
each diameter class. Five trees with a diameter of 1.3-5.0 cm per plot were randomly
selected to be burned for 10 seconds and 5 trees for 20 seconds. Similarly, 5 trees with a
diameter of 5.1-10.2 cm on each plot were randomly selected to be burned for either 30
or 40 seconds.
Chinese privet stems were divided in the two diameter classes (1.27-5.0 cm and
5.1-10.2 cm diameter at the base) based on the observation of what size plants were
available in the area. The fire was powered using a torch (Red Dragon, model: VT 3-30 C
500,000 BTU/HR) and a 7.0 kg propane tank. The burn time was taken using a
stopwatch. In 2010 treatments were applied in winter (February and March) of 2010,
25
Table 2.3. Treatment design for each season, year, diameter class, and burn time of
privet.
Season, number of
Replications
Diameter at Base of
plots
Burn Time (s)
Stem Class (cm)
Control, 4 plots
n=5 plants per plot
Size Class 1: 1.27-5.0
None
from each of the two
Size class 2: 5.1-10.2
None
size classes
Burn in Winter, Spring,
n=5 plants per plot
Size Class 1: 1.27-5.0
10; 20
and Summer of 2010, 5
for each of the four
Size class 2: 5.1-10.2
30; 40
plots each season
burn times
Burn in Winter, Spring,
n=5 plants per plot
Size Class 1: 1.27-5.0
10; 20
and Summer of 2011, 7
for each of the four
Size class 2: 5.1-10.2
30; 40
plots each season
burn times
spring (April and May) 2010, and summer (August) 2010. In 2011 treatments were
applied in winter (January and February) and spring (April and May), (Table 2.4).
Table 2.4. Dates of treatments and when data was collected from 2010 to 2011 for privet.
Parameter checked
Season and Date of Treatment Application
and time since
Control
Winter
Spring
Summer
Winter
Spring
treatment
N/A
Feb/Mar,
Apr/May,
Aug, 2010
Jan/Feb,
Apr, 2011
2010
2010
Jul, 2010
Jul, 2010
Jul, 2010
May, 2011
Aug, 2011
Aug, 2011
Aug,
2011
Aug, 2011
Aug, 2011
Aug, 2011
N/A
N/A
Aug,
2010
Jul, 2010
Jul, 2010
May, 2011
Aug, 2011
Aug, 2011
2011
Mortality
After 1 growing
season
After 2 growing
seasons
Sprouts
After 1 growing
season
Note: N/A= mortality was not included in this analysis after the second growing season
for the winter and spring of 2011 burn because the mortality was only examined once.
26
Sprouts were considered stump sprouts if they were 1.0 cm or less from the main
stem. Any stem beyond that distance was considered root sprouts and data for it was not
collected. Stump sprouts that grew after the winter 2010 and spring 2010 burn were
recorded in July, 2010. Those burned in summer, 2010 were recorded in May, 2011, and
those burned in winter and spring of 2011 were recorded in August, 2011 (Table 2.4).
Stump sprouts that grew after the winter 2010 burn and spring 2010 burn were burned in
July of 2010 and analyzed separately from the other sprouting data. A 2 mm thick metal
sheet was placed between the main stem and the sprout during burning to prevent the
main stem from being re-burned. A comparison was made between the mortality rate of
burned sprouts to unburned sprouts.
Two hundred fifty-eight royal paulownia trees were treated, and an additional 23
served as the control. Before treatment the 258 trees and the controls were divided into
two diameter at breast height (dbh) classes: dbh ≤ 20.1 cm and dbh ≥ 20.2 cm. Ten trees
from the dbh ≤ 20.1 cm size class and 13 trees from the dbh ≥ 20.2 cm size class were
randomly selected as control treatment and were left unburned (Table 2.5). In both
diameter classes the trees were randomly selected to be burned during winter, spring, or
summer. In the dbh ≤ 20.1 cm size class, 61 trees were randomly selected to be burned
for 15 seconds, while 56 trees were selected to be burned for 30 seconds. In the dbh≥
20.2 cm size class, 69 trees were randomly selected to be burned for 40 seconds, while 72
trees were selected to be burned for 60 seconds. All trees were flagged with numbers for
identification. The fire was powered using a torch (Red Dragon, model: VT 3-30 C
500,000 BTU/HR) and a 7 kg propane tank. The burn time was recorded using a
27
Table 2.5. Paulownia treatment design.
Paulownia
Season of Burn
replications
Diameter Class
Burn Time (s)
(cm)
Control n=10
None
DBH ≤ 20.1
None
Control n=13
None
DBH ≥ 20.2
None
n=21
Winter 2010
DBH ≤ 20.1
15
n=22
““
DBH ≤ 20.1
30
n=23
““
DBH ≥ 20.2
40
n=25
““
DBH ≥ 20.2
60
n=21
Spring 2010
DBH ≤ 20.1
15
n=17
““
DBH ≤ 20.1
30
n=23
““
DBH ≥ 20.2
40
n=23
““
DBH ≥ 20.2
60
n=19
Summer 2010
DBH ≤ 20.1
15
n=17
““
DBH ≤ 20.1
30
n=23
““
DBH ≥ 20.2
40
n=24
““
DBH ≥ 20.2
60
stopwatch. Treatments were applied in winter (February and March) of 2010, spring
(April and May) 2010, and summer (August) 2010. Mortality was examined and
documented in summer of 2011.
Sprouts were considered stump sprouts if they were at a distance of 0.64 cm or
less from the main stem. Any stem beyond that distance was considered a root sprout and
data for it was not collected. All stump sprouts from the winter, spring, and summer 2010
burn were recorded in August of 2010, and examined again one year later. When they
were recorded in August of 2010 many of the stump sprouts did not have leaves and
looked as if they were dying. By August 2011 many of the stump sprouts that originally
28
did not have any leaves grew leaves, and there was presence of more stump sprouts in
trees that originally did not have any. All stump sprouts observed in August 2011, with or
without leaves were included in the analysis.
Hypothesis and Statistical Analysis
Tested was whether burning for various lengths of time during different seasons
caused different mortality in two diameter size classes of paulownia trees. Also tested
was if the various burn lengths and season had an effect on stump sprouts. Chi-square
was used to test if there was a difference in mortality and sprouting among the seasons of
treatments for each burn length, and also used to test the differences in mortality and
sprouting among each treatment including the control regardless of season. Bonferoni
adjustment was used for multiple comparisons. Chi-square was used to test the difference
in mortality and sprouting among the two treatment applications (burn times) in each
season for each diameter class. Chi-square was used in most cases, but Fisher’s Exact
Test was used instead in instances when cells have a count of less than 5. Results were
considered to be significant if p < 0.1 for the statistical tests. This relatively liberal alpha
level was used because my method of invasive species control is new and there are no
results from such treatments currently found in literature.
The hypotheses tested was whether burning during different seasons caused
different mortality and different stump sprouting in honeysuckle, privet, and paulownia
after one growing season and also after two growing seasons except for paulownia. Also
tested if there is a difference in mortality and in sprouting after burning privet and
paulownia from two size classes, each class for two different lengths of time. The
29
mortality and sprouting were also compared to those of control plants that were not
burned. Tukey-Kramer adjustments for multiple comparisons was applied. The
experimental design for all species was a split plot design.
30
CHAPTER 3
RESULTS
Mortality and Sprouting of Honeysuckle after One Growing Season
Mortality in the control was significantly less than in the burned plants (all
seasons of treatment pooled, F(3,50)=186.0, all p<0.001, Figure 3.1). Plants that were not
burned did not die (Table 3.1). The greatest mortality occurred after the spring and
summer burn, 97.0% and 99.5%, respectively, while the winter burn resulted in an
average mortality of 85.9% (Table 3.1, Figure 3.1). There was no difference in mortality
after the spring and after the summer burn (p=0.840), but there was 11.1 % more
mortality after the spring burn than after the winter burn and 13.6% more mortality after
the summer burn than after the winter burn (p<0.001, Table 3.2).
Differences in sprouting average occurred between the control and the burned
plants (all seasons pooled, F(3,50)=32.59, p<0.001, Figure 3.2). The most sprouting
occurred after the winter burn with an average of 5.1 sprouts per plant (Table 3.3). Spring
and summer burn resulted in an average of 0.6 and 1.9 sprouts and had less sprouts than
the winter burn (all p<0.001, Table 3.4). No differences in sprouting occurred in the
control and spring burn or a summer burn (p=0.926, p=0.190, respectively). Differences
in sprouting were also not found between plants burned in the spring and summer
(p=0.129, Table 3.4, Figure 3.2).
