Critique 1
Affects of Density on Intraspecific Competition in Marigolds
Eric W. Flatt
Tennessee Tech University, Cookeville 38505, Tennessee
Abstract. The purpose of this study was to see whether density had any effect on
intraspecific competition in marigolds. My objective with this study was to prove that
density does have an affect on intraspecific competition in marigolds. I tested the
hypothesis that density does affect intraspecific competition in marigolds by setting up
six pots with different densities of marigolds in each pot. After five weeks, the marigolds
were weighed and measured for their survivorship, total weight, mean weight, mean stem
weight, mean leaf weight, mean stem length, and mean growth rate. Each of these were
then placed into a scatter plot comparing the results of each versus the density of
marigolds in each pot. The results showed that plant density did have an affect on
intraspecific competition in marigolds. The results I obtained are consistent with other
studies and show how not just marigolds, but all plants are affected by their densities and
thus, need to be in habitats that are less dense so they can grow at optimum health.
Key Words: intraspecific competition, Marigolds
Introduction
Plant competition has been the object of ecologists’ studies for several years.
Numerous and exhausting questions have been raised regarding plant competition. Most
experimental studies in plant competition over the past several years have involved
manipulating the densities of one or more plant species and quantifying the response of
other plants (Miller 1990). A great deal of research has been devoted to understanding
how plant species effect and respond to each other and how the interactions effect the
dynamics, structure, and evolution of the plants in the vicinity (Connolly 2001).
Dissimilarity in plant responses to neighbors of the same species may influence the
distribution and abundance of the species in differing environments. The ability of a plant
to endure the suppression of its neighbors often varies among species (Peltzer and Wilson
2001).
During intraspecific competition, plants tend to respond with resource allocation.
For many species, a density increase results in total weight, height, reproduction and/or
survival decrease (Lentz 1999). Individual plants are not the only things affected by
intraspecific competition. Entire groups are affected and tend to form a hierarchy based
on size; this being where a few individuals contribute most of the population’s biomass
and most of the individuals are relatively small (Lentz 1999). In this experiment, I studied
and recorded data on intraspecific competition in marigolds. My objective for this
experiment was to be able to prove that density does have an affect on intraspecific
competition in plants. My null hypothesis for this experiment was that density will not
affect the measurements used to answer this question.
Methods
Plant competition experiments have been done in several ways, but I could not
find an article that had an experiment conducted the way I wanted to do mine or that
could have been done in the amount of time I had to get my experiment done. So, in my
experiment I manipulated the density of marigolds as described by Miller (Miller 1990). I
planted marigolds in six pots at densities of 2, 4, 8, 16, 32, and 64 per pot. I labeled each
pot so that I would know which was which and checked them for growth and
development each week. They were also watered only once a week at the same time and
on the same day of each week. Then after five weeks, I measured and weighed the
marigolds for their plant density, survivorship, total weight, mean weight, mean stem
weight, mean leaf weight, mean stem length, and mean growth rate for the plants of each
pot. These data were recorded in the data form (Table 1). Then graphs were constructed
showing plant density versus mean plant weight, total plant weight, stem length, mean
stem weight, mean leaf weight, mean growth rate per plant, and survivorship.
Results
Mean Plant Weight (mg)
Plant Density vs. Mean Plant Weight
80
70
60
50
40
Avg Wt
30
20
10
0
0
20
40
60
80
Plant Density
Fig. 1: The mean marigold weight for each density treatment after five weeks.
Total Plant Weight (mg)
Plant Density vs. Total Plant Weight
3000
2500
2000
1500
Total Wt
1000
500
0
0
20
40
60
80
Plant Density
Fig. 2: The total weight of all the marigolds in each density treatment.
Plant Density vs. Plant Height
Plant Height (cm)
5
4
3
Avg Stem Length
2
1
0
0
50
100
Plant Density
Fig. 3: The average marigold height in each density treatment after five weeks.
Mean Stem Weight (mg)
Plant Density vs. Mean Stem Weight
25
20
15
Avg Stem Wt
10
5
0
0
20
40
60
80
Plant Density
Fig. 4: The average stem weight of each marigold in each density treatment after five
weeks.
Plant Density vs. Mean Leaf Weight
Mean Leaf Weight (mg)
60
50
40
30
Avg Leaf Wt
20
10
0
0
20
40
60
80
Plant Density
Fig. 5: The average leaf weight of the marigolds in each density treatment after five
weeks.
