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Content uploaded by Lawrence Kasaga
Author content
All content in this area was uploaded by Lawrence Kasaga on Mar 29, 2022
Content may be subject to copyright.
MAKERERE UNIVERSITY
COLLEGE OF NATURAL SCIENCES
DEPARTMENT OF PLANT SCIENCES, MICROBIOLOGY AND BIOTECHNOLOGY
IMPACT OF Lantana camara ON NATIVE VEGETATION STRUCTURE AND
DIVERSITY OF KAKIIKA, MBARARA, UGANDA.
BY
LAWRENCE KASAGA
Reg No.: 18/U/9438/PS
Student No.: 1800709438
PROJECT SUPERVISOR
POFESSOR JAMES KALEMA
A RESEARCH REPORT SUBMITTED TO THE DEPARTMENT OF PLANT SCIENCES,
MICROBIOLOGY AND BIOTECHNOLOGY AS PARTIAL FULFIMNET OF THE
REQUIREMNTS FOR THE AWARD OF THE DEGREE OF BACHELOR OF SCIENCE
IN CONSERVATION BIOLOGY AT MAKERERE UNIVERSITY
Department of plant sciences, microbiology and biotechnology
School of Biosciences
College of Natural Sciences
Makerere University
January, 2022
i
DECLARATION
By submitting this thesis, I declare that the entirety of the work contained herein is my own,
original work, that I am the sole author thereof (save to the extent explicitly otherwise stated),
that reproduction and publication thereof by Makerere University will not infringe any third-
party rights and that I have not previously in its entirety or in part submitted it for obtaining
any qualification.
Signature:
Lawrence Kasaga
ii
Approval
This research report has been submitted for examination with approval of my supervisor.
Signature Date: 22 March 2022
James Kalema (PhD)
Professor of Botany,
College of Natural Sciences
Makerere University
iii
Abstract
Lantana camara has been spreading in Kakiika with little assessment and control which was
posing threat to the area’s biodiversity. Using transects and plot sampling techniques, the
impact of this notorious weed on the species diversity and structure was established. The
invasive plant was found to cause adverse effects mostly on graminoid species and most non-
woody plant species where it may result into suppression of various native plant species of
invaded communities. The general plant species diversity, density, richness and cover were
reduced by the invasion of Lantana camara. Kyllinga alba and Digitarlia ciliaris are some of
the grass species that thrive under Lantana camara thickets at very low sunlight light
penetration. Lantana camara reduced the plant species densities, diversity, richness and cover
of the invaded communities with an exception of climbers where their richness, diversity and
cover were higher in the invaded communities. Therefore, sustainable control measures should
be taken to eliminate and stop the spread of the invasive Lantana camara.
iv
Acknowledgement
With great thanks I honour the great contribution to all groups and individuals who put in
their effort to the success of this research project especially Professor. James Kalema; the
project supervisor, the team of Makerere University Herbarium led by Dr. Mary Namaganda
for the effort put in identifying herbarium specimens, dad, mom and siblings, Mr. Hilary
Ssuna and Miss Christine Nassali for the financial assistance given and Joseph Clever
Ddembe Ainebyoona for the field assistance he offered. The named individuals did the
utmost contribution to the achievement and the success of this research project without whom
it would have been difficult to accomplish.
This report is further dedicated to Walkers, Swifties, Illenials and the EDM fraternity for
unconditional love, endless entertainment and linking art with environmental protection.