31
One Growing Season
Two Growing Seasons
B
100
B
B
BC
C
C
90
Percent Mortality
80
70
60
50
40
30
20
10
A
A
0
Control
Spring
Summer
Winter
Season of Treatment
Figure 3.1. Percent mean mortality and standard error of honeysuckle after
one and two growing seasons. White bars, represent mortality after one
growing season, and the same letters indicate no difference among the white
bars at the p<0.1 level. Similarly for the shaded bars.
Table 3.1: Percent mean mortality and standard error in the control and 5 s
burn for honeysuckle.
Burn
Length (s)
Winter
After one growing season
0
0.0±0.0
5
85.9±2.6
After two growing seasons
0
0.0±0.0
5
98.0±0.8
Season of Burn
Spring
Summer
0.0±0.0
97.0±1.1
0.0±0.0
99.5±0.5
0.0
94.1
0.0±0.0
100.0±0.0
0.0±0.0
99.5±0.5
0.0
99.2
32
Average
Mortality
Table 3.2. Difference in plant mortality after burning in different seasons
for honeysuckle.
Treatment
Versus Treatment
Control
Control
Control
Spring
Spring
Summer
Spring
Summer
Winter
Summer
Winter
Winter
Difference in Mean
Mortality %
-97.0
-99.5
-85.9
-2.5
11.1
13.6
n, n
4, 20
4, 10
4, 20
20, 10
20, 20
10, 20
P-value
<0.001
<0.001
<0.001
0.840
<0.001
<0.001
Note: The mortality data was collected the following growing season after
treatment was applied. A one-way ANOVA was used for analysis with
Tukey-Kramer adjustment for multiple comparisons.
B
Average Number of Sprouts Per Plant
6
One Growing Season
5
Two Growing Seasons
4
3
A
B
2
A
A
1
C
A
N/A
0
Control
Spring
Summer
Winter
Season of Treatment
Figure 3.2. Average number of sprouts per honeysuckle bush and standard error
after one and two growing seasons. White bars, represent sprouts after one
growing season, and the same letters indicate no difference among the white bars
at the p<0.1 level. Similarly for the shaded bars.
33
Table 3.3. Standard error and average number of sprouts per plant in the
control and 5 s burn for each season in honeysuckle.
Burn
Length (s)
Winter
After one growing season
0
0.0±0.0
5
5.1±0.5
After two growing seasons
5
0.2±0.1
Sprouting
Spring
Summer
Average
Sprouting
0.0±0.0
0.6±0.1
0.0±0.0
1.9±0.3
0.0
2.5
0.9±0.1
1.6±0.3
0.9
Note: Sprouting was examined after the first and second growing season from
the time treatment was applied.
Table 3.4. Difference in the number of sprouts per plant one growing season after
burning in the winter, spring or summer and no burning for honeysuckle.
comparisons.
Treatment
Control
Control
Control
Spring
Spring
Summer
Versus Treatment
Spring
Summer
Winter
Summer
Winter
Winter
Difference in Number
of Sprouts/Plant
-0.6
-1.9
-5.1
-1.3
-4.5
-3.2
n, n
4, 20
4, 10
4, 20
20, 10
20, 20
10, 20
P-value
0.926
0.190
<0.001
0.129
<0.001
<0.001
Note: Used was a one-way ANOVA analysis with Tukey-Kramer adjustment for
multiple
Mortality and Sprouting of Honeysuckle after Two Growing Seasons
After two growing seasons, the mortality in the control plants was significantly
less than in the burned plants (all seasons of treatment pooled) (F(3,40)=5694.1, p<0.001).
There were no differences between mortality in spring and summer (p=0.810) or between
summer and winter (p=0.103, Table 3.5). The average spring burn resulted in complete
mortality of 100%, while mortality after summer treatment was 99.5%, and after winter
treatment was 98% (Table 3.1).
34
Table 3.5. Difference in honeysuckle mortality after burning during
different seasons.
Treatment
Control
Control
Control
Spring
Spring
Summer
Versus Treatment
Spring
Summer
Winter
Summer
Winter
Winter
Mean Mortality %
-100.0
-99.5
-98.0
0.5
2.0
1.5
n, n P-value
4, 20
<0.001
4, 10
<0.001
4, 10
<0.001
20, 10
0.810
20, 20
0.005
10, 10
0.103
Note: The mortality data was collected during the second growing season
after treatment was applied. Used was a one-way ANOVA analysis with
Tukey-Kramer adjustment for multiple comparisons.
Differences in sprouting occurred among all seasons after burning (F(2,27)= 10.80,
p<0.001) and sprouting occurred after burning in the winter, spring, and summer seasons:
0.2, 0.9, and 1.6 sprouts per plant, respectively (Table 3.3). Both spring and summer
burns resulted in greater sprouting than winter burns (p=0.069, p<0.001, respectively;
Table 3.6). The summer burn caused more sprouts than the spring burn (p=0.067, Table
3.6).
Table 3.6. The difference in the number of honeysuckle sprouts per plant two
growing seasons after treatment.
Treatment Versus Treatment
Spring
Spring
Summer
Summer
Winter
Winter
Difference in Number
of Sprouts/Plant
-0.7
0.6
1.4
n, n
10, 10
10, 10
10, 10
P-value
0.067
0.069
<0.001
Note: Used was a one-way ANOVA analysis with Tukey-Kramer adjustment for
multiple comparisons.
35
Of the plants that were burned in the winter of 2010, some plants sprouted and
others did not. The plants that sprouted were burned in spring of 2010. By August, 2011
plants that originally did not have sprouts after the winter treatment of 2010 still had 0.0
sprouts per plant. As for the plants that sprouted after the winter 2010 burn and whose
sprouts were burned in spring of 2010, by August, 2011 sprouting average per plant was
2.0.
The number of stump sprouts that grew after the main stems were burned in
winter 2010, whose sprouts were burned in spring 2010, were compared to the number of
sprouts that grew after the main stems were burned in winter 2011 whose sprouts were
not burned. There were no differences in sprouting between the two groups (F(1,16)= 0.01,
p=0.917, Figure 3.3). The average number of sprouts for plants burned in winter 2010
and in winter 2011 was 1.7% in both cases.
Sprouting Average Per Plant
2.5
A
2
A
1.5
1
0.5
0
Sprouts Burned in Winter 2010
Sprouts Not Burned in Winter 2011
Treatment
Figure 3.3. Average number of honeysuckle sprouts per plant and standard error in
August 2011 one growing season after treatment. The same letters indicate no difference
at the p<0.1 level.
36
Mortality and Sprouting of Chinese Privet after One Growing Season
The predictor variables season, treatment, and the interaction produced a
significant overall model for the mortality in the small diameter size class when the
control was included in the dataset (F(1,60)=145.45, p<0.001, Figure 3.4). After removing
the control from the dataset, there was no significant overall model (F(5,52)=1.11,
p=0.367). The average mortality in the control was 0.0% while the overall mortality for
all other treatments was 91.4%.
One Growing Season
Two Growing Seasons
Percent Mortality
B
100
90
80
70
60
50
40
30
20
10
0
B
B
B
A
Control
B
B
A
Spring
Summer
Winter
Season of Treatment
Figure 3.4. Percent mean mortality and standard error in Chinese privet after one and
two growing seasons in the small diameter size class. White bars, represent mortality
after one growing season, and the same letters indicate no difference among the white
bars at the p<0.1 level. Similarly for the shaded bars.
The overall model for predicting stem mortality in the large diameter size class,
when the data for the control plants was included in the dataset, was significant
(treatments were no burn, winter burn, spring burn, and summer burn), (F(3,58)=6.27,
p<0.001). The model remained significant when the control was removed from the
dataset (F(5,52)=2.45, p=0.046), because of differences in mortality among the seasons of
37
burning. Following the examination of the pair comparisons by applying the TukeyKramer adjustment, there were differences between: spring versus summer, summer
versus winter, and summer versus no burn, (p=0.040, 0.005, and 0.002, respectively;
Table 3.7, Figure 3.5). The summer burn resulted in the greatest average mortality of
59.0%, while mortality in the other seasons was: spring 32.5%, winter 25.2% (Table 3.8),
mortality in the control 0.0%.
Table 3.7. The differences in the average percent mortality after 30 s and 40 s
burn treatments (combined) after one and two growing seasons for privet.