Mean Growth Rate Per
Plant (cm per day)
Plant Density vs. Mean Growth Rate
Per Plant
0.12
0.1
0.08
0.06
Avg Growth Rate
0.04
0.02
0
0
50
100
Plant Density
Fig. 6: The average growth of the marigolds in each density treatment after five weeks.
% Survival
Plant Density vs. % Survival
101
100
99
98
97
96
95
94
93
92
91
% Survival
0
20
40
60
80
Plat Density
Fig. 7: The survival percentage for the marigolds in each density treatment after five
weeks.
Discussion
The results showed a slight decrease in survivorship as the density of marigolds in
each pot increased. The results also showed that as the density of marigolds in each pot
increased the average weight of the marigolds decreased, but the average height of the
marigolds increased as the density increased. Thus, the marigolds seem to be forced to
compete harder for light as the density increases and are focusing all their energy into
growing as high as possible. The marigolds did have a decrease in mean leaf and stem
weight as density increased which was also shown by Lentz (Lentz 1999). However,
there did not seem to be any definite size hierarchy among the marigolds as found by
Lentz (Lentz 1999).
Conclusions
 Density did have an affect on the intraspecific competition between the marigolds.
 The higher the density is the more plants such as marigolds are forced to compete for
limited resources in the area.
 Low densities are more beneficial to the survival and health of marigolds.
 Future research will have to be done to see what the long term results are when
marigolds are forced to face a higher density as opposed to a lower density in a
confined amount of space.
Acknowledgements
I would like to thank Dr. Brown for his help and insight into helping me conduct
this experiment and organize the data.
Literature Cited
Connolly, John, Peter Wayne and Fakhri A. Bazzazz. 2001. Interspecific Competition in
Plants: How Well Do Current Methods Answer Fundamental Questions? The
American Naturalist 157: 107.
Grace, James B. 1995. On the Measurement of Plant Competition Intensity. Ecology 76:
305-308.
Lentz, Kendra A. 1999. Effects of Intraspecific Competition and Nutrient Supply on the
Endangered Northeastern Bulrush, Scirpus Ancistrchaetus Schuyler (Cyperaceae).
The American Midland Naturalist 142: 47-54.
Miller, Thomas E. 1990. Perspectives on Plant Competition. Science 249: 1054.
Peltzer, Duane A., Scott D. Wilson. 2001. Variation in Plant Responses to Neighbors at
Local and Regional Scales. The American Naturalist 157: 610.
Thompson, K. 1987. The Resource Ratio Hypothesis and the Meaning of Competition.
Functional Ecology 1: 297-303.
Add Appendix and Data Form
Critique 2
Affects of Density on Intraspecific Competition in Marigolds
Eric W. Flatt
Tennessee Tech University, Cookeville 38505, Tennessee
Abstract.(make abstract a heading) The purpose of this study was to see whether density
had any effect on intraspecific competition in marigolds. My objective with this study
was to prove that density does have an affect on intraspecific competition in marigolds. I
tested my hypothesis that density does affect intraspecific competition in marigolds by
setting up six pots with different densities of marigolds in each pot. After five weeks, the
marigolds were weighed and measured for their survivorship, total weight, mean weight,
mean stem weight, mean leaf weight, mean stem length, and mean growth rate. Each of
these was then placed into a scatter plot comparing the results of each versus the density
of marigolds in each pot. The results showed that plant density did have an affect on
intraspecific competition in marigolds. The results I obtained are consistent with other
studies and show how not just marigolds, but all plants are affected by their densities and
thus, need to be in habitats that are less dense so they can grow at optimum health.
Key Words: intraspecific competition, Marigolds
Introduction (need another article cited)
Plant competition has been the object of ecologists’ studies for several years.
Numerous and exhausting questions have been raised regarding plant competition. Most
experimental studies in plant competition over the past several years have involved
manipulating the densities of one or more plant species and quantifying the response of
other plants (Miller 1990). A great deal of research has been devoted to understanding
how plant species affect and respond to each other and how the interactions affect the
dynamics, structure, and evolution of the plants in the vicinity (Connolly 2001).
Dissimilarity in plant responses to neighbors of the same species may influence the
distribution and abundance of the species in differing environments. The ability of a plant
to endure the suppression of its neighbors often varies among species (Peltzer and Wilson
2001).
During intraspecific competition, plants tend to respond with resource allocation.
