1. Effects of plant competition on shoot versus root growth and soil microbial activity in
brownfield versus allotment soils
Abstract
Self/non-self discrimination has been studied as a below ground interaction in response to
both intraspecific competition and interspecific competition as resource control is established.
In this study, via the use of Timonen et al’s 1997 experimental design of testing root growth
responses to competition; the effects of two soil types were used to assess soil contamination
impacts and competition impacts on self/non-self discrimination. The findings of this study
were inconclusive and no significant impacts were recorded. Further testing and improvement
in experimental design is required.
Introduction
Optimal plant growth production is dependent on the availability of resources such as soil
nutrients and water. The abundance of root mass is dictated by the accessibility of resources,
as roots actively pursue these resources within the soil (Fitter & Hay 2002). As soil fertility
decreases, investment in root production is increased as the plant applies more surface area to
its search for resources (Nyakudya & Stroosnijder 2014). Investment in root production is
critical to the survival of plants faced with reduced access to resources which not only occurs
in low nutrient soils but also within environments where interspecific competition is abundant
(Craine & Dybzinski 2013). As all plants require the same fundamental resources, the
survival of a plant community is determined by the distribution of the available resources
either by partitioning or the establishment of a single dominant organism (Andrade et al
2014). Consequently belowground root interactions are critical not just for the success of a
plants production, but also for a plants establishment of its position within the community’s
hierarchy (Fort et al 2014). Self/non-self recognition in plants has been documented within
root interactions between both kin plants and interspecific plants (Chen et al 2012).
Observations have identified that belowground interactions are more sophisticated than
originally assumed in that plants increase root growth towards neighbours, consequently
increasing competition for resources; or invest in growth away from its neighbours to reduce
competition (Mahall & Callaway 1992). Interactions between kin plants also indicate plants
recognition of potential benefits of growing in close proximity to one another to mutually
benefit from the distribution of nutrients and soil microbes (Hamilton 1964). A study
performed by Mahall & Callaway in 1991 on desert shrubs found that shrubs of the same

2. species would reduce their root growth whenever the roots encountered the roots of another
shrub of the same species. However when roots of the same plant were encountered root
growth was not disrupted. It was determined that the reduction in root growth upon detection
of a same species neighbour, was an active trait used to reduce intraspecific competition for
water. Studies performed by the planting of same species and mixed species plants within
containers have also provided evidence that the presence of a non-self neighbour incurred a
response of increased root mass by up to 85% in contrast to containers which contained self
neighbours which only increased root mass by 30% (Gersani et al 2001).
In this study the hypotheses of self/non-self discrimination will be tested by the observation
of belowground interactions and biomass production of three species of plants, Lolium
perenne, Festuca ovina and Trifolium pratense; which will be exposed not only to
interspecific competition, but two different soil types. Soil microbial activity in both soil
types will also be tested to determine if activity is impacted by the soil type. The soils used in
this experiment were obtained from Abbey Hey allotments, Gorton, Manchester. Sample soils
were taken from a vegetable plot utilised in the production of produce for local residents and
a former scrap metal business plot which had discontinued over 40 years ago; with high
concentrations of soil metals considered harmful to human health and also of detriment to soil
quality.
Aims
To determine the interspecific competition impacts on plant productivity in two contrasting
soil types to test the hypothesis of self/non-self discrimination.
To measure the effects of soil type on species-specific plant production, determined by a total
plant fresh and a root versus shoot observation.
Plant species on soil microbial activity (FDA hydrolysis) responses in allotment and
contaminated brownfield soil
Method and materials
Lolium perenne, Festuca ovina and Trifolium pratense were selected for this investigation
due to the limitations of the study as to the time of year and time restrictions imposed to
conduct the study. Each species selected is relatively hardy with a quick growth rate and
ability to thrive in artificial growing conditions.