Treatment
Versus
Treatment
Difference in
Percent Mortality
First Growing Season
Large Diameter
Control
Winter
Control
Spring
Control
Summer
Winter
Spring
Winter
Summer
Spring
Summer
Second Growing Season
Large Diameter
Control
Winter
Control
Spring
Control
Summer
Winter
Spring
Winter
Summer
Spring
Summer
P-value
-25.2
-32.5
-59.0
-7.3
-33.8
-26.5
0.297
0.102
0.002
0.761
0.005
0.040
-42.5
-80.7
-67.0
-38.2
-24.5
13.7
0.002
<0.001
<0.001
<0.001
0.026
0.352
Note: Used was Tukey-Kramer adjustment for multiple comparisons.
The overall model was significant for the number of sprouts per plant in the small
diameter size class, where the independent variables were season, treatment, and their
interaction. The number of sprouts per plant in the control was significantly less than the
number of sprouts per plant in the treatments (F(2,59)=5.17, p=0.009, Figure 3.6). When the
38
control was removed there was no significant overall model (F(5,52)=1.63, p=0.168). The
overall model for the number of sprouts per plant in the large diameter size class, where
the predictors were: season, treatment, and their interaction, were significant when the
control was included in the dataset. The number of sprouts per plant was significantly
greater after the winter burn than after the spring burn, summer burn, and after not
burning (all p<0.001 Table 3.9, Figure 3.7). The greatest number of sprouts per plant
occurred after winter burn (1.6 sprouts per plant), followed by spring burn (0.8 sprouts
per plant) and summer burn (0.6 sprouts per plant; Table 3.10). There were 0.0 sprouts
per plant in the control treatment. When the control was removed from the dataset the
overall model for the number of sprouts per plant in the large diameter size class
remained significant (F(5,52)=5.77, p<0.001).
Percent Mortality
One Growing Season
Two Growing Seasons
100
90
80
70
60
50
40
30
20
10
0
B
B
B
C
A
A
A
A
Control
Spring
Summer
Winter
Season of Treatment
Figure 3.5. Percent mean mortality and standard error in Chinese privet after
one and two growing seasons in the large diameter size class. White bars,
represent mortality after one growing season, and the same letters indicate no
difference among the white bars at the p<0.1 level. Similarly for the shaded
bars.
39
Table 3.8. Percent mean mortality and standard error in the small and large
diameter classes of Chinese privet after one and two growing seasons.
Season of Burn
Spring
Summer
91.6±5.2
93.3±2.8
92.0±8.0
100.0±0.0
92.5
96.0
28.3±8.0
36.7±7.7
62.0±4.9
56.0±14.7
32.5
59.0
96.0±4.0
100.0±0.0
96.0±4.0
100.0±0.0
98.0
98.0
80.0±8.9
81.3±8.3
66.0±6.0
68.0±12.0
80.7
67.0
Average
Mortality
89.0
95.5
39.5
38.3
96.0
95.3
65.0
61.8
2.5
B
2
B
Plant
Average Number of Sprouts Per
Burn
Length (s)
Winter
After one growing season
Small Diameter Class
10
83.3±5.4
20
93.3±3.8
Average Mortality
88.3
Large Diameter Class
30
28.3±8.3
40
22.1±7.6
Average Mortality
25.2
After two growing seasons
Small Diameter Class
10
96.0±4.0
20
86.0±9.8
Average Mortality
91.0
Large Diameter Class
30
49.0±9.5
40
36.0±7.5
Average Mortality
42.5
1.5
1
0.5
A
0
Control
10
20
Burn Times (s)
Figure 3.6. Average number of sprouts and standard error of Chinese privet after one and
two growing seasons in the small diameter size class. The same letters indicate no
difference at the p<0.1 level.
40
Table 3.9. The differences in number of sprouts per plant for the 30 s and 40 s
treatments (combined) after treatment (control, winter, spring, and summer
burn) for privet.
Treatment
Versus
Treatment
Large Diameter
Control
Control
Control
Winter
Winter
Spring
Difference in
Sprouts Per Tree
Winter
Spring
Summer
Spring
Summer
Summer
-1.6
-0.8
-0.6
0.8
1.0
0.2
P-value
<0.001
0.124
0.361
<0.001
<0.001
0.922
Plant
Average Number of Sprouts Per
Note: Used was Tukey-Kramer adjustment for multiple comparisons.
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
B
A
A
A
Control
spring
summer
winter
Se ason of Treatme nt
Figure 3.7. Average number of Chinese privet sprouts per plant and standard error
after one and two growing seasons in the large diameter size class. The same letters
indicate no difference at the p<0.1 level.
After the 2010 winter and spring burn, sprouting occurred in some plants and did
not in others. For the plants on which sprouting did occur, the sprouts were burned in
August, 2010. The sprouts were burned for either 5 s or 10 s. The sprouts on each
treatment plant were burned for the same length of time and the choice between 5 s and
10 s was made randomly. The number of live sprouts in May 2011 was not different
among the plants burned for 5 s or 10 s. This was true for both size classes (Table 3.11).
41
Table 3.10. Average number of Chinese privet sprouts per plant and standard error
in the small and large diameter classes after one growing season.
Burn
Length (s)
Winter
After one growing season
Small Diameter Class
10
1.8±0.3
20
1.9±0.5
Average Sprouting Per Plant
1.9
Large Diameter Class
30
1.6±0.2
40
1.6±0.3
Average Sprouting Per Plant
1.6
Season of Burn
Spring
Summer
Average
Sprouting
Per Bush
1.5±0.2
1.2±0.2
2.4±0.9
1.1±0.3
1.9
1.4
1.4
1.8
1.65
0.8±0.2
0.7±0.1
0.7±0.3
0.6±0.1
1.03
0.97
0.8
0.6
1.00
Since no differences occurred in the response to the 5 s and 10 s burning of
sprouts in plants of either size class and either season of burn of the original plant stem,
the data from the two sprout burn times were combined. This data was then used to
compare the number of stump sprouts (as of May 2011) of plants burned in winter 2010
with the number of stump sprouts (as of August 2011) of plants burned in winter 2011.
This data was also used to compare the number of stump sprouts (as of May 2011) of the
plants burned in spring 2010 with the number of stump sprouts (as of August 2011) of
plants burned in spring 2011. The only observed difference was that on average there was
one more sprout per bush in the small diameter class for plants whose stems were
originally burned in winter 2010 (and whose sprouts were later burned) than in the plants
burned in winter 2011 (whose sprouts were not burned, F(1,14)=3.73, p=0.074, Table
3.12).
42
Table 3.11. Differences in sprouts per plant when burned for 5 s or 10 s for
privet.
Treatment
Versus
Treatment
Small Diameter
Original stem
burn in Winter
2010
Sprout burn
for 5 s
Original stem
burn in Spring
2010
Sprout burn
for 5 s
Large Diameter
Original stem
burn in Winter
2010
Sprout burn
for 5 s
Original stem
burn in Spring
2010
Sprout burn
for 5 s
Difference in
Sprouts Per Bush
F-value
P-value
Sprout burn
for 10 s
0.4
0.45
0.525
Sprout burn
for 10 s
-1.5
2.83
0.131
Sprout burn
for 10 s
-0.9
0.88
0.375
Sprout burn
for 10 s
-0.0
0.00
0.978
Note. The original stems were burned in either winter 2010 or spring 2010,
followed by burning of the sprouts in August 2010 for 5 s or 10 s.
Table 3.12. Difference in final number of privet stump sprouts between plants burned
in winter 2010 (whose sprouts were burned in August 2010) and plants burned in
winter 2011 (whose sprouts were not burned); analogous for spring.
Treatment (date of main
stem burn/date of sprout
burn)
Small Diameter
Winter 2010/Aug 2010
Spring 2010/Aug 2010
Large Diameter
Winter 2010/Aug 2010
Spring 2010/Aug 2010
Versus Treatment (date
of main stem burn/date
of sprout burn)
Difference FP-value
in Sprouts value
Per Bush
Winter 2011/none
Spring 2011/none
1.0
-0.3
3.73
0.26
0.074
0.618
Winter 2011/none
Spring 2011/none
-0.2
1.0
0.08
2.35
0.778
0.146
43
Mortality and Sprouting of Chinese Privet after Two Growing Seasons
When the data for the control was included in the dataset, there was a significant
overall model for predicting stem mortality in the small diameter size from the predictor
variables season, treatment, and their interaction (F(1,32)=292.27, p<0.001). After the data
for the control plants was removed from the dataset, the model was no longer significant
(F(5,24)=1.09, p=0.389). The average mortality in the control plants was 0.0%, while
mortality in all other treatments was 95.7%.