For many species, a density increase results in total weight, height, reproduction and/or
survival decrease (Lentz 1999). Individual plants are not the only things affected by
intraspecific competition. Entire groups are affected and tend to form a hierarchy based
on size; this being where a few individuals contribute most of the population’s biomass
and most of the individuals are relatively small (Lentz 1999). In this experiment, I studied
and recorded data on intraspecific competition in marigolds. My objective for this
experiment was to be able to prove that density does have an affect on intraspecific
competition in plants. My null hypothesis for this experiment was that density will not
affect the measurements used to answer this question.
Methods
Plant competition experiments have been done in several ways, but I could not
find an article that had an experiment conducted the way I wanted to do mine or that
could have been done in the amount of time I had to get my experiment done. So, in my
experiment I manipulated the density of marigolds as described by Miller (Miller 1990). I
planted marigolds in six pots at densities of 2, 4, 8, 16, 32, and 64 per pot. I labeled each
pot so that I would know which was which and checked them for growth and
development each week. They were also watered only once a week at the same time and
on the same day of each week. Then after five weeks, I measured and weighed the
marigolds for their plant density, survivorship, total weight, mean weight, mean stem
weight, mean leaf weight, mean stem length, and mean growth rate for the plants of each
pot. These data were recorded in the data form (Table 1). Then I constructed graphs
showing plant density versus mean plant weight, total plant weight, stem length, mean
stem weight, mean leaf weight, mean growth rate per plant, and survivorship.
Results
Mean Plant Weight (mg)
Plant Density vs. Mean Plant Weight
80
70
60
50
40
Avg Wt
30
20
10
0
0
20
40
60
80
Plant Density
Fig. 1: The mean marigold weight for each density treatment after five weeks.
Total Plant Weight (mg)
Plant Density vs. Total Plant Weight
3000
2500
2000
1500
Total Wt
1000
500
0
0
20
40
60
80
Plant Density
Fig. 2: The total weight of all the marigolds in each density treatment.
Plant Density vs. Plant Height
Plant Height (cm)
5
4
3
Avg Stem Length
2
1
0
0
50
100
Plant Density
Fig. 3: The average marigold height in each density treatment after five weeks.
Mean Stem Weight (mg)
Plant Density vs. Mean Stem Weight
25
20
15
Avg Stem Wt
10
5
0
0
20
40
60
80
Plant Density
Fig. 4: The average stem weight of each marigold in each density treatment after five
weeks.
Plant Density vs. Mean Leaf Weight
Mean Leaf Weight (mg)
60
50
40
30
Avg Leaf Wt
20
10
0
0
20
40
60
80
Plant Density
Fig. 5: The average leaf weight of the marigolds in each density treatment after five
weeks.
Mean Growth Rate Per
Plant (cm per day)
Plant Density vs. Mean Growth Rate
Per Plant
0.12
0.1
0.08
0.06
Avg Growth Rate
0.04
0.02
0
0
50
100
Plant Density
Fig. 6: The average growth of the marigolds in each density treatment after five weeks.
% Survival
Plant Density vs. % Survival
101
100
99
98
97
96
95
94
93
92
91
% Survival
0
20
40
60
80
Plat Density
Fig. 7: The survival percentage for the marigolds in each density treatment after five
weeks.
Discussion (need 4 more articles cited and more discussion if possible)
My results showed a slight decrease in survivorship as the density of marigolds in
each pot increased. My results also showed that as the density of marigolds in each pot
increased the average weight of the marigolds decreased, but the average height of the
marigolds increased as the density increased. Thus, the marigolds seem to be forced to
compete harder for light as the density increases and are focusing all their energy into
growing as high as possible. The marigolds did have a decrease in mean leaf and stem
weight as density increased which was also shown by Lentz (Lentz 1999). However,
there did not seem to be any definite size hierarchy among the marigolds as found by
Lentz (Lentz 1999).
Conclusions
 Density did have an affect on the intraspecific competition between the marigolds.
 The higher the density is the more plants such as marigolds are forced to compete for
limited resources in the area.
 Low densities are more beneficial to the survival and health of marigolds.
 (future research is not bulleted only conclusions from this study)Future research will
have to be done to see what the long term results are when marigolds are forced to
face a higher density as opposed to a lower density in a confined amount of space.
Acknowledgements (does not need to be double spaced)
I would like to thank Dr. Brown for his help and insight into helping me conduct
this experiment and organize the data.