v
Table of Contents
1 Introduction ......................................................................................................................... 1
1.1 Background ................................................................................................................. 1
1.2 Problem statement ....................................................................................................... 1
1.3 1.3.0 Objectives ........................................................................................................... 2
1.3.1 General objective ................................................................................................. 2
1.3.2 Specific objectives ............................................................................................... 2
1.4 Hypotheses .................................................................................................................. 2
1.5 Significance of the study ............................................................................................. 2
1.6 Justification ................................................................................................................. 2
2 Literature review ................................................................................................................. 3
2.1 General description and general ecology of Lantana camara ..................................... 3
2.2 Distribution and factors that favour Lantana camara as an invasive species ............. 4
2.3 Impacts of lantana camara on terrestrial ecosystems ................................................. 5
2.4 Effects on fauna ........................................................................................................... 5
3 Data collection methods and materials ............................................................................... 6
3.1 Study area .................................................................................................................... 6
3.1.1 Climate ................................................................................................................. 6
3.1.2 Vegetation ............................................................................................................ 7
3.2 Sampling strategy ........................................................................................................ 7
3.3 Woody vegetation attributes........................................................................................ 7
3.4 Non-woody vegetation attributes ................................................................................ 8
3.5 Data analysis methods ................................................................................................. 8
vi
3.5.1 Plant species diversity of invaded and uninvaded communities .......................... 8
3.5.2 Level of similarity between invaded and uninvaded vegetation communities .... 8
3.5.3 Density of species ................................................................................................ 9
3.5.4 Plant species cover ............................................................................................... 9
3.5.5 Significance in plant species abundance, density and cover ................................ 9
4 Results ............................................................................................................................... 10
4.1 Species richness......................................................................................................... 10
4.1.1 Comparison of species richness of different growth habits in the invaded and
uninvaded vegetation communities................................................................................... 11
4.2 Plant species abundance ............................................................................................ 13
4.2.1 Plant species abundance of the growth habits.................................................... 13
4.3 Level of similarity between the invaded and uninvaded vegetation communities ... 14
4.4 Plant species density.................................................................................................. 14
4.5 Plant species percentage cover .................................................................................. 17
4.6 Species diversity of the invaded and uninvaded vegetation communities ................ 18
5 Discussion ......................................................................................................................... 18
5.1 Introduction ............................................................................................................... 18
5.2 Effect of Lantana camara on plant species richness, abundance, diversity and
structure of the invaded and uninvaded vegetation communities ........................................ 19
5.2.1 Effect of Lantana camara on plants species richness and abundance ............... 19
5.2.2 Effect of Lantana camara on plant species diversity ........................................ 20
5.2.3 Effect of Lantana camara on plant species density ........................................... 20
5.3 Level of similarity between invaded and uninvaded vegetation communities. ........ 21
5.4 Impact of Lantana camara invasion on plant species cover ..................................... 21
vii
6 Conclusion and recommendations .................................................................................... 22
6.1 Conclusion ................................................................................................................. 22
6.2 Recommendations ..................................................................................................... 22
7 References ......................................................................................................................... 23
viii
List of figures
Figure 1: Species richness of the different growth habits of invaded and uninvaded
communities of Nyakabungo village. ...................................................................................... 11
Figure 2: Species richness of different growth habits in invaded and uninvaded communities
of Nyakabungo village. ............................................................................................................ 11
Figure 3: Species richness of different growth habits in invaded and uninvaded vegetation
communities of Butagatsi village............................................................................................. 12
Figure 4: Plant species abundance of the invaded and uninvaded vegetation communities. .. 13
Figure 5: Plant species abundance of trees, climbers and forbs in invaded and uninvaded
communities. ............................................................................................................................ 13
Figure 6: Plant species abundance of forbs and graminoids in invaded and uninvaded
communities. ............................................................................................................................ 14
Figure 7: Mean species density of trees in the invaded and uninvaded vegetation
communities. ............................................................................................................................ 15
Figure 8: Mean species density of shrubs in the invaded and uninvaded vegetation
communities. ............................................................................................................................ 15
Figure 9: Mean species density of forbs in the invaded and uninvaded vegetation
communities. ............................................................................................................................ 16
Figure 10: Mean species density of climbers in the invaded and uninvaded vegetation
communities. ............................................................................................................................ 16
Figure 11: Mean species density of graminoids in the invaded and uninvaded vegetation
communities. ............................................................................................................................ 17
Figure 12: Mean species percentage cover of the growth habits in the invaded and uninvaded
vegetation communities. .......................................................................................................... 17
Figure 13: The Shannon’s diversity index values and abundance of the invaded and
uninvaded vegetation communities.......................................................................................... 18
List of tables
Table 1: Comparison of species richness between the invaded and uninvaded vegetation
communities. ............................................................................................................................ 10
1
1 Introduction
1.1 Background
Lantana camara is a small perennial shrub which can grow to about 2m tall and forms dense
thickets in a variety of environments (Arne, et al., 2018). It is native plant of South and
Central America. Lantana camara is classified amongst world’s ten worst weeds and is
reported to have invaded millions of hectares of natural and cultivated lands, causing great
ecological and socio-economic damage. (Qin, et al., 2015). Moreover, the high adaptability of
this species to a wide range of climatic conditions has also allowed it to thrive in diverse
habitats such as riverbanks, mountain slopes, valleys, pastures, and commercial forests where
it forms impenetrable stands that obstruct access and use (Sharma, et al., 2005).Other impacts
might include low animal quality, reduced crop yields and reduced functioning of natural and
semi-natural ecosystems as it forms dense thickets that supress or prevent other plants from
growing.