Unlike the results with the small diameter size class, there was a significant
overall model for predicting stem mortality in the large diameter size class, when the
control plants were included in the analyzed dataset (F(3,30)=21.78, p<0.001) and when the
data for the control was removed from the dataset (F(5,24)=4.00, p=0.009). Following the
examination of the pair comparisons and applying the Tukey-Kramer adjustment,
differences in percent stem mortality were found between the following: stems burned in
spring versus those burned in winter, spring versus control, winter versus summer, winter
versus control, and summer versus control, (p<0.001, <0.001, 0.026, 0.002, <0.001,
respectively Table 3.7, Figure 3.5). Spring had the greatest average mortality of 80.7%,
while mortality in the other seasons was: summer 67.0% and winter 42.5% (Table 3.8).
Mortality in the control was 0.0%.
Paulownia Mortality
The mortality data collected in August of 2011, which was at least one full year
after burning was completed in winter, spring, and summer of 2010, indicated that not all
treatments were able to cause mortality in the experimental trees (Table 3.13). There was
44
no tree mortality among the trees from the control treatment, or among the trees from the
small diameter class that were burned for 15 s, regardless of the season of burn (Table
3.13). Mortality did occur, however, as a result of the longer burn of 30 s in the small
diameter class, as well as 40 s and 60 s in the larger diameter class. Greater mortality
occurred in the small diameter trees after 30 s burn and in the large diameter trees after
60 s burn than in the control (p=0.035, p=0.005, respectively, Table 3.14). However, the
percent mortality after burning trees from the large diameters for 40 s was not different
from the percent dead in the control (p=0.333, Table 3.14). When the mortality data from
all seasons was combined, for the small diameter trees there was more mortality after
burning for 30 s than for 15 s, and for the large diameter trees there was more mortality
after burning for 60 s than 40 s (p<0.001 in both cases, Table 3.14, Figure 3.8 and 3.9).
The mortality after 30 s treatment was an average of 25% and after 60 s treatment was an
average of 31.9% (Table 3.13).
Table 3.13. Percent of tree mortality and standard error in August of
2011 for treatments applied in winter, spring, and summer of 2010 for
paulownia.
Burn length (s) Winter
Spring
Summer
Average
Small Diameter Class
0
0.0±0.0
0.0±0.0
0.0±0.0
0.0
15
0.0±0.0
0.0±0.0
0.0±0.0
0.0
30
13.6±7.5
17.7±9.5
47.1±12.5 25.0
Large Diameter Class
0
0.0±0.0
0.0±0.0
0.0±0.0
0.0
40
0.0±0.0
0.0±0.0
17.4±8.1
5.8
60
4.0±4.0
26.1±9.4
66.7±9.8
31.9
45
Table 3.14. Effect of burning paulownia for different lengths of time during all
seasons combined on percent mortality, compared to the control and among the
various burn lengths for small and large diameter classes.
Treatment
Versus
Difference in
Treatment Mortality (%)
Small Diameter Class
Control
*Control
15 s
Large Diameter Class
*Control
*Control
40 s
n, n
P-value
15 s
30 s
30 s
0.0
-25.0
-25.0
10, 61
10, 61
61, 56
N/A
0.035
<0.001
40 s
60 s
60 s
-5.8
-31.9
-26.1
13, 69
13, 72
69, 72
0.333
0.005
<0.001
* Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square
tests were used. Used was Bonferroni adjustment for multiple comparisons.
35
B
Percent Mortality
30
25
20
15
10
5
A
0
15 s
30 s
Burn Time (s)
Figure 3.8. Paulownia mean percent mortality and standard error in the small diameter
class after a 15 s and 30 s burn. The same letters indicate no difference at the p<0.1 level.
There was no difference in mortality between trees burned in the winter for 15 s
and those burned for 30 s (P=0.233, Table 3.15). However, when the burn was carried out
in the spring or summer, the 30 s burn resulted in greater mortality than the 15 s burn.
(p=0.081, p<0.001, respectively, Table 3.15). Similar results were observed for the large
46
diameter class, burning for 40 s or 60 s in the winter resulted in the same percent
mortality (p=1.000), but burning in the spring and summer resulted in greater mortality of
the trees burned for 60 s than those burned for 40 s. (p=0.022, p=0.001, respectively,
Table 3.15).
B
40
Percent Mortality
35
30
25
20
15
10
A
5
0
40 s
60s
Burn Time (s)
Figure 3.9. Paulownia mean percent mortality and standard error in the large diameter
class after a 40 s and 60 s burn. The same letters indicate no difference at the p<0.1
level.
Table 3.15. Effect of burning paulownia for different lengths of time during the seasons:
winter, spring, and summer on percent tree mortality in the small and large diameter
classes.
Season
Small Diameter Class
*Winter
*Spring
*Summer
Large Diameter Class
*Winter
*Spring
Summer
Treatment Versus
Treatment
Difference in
Mortality
(%)
n, n
P-value
15 s
15 s
15 s
30 s
30 s
30 s
-13.6
-17.7
-47.1
21, 22
21, 17
19, 17
0.233
0.081
<0.001
40 s
40 s
40 s
60 s
60 s
60 s
-4.0
-26.1
-49.3
23, 25
23, 23
23, 24
1.000
0.022
0.001
Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square tests was
used.
47
None of the trees died if they were burned for 15 s, regardless of the season of
burn, so the season effect was investigated further (Table 3.16). Similarly, no comparison
was made between the season effect on mortality of the trees burned for 40 s in the winter
and spring, because no mortality was observed (Table 3.16). There was no difference in
percent mortality after burning for 30 s in the winter versus the spring (p=0.333, Table
3.16). However, there was a difference in percent tree mortality in each season for each
of the other burn lengths (Table 3.16). For the 60 s burn lengths, mortality after spring
burn was greater than after winter burn. After the 40 s and 60 s burn lengths, mortality
after summer burn was greater than after spring burn, and mortality after summer burn
was greater than after winter burn (Table 3.16). It was similar with the 30 s burn, with the
exception that mortality after the winter burn was not different from mortality after the
spring burn.
Paulownia Sprouts
Stump sprouting data was collected in all seasons, but no sprouting occurred in
the control (Table 3.17). Stump sprouting observed in August, 2011, which was a
minimum of one full year after burning that took place in winter, spring, and summer of
2010, showed that sprouting occurred after each of the burn lengths of 15s, 30 s, 40 s, and
60 s. Sprouting after burning for 40 s and 60 s was more common than in the control trees
(p=0.067, p=0.011, respectively), but no difference was found between the percent of
trees with new sprouts in the control and the 15 s burn or the control and 30 s burn
(p=0.333, p=0.114, respectively, Table 3.18). The greatest percent of trees with stump
sprouts, 29.6%, occurred after the 60 s burn (Table 3.17).
48
Table 3.16. The effect of burning paulownia percent mortality when burning for different
seasons and burn lengths (s) of: 15, 30, 40, and 60 s.
Burn Time
Treatment
Small Diameter Class
15 s
Winter
15 s
Winter
15 s
Spring
*30 s
Winter
*30 s
Winter
30 s
Spring
Large Diameter Class
40 s
Winter
*40 s
Winter
*40 s
Spring
*60 s
Winter
60 s
Winter
60 s
Spring
Versus
Treatment
Difference
In Mortality
(%)
n, n
P-value
Spring
Summer
Summer
Spring
Summer
Summer
0.0
0.0
0.0
-4.1
-33.5
-29.4
21, 21
21, 19
21, 19
22, 17
22, 17
17, 17
N/A
N/A
N/A
0.333
0.011
0.022
Spring
Summer
Summer
Spring
Summer
Summer
0.0
-17.4
-17.4
-22.1
-62.7
-40.6
23, 23
23, 23
23, 23
25, 23
25, 24
23, 24
N/A
0.036
0.036
0.015
<0.001
0.005
* Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square tests was
used. Used was Bonferroni adjustment for multiple comparisons.
Table 3.17. Mean percent and standard error of paulownia trees with
stump sprouts in each treatment
Burn length (s) Winter
Spring
Summer
Average
Small diameter class
0
0.0±0.0
0.0±0.0
0.0±0.0
0.0
15
14.3±7.8
0.0±0.0
5.3±5.3
6.6
30
9.1±6.3
17.7±9.5
17.7±9.5 14.3
Large diameter class
0
0.0±0.0
0.0±0.0
0.0±0.0
0.0
40
4.6±4.5
13.0±7.2
27.3±9.7 14.9
60
30.4±9.8
30.4±9.8
28.0±9.2 29.6
There was no difference in percent of trees with sprouts after burning for 15 s and
for 30 s during the winter or summer (p=0.664, p=0.324, respectively, Table 3.19).