Literature Cited
Connolly, John, Peter Wayne and Fakhri A. Bazzazz. 2001. Interspecific Competition in
Plants: How Well Do Current Methods Answer Fundamental Questions? The
American Naturalist 157: 107.
Grace, James B. 1995. On the Measurement of Plant Competition Intensity. Ecology 76:
305-308.
Lentz, Kendra A. 1999. Effects of Intraspecific Competition and Nutrient Supply on the
Endangered Northeastern Bulrush, Scirpus Ancistrchaetus Schuyler (Cyperaceae).
The American Midland Naturalist 142: 47-54.
Miller, Thomas E. 1990. Perspectives on Plant Competition. Science 249: 1054.
Peltzer, Duane A., Scott D. Wilson. 2001. Variation in Plant Responses to Neighbors at
Local and Regional Scales. The American Naturalist 157: 610.
Thompson, K. 1987. The Resource Ratio Hypothesis and the Meaning of Competition.
Functional Ecology 1: 297-303.
Critique 3
Affects of Density on Intraspecific Competition in Marigolds
Eric W. Flatt
Tennessee Tech University, Cookeville 38505, Tennessee
Abstract. The purpose of this study was to see whether density had any effect on
intraspecific competition in marigolds. My objective with this study was to prove that
density does have an affect on intraspecific competition in marigolds. I tested my
hypothesis that density does affect intraspecific competition in marigolds by setting up
six pots with different densities of marigolds in each pot. After five weeks, the marigolds
were weighed and measured for their survivorship, total weight, mean weight, mean stem
weight, mean leaf weight, mean stem length, and mean growth rate. Each of these was
then placed into a scatter plot comparing the results of each versus the density of
marigolds in each pot. The results showed that plant density did have an affect on
intraspecific competition in marigolds. The results I obtained are consistent with other
studies and show how not just marigolds, but all plants are affected by their densities and
thus, need to be in habitats that are less dense so they can grow at optimum health.
Key Words: intraspecific competition, Marigolds
Introduction
Plant competition has been the object of ecologists’ studies for several years.
Numerous and exhausting questions have been raised regarding plant competition. Most
experimental studies in plant competition over the past several years have involved
manipulating the densities of one or more plant species and quantifying the response of
other plants (Miller 1990). A great deal of research has been devoted to understanding
how plant species affect and respond to each other and how the interactions affect the
dynamics, structure, and evolution of the plants in the vicinity (Connolly 2001).
Dissimilarity in plant responses to neighbors of the same species may influence the
distribution and abundance of the species in differing environments. The ability of a plant
to endure the suppression of its neighbors often varies among species (Peltzer and Wilson
2001).
During intraspecific competition, plants tend to respond with resource allocation.
For many species, a density increase results in total weight, height, reproduction and/or
survival decrease (Lentz 1999). Individual plants are not the only things affected by
intraspecific competition. Entire groups are affected and tend to form a hierarchy based
on size; this being where a few individuals contribute most of the population’s biomass
and most of the individuals are relatively small (Lentz 1999). In this experiment, I studied
and recorded data on intraspecific competition in marigolds. My objective for this
experiment was to be able to prove that density does have an affect on intraspecific
competition in plants. My null hypothesis for this experiment was that density will not
affect the measurements used to answer this question.
Methods
Plant competition experiments have been done in several ways, but I could not
find an article that had an experiment conducted the way I wanted to do mine or that
could have been done in the amount of time I had to get my experiment done. So, in my
experiment I manipulated the density of marigolds as described by Miller (Miller 1990). I
planted marigolds in six pots at densities of 2, 4, 8, 16, 32, and 64 per pot. I labeled each
pot so that I would know which was which and checked them for growth and
development each week. They were also watered only once a week at the same time and
on the same day of each week. Then after five weeks, I measured and weighed the
marigolds for their plant density, survivorship, total weight, mean weight, mean stem
weight, mean leaf weight, mean stem length, and mean growth rate for the plants of each
pot. These data were recorded in the data form (Table 1). Then I constructed graphs
showing plant density versus mean plant weight, total plant weight, stem length, mean
stem weight, mean leaf weight, mean growth rate per plant, and survivorship. (add Fig.
numbers)
Results
Mean Plant Weight (mg)
Plant Density vs. Mean Plant Weight
80
70
60
50
40
Avg Wt
30
20
10
0
0
20
40
60
80
Plant Density
Fig. 1: The mean marigold weight for each density treatment after five weeks.