3. The experimental design used in this study mirrored that of the one used in Timonen et al’s
1997 of interactions between genets of Suillus spp and differen Pinus sylvestris genotype
combinations.
The experiment was initiated in October by the production of six plant pots to observe same
species interactions via the creation of pots containing one species per pot, per soil type. A
further two pots were created to observe belowground interspecific competition between the
three selected species by the creation of pots containing all three species per soil type. In
addition to this two control pots were produced separately containing only soil from the two
soil types. All experimental pots were then placed in a greenhouse under controlled
conditions to simulate climates ideal for growth. All pots were regularly watered and weeded
until the following January.
January harvest
In total 21 same species pots with vegetable plot soil were produced and 18 same species pots
with contaminated soil will produced. 12 competition pots with vegetable plot soil were
produced and 15 with contaminated soil were produced.
All the planted pots were then harvested by separation of each pots soil from its plants. From
the soil a 10 gram sample was taken from each pot for FDA hydrolysis activity.
Cutting and weighing
Following the techniques outlined by Timonen et al (1997) each plant was weighed to
determine its fresh shoot and root weight. Each plant was cut to separate its shoot and root,
which was then weighed and recorded to 4 decimal places. This process was repeated for the
roots and shoots for all pots in both soil types. After weighing all individual roots and all
individual shoots they were then dried at 80°C for 48 hours.
After 48 hours each root and shoot sample was then reweighed to determine its dry weight.

4. Results
AllotmentControl
Plantvariable T.pratense L. perenne F. ovina
ShootFreshwt (g)
2.33 ± 1.02
P= 0.416
0.33 ± 0.21
P= 0.009
0.05 ± 0.02
P=0.958
Root Fresh(g)
1.60 ± 0.83
P = 0.7446
0.51 ± 0.32
P= 0.060
0.12 ± 0.19
P= 0.000
Total PlantFreshwt(g)
3.93 ± 1.76
P= 0.804
0.84 ± 0.45
P= 0.029
0.18 ± 0.19
P= 0.00
ShootDry wt (g)
0.73 ± 0.84
P = 0.000
0.08 ± 0.32
P= 0.000
0.00 ± 0.00
P= 0.803
Root Dry wt (g)
0.54 ± 0.87
P= 0.000
0.05 ± 0.03
P= 0.112
0.01 ± 0.01
P= 0.098
Total PlantDry wt(g)
1.27 ± 1.71
P= 0.000
0.14 ± 0.14
P= 0.000
0.18 ± 0.01
P=0.508
Table 1. Allotment soil control sample analysis of mean ± SD and (Shapiro-Wilks) normality (P) per sample plant
species
Table 2. Contaminatedsoil control sample analysis of mean ± SD and (Shapiro-Wilks) normality (P) per sample plant
species
Analysis from table 1 (Allotment control samples) demonstrates a higher ratio of shoot
growth in T.pratense than root growth at approximately a shoot to root ratio (fresh weight) of
2:1. Whereas L. perenne and F. ovina both demonstrate a higher root growth ratio than shoot,
with L.perenne having a shoot to root ratios (fresh weight) of approx. 1.1 : 1.7 and F.ovina
1:2.4.
Contaminated Control
Plantvariable T.pratense L. perenne F. ovina
ShootFreshwt (g)
1.57 ± 1.19
P= 0.077
0.40 ± 0.14
P= 0.774
0.04 ± 0.02
P= 0.204
Root Fresh(g)
0.95 ± 0.70
P=0.033
0.65 ± 0.60
P= 0.012
0.08 ± 0.10
P= 0.000
Total PlantFreshwt(g)
2.52 ± 1.83
P= 0.118
1.05 ± 0.62
P= 0.101
0.12 ± 0.10
P= 0.024
ShootDry wt (g)
0.23 ± 0.16
P= 0.128
0.06 ± 0.03
P= 0.799
0.01 ± 0.01
P=0.000
Root Dry wt (g)
0.07 ± 0.05
P= 0.241
0.04 ± 0.03
P = 0.010
0.01 ± 0.01
P=0.000
Total PlantDry wt(g)
0.31 ± 0.20
P= 0.456
0.10 ± 0.51
P= 0.158
0.01 ± 0.13
P= 0.001