49
Table 3.18. Effect of burning on the percent of paulownia trees with new stump sprouts
when the main stem was burned for different lengths of time during all seasons combined
compared to the control and other burn lengths.
Treatment
Versus
Treatment
Small Diameter Class
*Control
*Control
15 s
Large Diameter Class
*Control
*Control
40 s
Difference in
Percent of Trees
with New Sprouts
n, n
P-value
15 s
30 s
30 s
-6.6
-14.3
-7.7
10, 61
10, 56
61, 56
0.333
0.114
0.056
40 s
60 s
60 s
-14.9
-29.6
-14.7
13, 67
13, 71
67, 71
0.067
0.011
0.013
* Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square tests was
used. Used was Bonferroni adjustment for multiple comparisons.
However, greater mortality occurred after the spring 30s burn than the spring 15 s burn
(p=0.081, Table 3.19). There was no difference in percent of trees with stump sprouts
after burning for 40 s or 60 s during the spring (p=0.153, Table 3.19). The same was
observed after burning during summer as well (p=0.956, Table 3.19). Differences in
percent trees with sprouts were found in the 40 s treatment and 60 s treatment during
winter (p=0.047, Table 3.19).
No differences were found in sprouting occurrence when the main stem was
burned for 30 s between the following: winter and spring, winter and summer, and spring
and summer (p=0.212, p=0.212, p=0.333, respectively; Table 3.20, Figure 3.10). Similar
lack of differences between seasons was found in the results for 60 s burns (Table 3.20,
Figure 3.11). The same sprouting average of 30.4% was found after the winter and spring
50
Table 3.19. Effect of burn length in different seasons on the percent of paulownia trees
with stump sprouts.
Season
Treatment
Versus
Treatment
Small Diameter Class
*Winter
15 s
*Spring
15 s
*Summer
15 s
Large Diameter Class
*Winter
40 s
Spring
40 s
Summer
40 s
Difference in Tree
Percentage with New
Sprouts
n, n
Pvalue
30 s
30 s
30 s
5.2
-17.7
-12.4
21, 22
21, 17
19, 17
0.664
0.081
0.324
60 s
60 s
60 s
-25.8
-17.4
-0.7
22,23
23,23
22, 25
0.047
0.153
0.956
* Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square tests was
used.
60 s burn. The 60 s summer burn caused on average, 28% of trees to sprout (Table 3.17).
Similarly, seasonal differences were not found in comparisons of sprouting after winter
and summer burn for 15 s, spring and summer burn for 15 s, and winter and spring burn
for 40 s (p=0.202, p=0.158, p=0.203, respectively; Table 3.20). Seasonal differences were
found in comparisons of sprouting after spring and winter burn for 15 s, and winter and
summer burn for 40 s, and spring and summer burn for 40 s (p=0.077, 0.032, and
p=0.095 Table 3.20). No sprouting occurred after burning for 15 s in the spring, but
14.3% average sprouting did occur after the 15 s winter burn (Table 3.17). Sprouting
occurred almost 6 times more often after the summer 40 s burn, an average of 27.3%,
than after the winter 40 s burn, and occurred at almost double the rate of sprouting after
the spring 40 s burn (Table 3.17).
51
Table 3.20. The effect of burning on stump sprouts when the main paulownia stem is
burned, during different seasons and burn lengths (s) 15 s, 30 s, 40 s, and 60 s.
Burn Time
Treatment
Small Diameter Class
*15 s
Winter
*15 s
Winter
*15 s
Spring
*30 s
Winter
*30 s
Winter
*30 s
Spring
Large Diameter Class
*40 s
Winter
*40 s
Winter
*40 s
Spring
60 s
Winter
60 s
Winter
60 s
Spring
Versus
Treatment
Difference in
Tree Percentage
with New Sprouts
n, n
P-value
Spring
Summer
Summer
Spring
Summer
Summer
14.3
9.0
-5.3
-8.6
-8.6
0.0
21, 21
21, 19
21, 19
22, 17
22, 17
17, 17
0.077
0.202
0.158
0.212
0.212
0.333
Spring
Summer
Summer
Spring
Summer
Summer
-8.4
-22.7
-14.3
0.0
2.4
2.4
22, 23
22, 22
23, 22
23, 23
23, 25
23, 25
0.203
0.032
0.095
0.333
0.284
0.284
Percent of Trees with Sprouts
* Indicates Fisher’s Exact Test analysis. In all other comparisons Chi-square tests was
used and Bonferroni adjustment for multiple comparisons.
30
A
A
25
20
A
15
10
5
0
W inter
S pring
S um m er
S e a son of Tre a tm e nt
Figure 3.10. Mean percent and standard error of small diameter paulownia trees
with sprouts after burning for 30 s in winter, spring, and summer. The same letters
indicate no difference at the p<0.1 level.
52
Percent of Trees with Sprouts
45
40
A
A
A
35
30
25
20
15
10
5
0
Winter
Spring
Summer
Season of Treatment
Figure 3.11. Mean percent and standard error of large diameter paulownia trees
with sprouts after burning for 60 s in winter, spring, and summer. The same letters
indicate no difference at the p<0.1 level.
53
CHAPTER 4
DISCUSSION
Results from my work demonstrate that applying fire to the base of the stem does
cause mortality in royal paulownia, honeysuckle, and Chinese privet. This study shows
that burning paulownia trees with diameters from 3.8 cm to 20.1 cm for 30 seconds and
burning trees with diameters from 20.2 cm to 68.6 cm for 60 seconds will result in greater
mortality than after a shorter fire exposure. Burning paulownia stems with diameters of
20.1 cm and below for 15 seconds should not be used because this time length of burning
was not effective. In a similar study stems of Acacia species were burned and the high
severity burn caused greater stem mortality than the low severity burn (Wright and
Clarke 2007). The most adequate season to burn in order to cause the greatest mortality in
paulownia is summer, which could be because there are less carbohydrate reserves in the
roots during summer than spring (Bowen and Pate 1993). Successful mortality can be
obtained by burning in spring as well, but burning in winter for the examined lengths of
time results in low levels of mortality. Similarly to my results, greater morality occurred
in Pinus ponderosa when burning took place in the growing seasons rather than in the
dormant seasons (Harrington 1993).
In the large diameter size class 5.1-10.2 cm of Chinese privet the average
mortality after two growing seasons was 80.7% for the spring burn and 67.0% for the
54
summer burn. In honeysuckle the average morality one growing season after spring burn
was 97.0% and after a summer burn was 99.5%. Burning honeysuckle and large diameter
Chinese privet in spring or summer was most effective as it caused the greatest mortality.
In a study of Lonicera morrowii after they were cut the greatest mortality occurred in the
spring (May) which was when total non-structural carbohydrates (TNC) levels were at
their lowest (Love and Anderson 2009). Burning small diameters of Chinese privet for 10
s or 20 s during any season resulted in similar mortality. This could have been due to the
fact that the study site floods occasionally and the stress from burning combined with
short term flooding increased the chance of death, especially in the smaller diameters,
although a study of waterlogging illustrates Chinese privet is tolerant of short term
flooding (Brown and Pezeshki 2000), the study did not include burning followed by
flooding.
Spring and summer burning may have had an effect because the plants were
actively growing, which is when they are most sensitive to burning. It may also be in part
because of the initial amount of fuel load around the base of the stem before burning and
the amount of moisture content in it. In this study, fuel around the base of the stem was
not removed for any of the species. After the application of fire by the torch, in some
instances, fire still burned past the targeted burn length because of the fuel load at or near
the base of the stem. In winter the leaf litter visually seemed moister than in spring or
summer. The dry fuel in the drier seasons could have caused the fire to linger longer, thus
increasing the chance of death.
Honeysuckle mortality after winter burn went from 86.0% after the first growing
season to 98.0% after the second growing season. This may be because TNC levels are
55
the highest in autumn (Love and Anderson 2009). When a burn is conducted during a
dormant season (winter) TNC levels are still high, and it may be possible TNC levels are
not exhausted at the beginning of the growing season which can cause continued growth
in the plant if the cambial layer was not completely damaged by the fire. It is possible
with time that TNC levels were decreased and winter mortality increased the following
growing season. The increase in mortality after a winter burn from one growing season to
the next could have been caused by exhausted TNC levels.