Total Plant Weight (mg)
Plant Density vs. Total Plant Weight
3000
2500
2000
1500
Total Wt
1000
500
0
0
20
40
60
80
Plant Density
Fig. 2: The total weight of all the marigolds in each density treatment.
Plant Density vs. Plant Height
Plant Height (cm)
5
4
3
Avg Stem Length
2
1
0
0
50
100
Plant Density
Fig. 3: The average marigold height in each density treatment after five weeks.
Mean Stem Weight (mg)
Plant Density vs. Mean Stem Weight
25
20
15
Avg Stem Wt
10
5
0
0
20
40
60
80
Plant Density
Fig. 4: The average stem weight of each marigold in each density treatment after five
weeks.
Plant Density vs. Mean Leaf Weight
Mean Leaf Weight (mg)
60
50
40
30
Avg Leaf Wt
20
10
0
0
20
40
60
80
Plant Density
Fig. 5: The average leaf weight of the marigolds in each density treatment after five
weeks.
Mean Growth Rate Per
Plant (cm per day)
Plant Density vs. Mean Growth Rate
Per Plant
0.12
0.1
0.08
0.06
Avg Growth Rate
0.04
0.02
0
0
50
100
Plant Density
Fig. 6: The average growth of the marigolds in each density treatment after five weeks.
% Survival
Plant Density vs. % Survival
101
100
99
98
97
96
95
94
93
92
91
% Survival
0
20
40
60
80
Plat Density
Fig. 7: The survival percentage for the marigolds in each density treatment after five
weeks.
Discussion (need more articles cited)
My results showed a slight decrease in survivorship as the density of marigolds in
each pot increased. My results also showed that as the density of marigolds in each pot
increased the average weight of the marigolds decreased, but the average height of the
marigolds increased as the density increased. Thus, the marigolds seem to be forced to
compete harder for light as the density increases and are focusing all their energy into
growing as high as possible. The marigolds did have a decrease in mean leaf and stem
weight as density increased which was also shown by Lentz (Lentz 1999). However,
there did not seem to be any definite size hierarchy among the marigolds as found by
Lentz (Lentz 1999).
Conclusions
 Density did have an affect on the intraspecific competition between the marigolds.
 The higher the density is the more plants such as marigolds are forced to compete for
limited resources in the area.
 Low densities are more beneficial to the survival and health of marigolds.
 Future research will have to be done to see what the long term results are when
marigolds are forced to face a higher density as opposed to a lower density in a
confined amount of space.
Acknowledgements
(This is not supposed to be double spaced) I would like to thank Dr. Brown for his
help and insight into helping me conduct this experiment and organize the data.
Literature Cited
Connolly, John, Peter Wayne and Fakhri A. Bazzazz. 2001. Interspecific Competition in
Plants: How Well Do Current Methods Answer Fundamental Questions? The
American Naturalist 157: 107.
Grace, James B. 1995. On the Measurement of Plant Competition Intensity. Ecology 76:
305-308.
Lentz, Kendra A. 1999. Effects of Intraspecific Competition and Nutrient Supply on the
Endangered Northeastern Bulrush, Scirpus Ancistrchaetus Schuyler (Cyperaceae).
The American Midland Naturalist 142: 47-54.
Miller, Thomas E. 1990. Perspectives on Plant Competition. Science 249: 1054.
Peltzer, Duane A., Scott D. Wilson. 2001. Variation in Plant Responses to Neighbors at
Local and Regional Scales. The American Naturalist 157: 610.
Thompson, K. 1987. The Resource Ratio Hypothesis and the Meaning of Competition.
Functional Ecology 1: 297-303.
Appendix
Density
# of survivals
Total weight
(mg)
Average
Weight (mg)
Total Stem
weight
(mg)
Average
Stem weight
(mg)
Average Leaf
Weight (mg)
Average
stem length
(cm)
Average
Growth Rate
(cm per day)
% survival
Table A: Intraspecific Competition Data
2
4
8
16
32
2
4
8
16
31
100
280
540
1030
1570
50
70
67.5
64.375
50.645
30
80
170
290
450
15
20
21.25
18.125
14.516
35
50
46.25
46.25
36.13
1.68
1.68
3.99
3.99
3.99
0.04
0.04
0.095
0.095
0.095
100
100
100
100
96.8
64
59
2670
45.254 850
14.407
30.85
4.49
0.107
92.2