5. Analysis from table 2 (Contaminated soil samples) demonstrates a similar observation of
shoot growth in T.pratense with a shoot to root ratio (fresh weight) of approximately 1.9 :
1.18. However there is a notable increase in root growth within the L. perenne with a shoot to
root ratio (fresh weight) of 2: 3.3. The shoot to root ratio of F. ovina has slightly decreased
with a ratio of 1:2.
A Mann-Whitney U test concludes that the null hypothesis of “fresh root weight is the same
across both soil types” should be rejected with a P value of 0.049 occurring; identifying that
soil type has a significant impact on root growth of same species plant pots.
Overall comparisons between the two soil types indicate a notable decline in biomass per
species, with the allotment soil producing the greater amount of biomass. This is not true in
the case of L. perenne however which indicated an increase in growth within the
contaminated soil in comparison to the allotment soil.
AllotmentCompetition
Plantvariable T.pratense L. perenne F. ovina
ShootFreshwt (g)
2.75 ± 1.82
P= 0.560
0.50 ± 0.30
P= 0.139
0.03 ± 0.02
P = 0.512
Root Fresh(g)
1.66 ± 1.32
P = 0.282
0.92 ± 0.92
P= 0.040
0.03 ± 0.03
P= 0.024
Total PlantFreshwt(g)
4.41 ± 2.90
P= 0.549
1.43 ± 1.20
P= 0.059
0.06 ± 0.46
P= 0.022
ShootDry wt (g)
0.41 ±
0.26 P =
0.381
0.08 ± 0.06
P= 0.067
0.01 ± 0.01
P= 0.114
Root Dry wt (g)
0.14 ± 0.08
P= 0.926
0.05 ± 0.03
P = 0.100
0.01 ± 0.01
P=0.003
Total PlantDry wt(g)
0.54 ±
0.33 P=
0.132
0.13 ± 0.09
P= 0.234
0.02 ± 0.02
P= 0.004
Table 3. Allotment soil competition sample analysis of mean ± SD and (Shapiro-Wilks) normality (P) per sample
plant species

6. Table 4. Contaminatedsoil competition sample analysisof mean ± SD and (Shapiro-Wilks) normality (P) per sample
plant species
Comparisons between table 1 and table 3 demonstrate that in both T.pratense and L.perenne
there is a notable increase in biomass with L.perenne almost doubling in total fresh weight
when planted in competition with the two other plant species. F. ovina however demonstrated
notable decline in biomass between table 1 and table 3, indicating reduction in productivity
when planted with the two other plant species. The shoot to root ratio of L.perenne
demonstrated a notable increase in root production within the allotment competition pots. F.
ovina indicated a reduction in root production within competition pots in comparison to root
production in the control pot.
Comparatively, table 2 and table 4 demonstrate an increase in biomass production between
T.pratense and L.perenne with the highest amount of biomass recorded in the competition
pots. However even in contaminated soil F. ovina demonstrates decline in biomass
production when placed in competition pots.
T.pratense has P value of 0.531 when a Mann-Whitney U test is performed indicating that
null hypothesis that “soil type does not influence self/non-self discrimination” should be
accepted and there is no difference in self/non-self discrimination between soil types for this
species.
L.perenne has a P value of 0.664 when a Mann-Whitney U test is performed indicating that
null hypothesis that “soil type does not influence self/non-self discrimination” should be
ContaminatedCompetition
Plantvariable T.pratense L. perenne F. ovina
ShootFreshwt (g)
2.31 ± 0.83
P= 0.081
0.65 ± 0.49
P= 0.210
0.07 ± 0.06
P= 0.144
Root Fresh(g)
1.14 ± 0.54
P= 0.019
0.83 ± 0.81
P= 0.024
0.08 ± 0.12
P= 0.000
Total PlantFreshwt(g)
3.44 ± 1.13
P= 0.001
1.48 ± 1.19
P= 0.218
0.16 ± 0.15
P=0.031
ShootDry wt (g)
0.28 ± 0.14
P= 0.029
0.10 ± 0.11
P= 0.053
0.01 ± 0.01
P= 0.008
Root Dry wt (g)
0.11 ± 0.20
P= 0.000
0.05 ± 0.05
P= 0.026
0.06 ± 0.05
P= 0.048
Total PlantDry wt(g)
0.41 ± 0.18
P= 0.428
0.15 ± 0.12
P= 0.008
0.07 ± 0.51
P= 0.044