Sprouting occurred in all species after burning. In paulownia the least amount of
sprouting as well as the least amount of mortality occurred after the shorter 15 s burn for
the small diameter class, and in the shorter 40 s burn for the larger diameter class, which
was likely because the main stem was still alive, so the basal buds were not stimulated.
Mortality did not occur in the control of any of the three species and sprouting did not
occur in the control for paulownia or honeysuckle and was low for Chinese privet,
indicating that the burning is indeed the cause of the observed mortality and sprouting,
regardless of whether the burn managed to kill the above ground portion of the tree. Tree
and shrub species commonly re-sprout after a catastrophe by using stored carbohydrates
(Trlica and Cook 1971). In my study minimal sprouting occurred in the short length
burns likely because the trees were not severely damaged - they had low mortality levels
and as a result had lower sprouting rates.
Paulownia trees burned in the summer for 40 s sprouted more frequently than
trees burned in the winter or spring. However, this difference among seasons was not
observed for the 30 second treatment of smaller trees or 60 second treatment of larger
trees during any season. Such difference was not observed for the smaller diameter class
56
of Chinese privet either. In paulownia trees burned for 30 s or for 60 s and Chinese privet
burned for 10 s or 20 s no differences in sprouting occurred after burning in the three
seasons. This could be a result of the extremely hot fire that was applied. Other studies
have used prescribed burning which does not normally get as hot and burn as long as the
fire from the propane powered torch in this study. Due to the intense fire the basal buds
may have been damaged, as was desired, which resulted in similar sprouting for both
treatments for all seasons. Since sprouting occurs at similar rates regardless of season,
burning should be applied in frequent intervals (years) during each of the seasons to
determine how many intervals and in which season fire should be applied to successfully
eradicate these species. It took five annual burnings to finally reduce the stem numbers of
shrub live oak to what they were before the first treatment whereas, desert ceanothus
sprouts were almost all killed by a second burn (Pond and Cable 1961).
TNC levels are at their greatest in autumn (Love and Anderson 2009), and this
may be the reason why after the first growing season more sprouting occurred in
honeysuckle and Chinese privet (large diameter size class) after the winter burn than the
spring or summer burn. In honeysuckle sprouting after the second growing season
decreased after the winter and summer burn but increased slightly after the spring burn.
The decrease in sprouting may be due to a decrease in TNC, although the TNC levels
were not tested in this study. Competition among sprouts may be another reason for the
drop in number of sprouts after the second growing season, but further testing would be
needed to determine such a factor.
Sprouts in honeysuckle that appeared after the winter burn of 2010, were burned
in the spring of 2010. None of the sprouts were burned during the other seasons because
57
after checking the number of sprouts again in July of 2010 many of them were dying on
their own. A similar study found that the sprouts of Lonicera Xbella after a fire were not
very vigorous (Kline and McClintock 1994). Another study illustrated that within the first
year of growth new stems of forest grown shrubs tend to die (Luken 1988).
Sprouts from honeysuckle plants that were burned resulted in an average of two
new sprouts per plant the following growing season. It may be possible to eradicate this
invasive species with continued burning of the sprouts in a particular area. Lonicera
maackii that grew under a forest canopy sprouted but with repeated clipping, the number
of sprouts was reduced (Luken and Mattimiro 1991). In 1987 the total number of sprouts
was approximately 150 and with repeated clipping by 1988 the number of sprouts
dropped to approximately 75, by the following year sprout number dropped to
approximately 50 (Luken and Mattimiro 1991). In my study burning the main stem in
winter or summer reduced the number of sprouts from one growing season to the next
without an additional burn. In the repeated clipping study, treatments were applied
annually for three years. It is possible burning is more effective than clipping in terms of
effectively reducing the number of sprouts by applying one application. With repeated
burning each year the number of sprouts may reduce even more than by repeated
clipping. In this study honeysuckle plants without sprouts did not sprout again after a
growing season.
For the small diameter class Chinese privet, stump sprouts that emerged after the
winter 2010 burn were burned in August 2010. Following the burn the number of sprouts
per plant by May 2011 was significantly greater than the sprouts in August 2011, that
emerged after the winter 2011 burn (but the sprouts were not burned). This means that the
58
burning of the sprouts actually caused more sprouts than not burning them. Similar
results in Lonicera maackii were found with repeated clipping in an open area, the
number of sprouts continue to increase with repeated clipping (Luken and Mattimiro
1991). Results indicate carbohydrate reserves may have continued to be stored and
accumulated between clippings (Luken and Mattimiro 1991). This was not the case with
the spring burn. The small and large diameter class of privet burned in spring of 2010,
whose sprouts were also burned in August 2010, had fewer sprouts per tree in May 2011
than the un-burned sprouts that emerged in August 2011 from stems burned in spring
2011. Dormant season treatments have little effect on carbohydrate reserves in Lonicera
morrowii honeysuckle (Richburg and Patterson 2004). It is possible that since TNC levels
are at their lowest in spring (Love and Anderson 2009), and burning sprouts that arose
after a spring burn (which may have been produced by limited carbohydrate reserves)
further enhances the depletion of these reserves and results in lower rates of sprouting
over time. TNC levels are at their highest during a dormant season (Love and Anderson
2009) and by burning sprouts that arose after a winter burn (which may have been
produced by high carbohydrate reserves) will take longer to deplete these reserves and
sprouting will continue at high rates until the reserves are exhausted. Further research
should test if reburning the sprouts will cause less re-sprouting over time, or if by not
burning the sprouts they may die on their own over time. Preliminary results by Richburg
and Patterson (2003) show that to effectively reduce the amount of TNC, repeated
treatments of cutting or burning need to be applied during the growing season. It should
be kept into consideration that only stump sprouting data were collected and analyzed.
59
These species also sprout from the roots, so additional experimentation would be needed
to determine if this method is adequate at reducing root sprouting.
Conclusion
The novel method used in this study was successful at causing mortality in all
three species. Effective extermination of royal paulownia trees, bush honeysuckle, and
Chinese privet and controlling their sprouting is crucial for successful management of
these species. To successfully kill paulownia burning should take place in summer, and to
successfully kill honeysuckle and Chinese privet the burning should take place either in
the summer or spring. For greatest mortality of paulownia, trees between 3.8 cm and 20.1
cm in dbh should be burned for 30 seconds and trees between 20.2 cm and 68.6 cm for 60
seconds. This causes the most tree mortality, although stump sprouting may be
stimulated. Although the paulownia sprouts were not burned, burning the sprouts after the
following growing season may reduce the success rate of this species. Repeated burning
of the sprouts should be further studied for this species. In Garrya wrightii (Wright’s
silktassel) and Rhamnus crocea (hollyleaf buckthorn) these species were burned using a
torch by heat that reached 1,500° C. The sprouts from both species were completely
eliminated by four annual burns (Pond and Cable 1961). Honeysuckle should be burned
in the spring to cause the greatest mortality but the least amount of stump sprouting. The
results of this study suggest that Chinese privet stems with diameter between 1.27 cm and
5.0 cm can be burned in any season (winter, spring, or summer) and should be burned for
10 s to reduce the amount of time in the field. Diameters 5.1 to 10.2 cm should be burned
in the spring or summer, sprouting will be stimulated either way, and should be burned
60
for 30 s instead of 40 s to reduce the amount of time in the field. Some stump sprouts of
honeysuckle and privet were burned. Continued burning of the sprouts should continue
for both species to determine if this method can successfully eradicate the species from a
site. Reports have indicated repeated burning of Chinese privet will eliminate it over time
(Batcher 2000).
Although this method of control is effective at causing mortality in an already
established invasive site and may be just as effective in causing mortality in stump
sprouts with continued burning over time. It would be best to apply this method as soon
as these species appear in a stand. Managers or landowners can most effectively control
these species in a short amount of time and with little effort if they eradicate them before
these species begin reproducing. Lonicera maackii population growth is slow for the first
10 years (Deering and Vankat 1999). Most of the plants reproduce by age 5, so the
authors recommend control of this species to be conducted during this lag phase.
The cost for the equipment used was a total of $92.95. The torch cost was $63.00
and the propane tank $29.95. Assuming labor wages at $7.25/hr the approximate cost for
supplies and labor for burning was $0.43 per honeysuckle bush, $1.09 per privet plant,
and $1.46 per paulownia tree. This study was not conducted with the intent to give an
exact cost of using this method. My cost is a rough estimate of the time spent burning
individual plants for all species, although this was not recorded. My recommendation for
future studies of this method would be to develop a more precise cost. Also
recommended is focusing burning on only one invasive species at a time, and in different
habitat types, in order to determine if this method is efficient in causing similar mortality
in the various habitats. Additionally, another recommendation is continuing burning the
61
sprouts until the plant is unable to produce anymore sprouts to determine how many
annual burns it would take to eradicate a particular species from an area.