7. accepted and there is no difference in self/non-self discrimination between soil types for this
species.
F. ovina has a P value of 0.130 when a Mann-Whitney U test is performed indicating that
null hypothesis that “soil type does not influence self/non-self discrimination” should be
rejected and there is a difference in self/non-self discrimination between soil types for this
species.
AllotmentControl
Plantvariable No Plants T.pratense L. perenne F. ovina
Soil Microbial FDA hydrolysisactivity
(µg fluoresceing-130 min-1)
0.29 ± 0.35
P= 0.084
0.36 ± 0.46
P= 0.167
0.54 ± 0.58
P= 0.109
1.11 ± 1.00
P= 0.498
Table 5. FDA hydrolysis of soil microbial activity in allotment soil control sample analysis of mean ± SD and
(Shapiro-Wilks) normality (P) per sample plant species and non-planted soil
ContaminatedControl
Plantvariable No Plants T.pratense L. perenne F. ovina
Soil Microbial FDA hydrolysisactivity
(µg fluoresceing-130 min-1)
0.21 ± 0.15
P= 0.079
0.61 ± 0.94
P= 0.002
0.55 ± 0.36
P= 0.725
0.14 ± 0.11
P= 0.076
Table 6. FDA hydrolysis of soil microbial activity in contaminated soil control sample analysis of mean ± SD and
(Shapiro-Wilks) normality (P) per sample plant species and non-planted soil
AllotmentCompetition
Plantvariable All Plants
Soil Microbial FDA hydrolysisactivity
(µg fluoresceing-130 min-1)
0.68 ± 0.77
P= 0.008
ContaminatedCompetition
Plantvariable All Plants
Soil Microbial FDA hydrolysisactivity
(µg fluoresceing-130 min-1)
0.40 ± 0.22
P= 0.189
Table 7. FDA hydrolysis of soil microbial activity in contaminated and allotment soil competition sample analysis of
mean ± SD and (Shapiro-Wilks) normality (P) for all plants
A Kruskal-Wallis test was performed on the data from table 5 and found that there was no
significant difference between planted and non-planted allotment pots, per species; producing
a P value of 0.389 concluding that the null hypothesis that there is a difference between in
microbial activity in planted and non-planted soil, should be rejected.

8. Another Kruskal-Wallis test was run on the table 6 data and the same conclusions were found
in contaminated soil with a P value of 0.174 and rejecting the same null hypothesis.
A Mann-Whitney U test was then performed on the table 7 data and soil type did not produce
any significant difference in microbial activity, producing a P value of 0.962 and rejecting the
null hypothesis that microbial activity is different per soil type.
Discussion
The findings from this study cannot extensively test the aims of the investigation due to the
high volume of standard error in the data collect and the large degree of operator and
instrumental error. Comparatively to previous attempts at this investigation, previous datasets
was substantially more comprehensive and more substantial in quantity than the dataset used
in this study. Subsequently operator error in the handling and preparation of the specimens
for testing, had a greater impact on the data analysis as the resulting dataset means were
notably skewed and the standard deviation per data variable significantly fluctuated due to
the high amount of standard error.
The findings from this study would indicate that the contaminates in the contaminated soil
had no impact on plant growth production, root growth or soil microbial activity. This is in
direct contradiction to findings observed by Kim et al (2012) who found the presence of Pb
changed microbial activity and Lin et al (2014) who found Cu and Pb impact on root growth
and metal uptake in plants.
With regards to self/non-self discrimination, mild differences per species between the two
soil types could be observed in root growth. In both soil type T.pratense had the greater
biomass and could be considered the dominant species, with L.perenne indicating mild
competition root growth in the allotment soil; however statistical analysis of this data
determined the growth was not significant enough to support self/non-self discrimination. F.
ovina continued to be relatively indifferent in both soil type and treatment, consistently
producing the lowest biomass and failing to support any hypothesis. This directly contradicts
findings that F. ovina can survive in soils low in nutrients and has notable symbiotic relations
with mycorrhizal fungi which aids the plants establishment by extracting minerals,
phosphates and nitrogen (Granath et al 2007). This could indicate that the presence of the two
other plant species could have impacted on the growth production of F. ovina and caused the

9. consistently poor biomass production, however this would require further testing to
determine.
Overall the findings from this study are inconclusive due to a same dataset and high amount
of operator error. Weights produced by some operators were clearly taken incorrectly and
preparation of the specimens for testing was not consistent throughout all operators taking
place in the study. Future improvements to this study could be the standardisation of
specimen preparation by a single operator to ensure greater control over all measured
variables. In addition to this, a larger dataset to provide more validity to the statistical
analysis is required. Potentially the production of more specimens/pots, produced over a
greater length of time could be of benefit to the test species to allow for greater opportunity
for self/non-self below ground competition to be established.

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