62
REFERENCES
Acquavella, J. F. Alexander, B. H. Mandel, J. S. Gustin, C. Baker, B. Chapman, P. and
Bleeke, M. 2004. Glyphosate biomonitoring for farmers and their families: results
from the farm family exposure study. Environmental Health Perspectives 112:
321-326.
Akerson, J. Gounaris, K. and Rafking, C. 2000. Strategic plan for managing alien
invasive vegetation. Colonial National Historic Park. Yorktown, Virginia.
Alabama Invasive Plant Council. 2007. Rescuing and preserving our natural heritage.
http://www.se-eppc.org/alabama/2007plantlist.pdf Accessed on 02-13-2011.
Barnes, W. J. and Cottam, G. 1974. Some autecological studies of the Lonicera X Bella
Complex. Ecology 55: 40-50.
Bartlow, J. Johnson, K. Kertis, M. Remaley, T. Ross, S. Simet, E. Soehn, D. and Taylor,
G. 1997. Tennessee exotic plant management manual.
Batcher, M. S. 2000. Element stewardship abstract for Ligustrum spp. privet. The Nature
Conservancy’s Wildland Invasive Species Program, Dept of Vegetable Crops &
Weed Sciences, University of California, Davis, CA.
Bowen, B. J. and Pate, J. S. 1993. The significance of root starch in post-fire shoot
recovery of the resprouter Stirlinga latifolia R. Br. (Proteaceae). Annals of Botany
72: 7-16.
Brown, C. E. and Pezeshki, R. S. 2000. A study on waterlogging as a potential tool to
control Ligustrum sinense populations in western Tennessee. Wetlands 20: 429437.
Burton, M. L. Samuelson, L. J. and Pan, S. 2005. Riparian woody plant diversity and
forest structure along an urban-rural gradient. Urban Ecosystems 8: 93-106.
Callaway, R. M. DeLuca, T. H. and Belliveau, W. M. 1999. Biological-control herbivores
may increase competitive ability of the noxious weed Centaurea maculosa.
Ecology 80: 1196-1201.
Cipollini, K. Ames, E. and Cipollini, D. 2009. Amur honeysuckle (Lonicera maackii)
management method impacts restoration of understory plants in the presence of
white-tailed deer (Odocoileus virginiana). Invasive Plant Science and
Management 2: 45-54.
63
Cohen, O. Riov, J. Katan, J. Gamliel, A. and Kutiel, P. B. 2008. Reducing persistent seed
banks of invasive plants by soil solarization – the case of Acacia saligna. Weed
Science 56: 860-865.
Collier, M. H. and Vankat, J. L. 2002. Diminished plant richness and abundance below
Amur honeysuckle, an invasive shrub. The American Midland Naturalist 147: 6071.
Deering, R. H. and Vankat, J. L. 1999. Forest colonization and developmental growth of
the invasive shrub Lonicera maackii. American Midland Naturalist 141: 43-50.
Ditomaso, J. M. 2000. Invasive weeds in rangelands: species, impacts, and management.
Weed Science. 48: 255-265.
Dorning, M. and Cipollini, D. 2005. Leaf and root extracts of the invasive shrub, Amur
honeysuckle, inhibit seed germination of three herbs with no autotoxic effects.
Plant Ecology 184: 287-296.
Drake, S. J. Weltzin, J. F. and Parr, P. D. 2003. Assessment of non-native invasive plant
species of the United States Department of Energy Oak Ridge National
Environmental Research Park. Castanea 68: 15-30.
Evans, C. W. Moorhead, D. J. Bargeron, C. T. and Douce, G. K. 2006. Invasive plant
responses to silvicultural practices in the south. The University of Georgia
Bugwood Network, Tifton GA, BW-2006-03. 52p.
Faulkner, J. L. Clebsch, E. E. C. and Sanders, W. L. 1989. Use of prescribed burning for
managing natural historic resources in Chickamauga and Chattanooga National
Flory, S. L. and Clay, K. 2005. Invasive shrub distribution varies with distance to roads
and stand age in eastern deciduous forests in Indiana, USA. Plant Ecology 184:
131-141.
Goodwin, B. J. McAllister, A. J. and Fahrig, L. 1999. Predicting invasiveness of plant
species based on biological information. Conservation Biology 13: 422-426.
Gorchov, D. L. and Trisel, D. E. 2003. Competitive effects of the invasive shrub, Amur
honeysuckle (Rupr.) herder (Caprifoliaceae), on the growth and survival of native
tree seedlings. Plant Ecology 166: 13-24.
Green, R. L. and Newell, A. L. 1982. Using goats to control brush regrowth on
fuelbreaks. USDA. Pacific Southwest Forest and Range Experiment Station.
Groves, R. H. 1989. Ecological control of invasive terrestrial plants. Biological
Invasions: a Global Perspective. John Wiley and Sons Chapter 20: 437-461.
Hanby, K. 2005. Alabama prescribed burning guide. Alabama Forestry Commission.
64
Hanula, J. L. Horn, S. 2011. Removing an invasive shrub (Chinese privet) increases
native bee diversity and abundance in riparian forests of the southeastern United
States. Insect Conservation and Diversity 10:1752-4598.
Hanula, J. L. Horn, S. and Taylor, J. W. 2009. Chinese privet (Ligustrum sinense)
removal and its effect on native plant communities of riparian studies. Invasive
Plant Science and Management 2: 292-300.
Harrington, M. G. 1993. Predicting Pinus ponderosa mortality from dormant season and
growing season fire injury. Int. J. Wildland Fire 3(2): 65-72.
Harrington, T. B. and Miller, J. H. 2005. Effects of application rate, timing, and
formulation of Glyphosate and Triclopyr on control of Chinese privet (Ligustrum
sinense). Weed Technology 19: 47-54.
Hartman, K. M. and McCarthy, B. C. 2004. Restoration of a forest understory after the
removal of an invasive shrub, amur honeysuckle (Amur honeysuckle).
Restoration Ecology 12: 154-165.
Heffernan, K. E. 1998. Managing invasive alien plants in natural areas, parks, and small
woodlands. National heritage technical report 98-25. Virginia Department of
Conservation and Recreation, Division of Natural Heritage. Richmond Virginia.
Herman, D. E. and Davidson C. G. 1997. Evaluation of Lonicera taxa for honeysuckle
aphid susceptibility, winter hardiness and use. Journal of Environmental
Horticulture 15(4):177-182.
Hobbs, R. J. and Humphries, S. E. 1995. An integrated approach to the ecology and
management of plant invasions. Conservation Biology: 761-770.
Hutchinson, T. F. and Vankat, J. L. 1997. Invasibility and effects of amur honeysuckle in
southwestern Ohio forests. Conservation Biology 11: 1117-1124.
Ingold, J. L. and Graycraft, M. J. 1983. Avian frugivory on honeysuckle (Lonicera) in
southwestern Ohio in fall. Ohio Journal of Science 83: 256-258.
Jiraungkoorskul, W. Upatham, E. S. Kruatrachue, M. Sahaphong, S. Vichasri-Gram, S.
and Pokethitiyook, P. 2002. Histopathological effects of Roundup, a Glyphosate
herbicide, on Nile tilapia (Oreochromis niloticus). ScienceAsia 28: 121-127.
Keeley, J. E. 2006. Fire management impacts on invasive plants in the western United
States. Conservation Biology 20: 375-384.
Kentucky Exotic Plant Council. 2008. Invasive exotic plant list [online]. Center for
Invasive Species and Ecosystem Health. http://www.se-eppc.org/ky/list.htm
Accessed on 02-13-2011.
65
Kline, V. M. and McClintock, T. 1994. Effect of burning on a dry oak forest infested with
woody exotics. Proceedings of the Thirteenth North American Prairie Conference
207-214.
Knopf, A. A. 2003. National Audubon Society: Field guide to trees eastern region. New
York, NY: Chanticleer Press.
Love, J. P. and Anderson, J. T. 2009. Seasonal effects of four control methods on the
invasive Morrow’s honeysuckle (Lonicera morrowii) and initial responses of
understory plants in a southwestern Pennsylvania old field. Restoration Ecology
17: 549-559.
Luginbuhl, J. M. Green, J. T. Poore, M. H. and Mueller, J. P. 1996. Use of goats as
biological agents for the control of unwanted vegetation. Department of Animal
Science, North Carolina State University. http://www.cals.ncsu.edu/an_sci/extensi
on/animal/meatgoat/MGVeget.htm Accessed on 11-11-10.
Luken, J. O. 1998. Population structure and biomass allocation of the naturalized shrub
Lonicera maackii (Rupr.) Maxim. in forests and open habitats. American Midland
Naturalist 119: 258-267.
Luken, J. O. and Mattimiro, D. T. 1991. Habitat-specific resilience of the invasive shrub
amur honeysuckle (Amur honeysuckle) during repeated clipping. Ecological
Applications 1: 104-109.
Luken, J. O. and Thieret, J. W. 1996. Amur honeysuckle, its fall from grace. BioScience
46: 18-24.
Masters, R. A. and Sheley, R. L. 2001. Invited synthesis paper: principles and practices
for managing rangeland invasive plants. Journal of Range Management 54: 502517.
McCaffrey, S. M. 2006. Prescribed fire: What influences public approval? Fire in eastern
oak forests: delivering science to land managers proceedings of a conference.
Gen. Tech. Rep. NRS-P-1. USDA Forest Service Northern Research Station. 192198.
McCarthy, B. 2005. Ecology of invasive species in southern Ohio: A tale of four species.
Department of Environmental and Plant Biology Ohio University, Athens, Ohio.
Ohio Invasive Plant Research Conference Proceedings.
McEwan, R. W. Birchfield, M. K. Schoergendorfer, A. and Arthur, M. A. 2009. Leaf
phenology and leaf tolerance of the invasive shrub amur honeysuckle and
potential native competitors. Journal of the Torrey Botanical Society 136: 212220.
66
Miller, J.H. 2003. Nonnative invasive plants of Southern forests: a field guide for
identification and control. USDA Forest Service Southern SRS-62. 93p.
Miller, J. H. 2007. Nonnative invasive plants of southern forests: A field guide for
identification and control. United States Department of Agriculture, Southern
Research Station, Asheville, NC.
Morris, L. L. Walck, J. L. and Hidayati, S. N. 2002. Growth and reproduction of the
invasive Ligustrum sinense and native Forestiera ligustrina (Oleacea):
implications for the invasion and persistence of the nonnative shrub. International
Journal of Plant Sciences 163: 1001-1010.
Neumann, G. Kohls, S. Landsberg, E. Stock-Olivera Souza, K. Yamada, T. and Romheld
V. 2006. Relevance of glyphosate transfer to non-target plants via the rhizosphere.
Journal of Plant Diseases and Protection 963-969.
Paganelli, A. Gnazzo, V. Acosta H. Lopez S. L. and Carrasco A. E. 2010. Glyphosatebased herbicides produce teratogenic effects on vertebrates by impairing retinoic
acid signaling. Chem. Res. Toxicol 23: 1586-1595.
Paynter, Q. and Flanaga, G. J. 2004. Integrating herbicide and mechanical control
treatments with fire and biological control to manage an invasive shrub, Mimosa
pigra. Journal of Applied Ecology 41: 615-629.
Peluso, M. Munnia, A. Bolognesi, C. and Parodi, S. 1998. P-postlabeling detection of
DNA adducts in mice treated with the herbicide Roundup. Environmental and
Molecular Mutagenesis 31: 55-59.
Pimentel, D. Lach, L. Zuniga, R. and Morrison D. 1999. Environmental and economic
costs associated with non-indigenous species in the United States. BioScience 50:
53-65.
Pond, F. W. and Cable, D. R. 1961. Effect of heat treatment on sprout production of some
shrubs of the chaparral in central Arizona. Range Conservationists, Rocky
Mountain Forest and Range Experiment Station, USDA Forest Service 313-317.
Relyea, R. A. 2005. The lethal impact of roundup on aquatic and terrestrial
amphibians.Ecological Society of America 15: 1118-1124.
Remaley, T. 2005. Fact sheet: princess tree. Plant Conservation Alliance’s Alien Plant
Working Group. http://www.nps.gov/plants/alien/ Accessed on 10-19-10.
Richard, S, Moslemi, S. Sipahutar, H. Benachour, N. and Seralini, G.E. 2005. Differential
effects of glyphosate and roundup on human placental cells and aromatase.
Environmental Health Perspectives 113: 716-720.
67
Richburg, J.A. and W.A. Patterson III. 2003. Can northeastern woody invasive plants be
controlled with cutting and burning treatments? Proceedings, Using Fire to
Control Invasive Plants: What’s New, What Works in the Northeast? Portsmouth,
NH: University of New Hampshire Cooperative Extension. Pp.1-3.
Sheley, R. Manoukian, M. and Marks, G. 1996. Preventing noxious weed invasion.
Rangelands 18: 100-101.
Stachowski-Haberkorn, S. Becker, B. Marie, D. Haberkorn, H. Coroller, L. and de la
Broise, D. 2008. Impact of roundup on the marine microbial community, as
shown by an in situ microcosm experiment. Aquatic Toxicology 89: 232-241.
Stapelton, J. J. and De Vay, J. E. 1982. Effect of soil solarization on populations of
selected soilborne microorganisms and growth of deciduous fruit tree seedlings.
Disease Control and Pest Management Phytopathology 72: 323-236.
Stephens, S. L. and Ruth, L. W. 2005. Federal forest fire policy in the United States. Fire
Management 22: 57-77.
TNEPPC. 2010. Lonicera fragrantissima Lindl. & Paxton. Tennessee Exotic Pest Plant
Council. http://www.tneppc.org/invasive_plants/28 accessed on 12-30-10.
Trlica, M. J. Jr. and Cook, C. W. 1971. Defoliation effects on carbohydrate reserves in
desert species. J. Range Management 24: 418-25.
Tu, M. Hurd, C. and Randall, J. M. 2001. Weed control methods handbook: tools and
techniques for use in natural areas. The Nature Conservancy.
Tveten, R. K. and Fonda, R. W. 1999. Fire effects on prairies and oak woodlands on Fort
Lewis, Washington. Northwest Science 73: 145-158.
Ulyshen, M. D. Horn, S. and Hanula, J. L. 2010. Response of beetles (Coleoptera) at
three heights to the experimental removal of an invasive shrub, Chinese privet
(Ligustrum sinense), from floodplain forests. Biological Invasions 12: 1573-1579.
Urbatsch, L. 2010. Plant guide: Chinese privet. United States Department of Agriculture,
Natural Resource Conservation Science. Louisiana State University. Baton
Rouge, Louisiana. http://plants.usda.gov/plantguide/pdf/pg_lisi.pdf Accessed on
08-12-10.
USDA Forest Service. 2005. Forest invasive plant resources. Northern Area State and
Private Forestry. United States Department of Agriculture Forest Service. http://n
a.fs.fed.us/spfo/invasiveplants/factsheets/pdf/bush-honeysuckle.pdf accessed on
01-14-11.
Vermeire, L. T. and Rinella, M. J. 2009. Fire alters emergence of invasive plant species
from soil surface-deposited seeds. Weed Science 57: 304-310.
68
Walsh, L.P., McCormick, C., Martin C., and Stocco D.M. 2000. Roundup inhibits
steroidogenesis by disrupting steroidogenic acute regulatory (StAR) protein
expression. Environmental Health Perspectives 108: 769-776.
Wilcove, D. S. Rothstein, D. Bubow, J. Phillips, A. and Losos, E. 1998. Quantifying
threats to imperiled species in the United States. Bioscience 48 (8): 607-615.
Wilgen, B. V. Richardson, D. and Higgins, S. 2001. Integrated control of invasive alien
plants in terrestrial ecosystems. Land Use and Water Resources Research 1: 1-6.
Wright, B. J. and Clarke, P. J. 2007. Resprouting responses of Acacia shrubs in the
western desert of Australia – fire severity, interval and season influence survival.
International Journal of Wildland Fire 16: 317-323.
Zhang, Y. Hanula, J. L. and Sun, J. 2008. Host specificity of Argopistes tsekooni
(Coleoptera: Chrysomelidae), a potential biological control agent of Chinese
Privet. Journal of Economic Entomology 101: 1146-1151.
Zhao-hua, Z. Ching-Ju, C. Xin-Yu, L. and Gao, X. Y. 1986. Paulownia in China:
cultivation and utilization. Asian Network for Biological Sciences and
International Development Research Centre.
69