In Uganda, Lantana camara is termed as an alien invasive plant species. It was introduced in
the 1960’s and has since then became a notorious weed commonly in savannah systems such
as Lake Mburo National Park (Kiwuso, et al., s.d). In Kakiika rangelands, Lantana camara
has been observed and thought to have led to reduced forage available for livestock.
1.2 Problem statement
Lantana camara has been observed to have spread all over Kakiika Sub County but it is still
not assessed to establish its impact on the terrestrial environment. The invasive plant
continues to propagate and spread in crop fields, grazing areas and natural ecosystems with
very little control which might cause drastic reduction of the aboveground biomass by
suppressing native plant species. This could lead to food insecurity and loses in farming
systems, hence slowing down economic growth and development. This study therefore aims
at understanding how Lantana camara invasion impacts the native plant species structure and
diversity, whose findings will form a basis of devising means of controlling and mitigating
the effects brought about by the invasion of Lantana camara.
2
1.3 1.3.0 Objectives
1.3.1 General objective
To assess impact of Lantana camara on native vegetation.
1.3.2 Specific objectives
i) To compare native plant species richness, diversity and structure between Lantana
camara invaded and uninvaded plant communities.
ii) To assess the effect of Lantana camara invasion on cover of native plant
communities.
1.4 Hypotheses
Ho: There is no significant difference in plant species richness, structure and diversity
between Lantana camara invaded and uninvaded plant communities.
Ho: There is no significant impact of Lantana camara invasion on the cover of plant
species.
1.5 Significance of the study
Establishing the variations of native plant species diversity and richness between Lantana
camara invaded and Lantana camara free plant communities will play a great role in the
future planning and management of the rangelands. From the information available from the
previous studies, Lantana camara causes change in ecological succession and alters the plant
composition at climax. Therefore, results from this study will point out the extent of damage
Lantana camara imposes on native plant species thus this will form the baseline for the
formulation of appropriate management plans and policies on how to fight Lantana camara
and improve forage available for animals which will increase the production of the
rangelands.
1.6 Justification
The impact of Lantana camara on the rangelands is observed in causing suppression of many
plant species. This study is required to establish the variations brought about by the invasion
3
of Lantana camara so as to establish the extent of damage and find out mitigation and
preventive measures basing on the results of this study.
2 Literature review
2.1 General description and general ecology of Lantana camara
Classification
Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Order: Lamiales
Family: Verbenaceae
Genus: Lantana
Species: camara
Scientific name: Lantana camara
Lantana camara belongs to the family verbanaceae characterised with thorny stems and
serrated leaf margins with a network venation (Bharath, et al., 2012), with commonly purple,
red and yellow flowers (Orjan, et al., 2005). It produces a poisonous powder, allelochemicals
thus suppresses most of the plants where it grows (Om, et al., 2007). Lantana camara is
named under the ten world’s worst weeds. The plant has spread across tropical and
subtropical Africa, Asia and Australia in about 60 countries where it was introduced as a
garden ornamental or hedge plant (Ross, et al., 2017) Lantana camara invades in any plant
community brings about various changes these which are both biotic and abiotic (Olusegun,
et al., 2010). Abiotic alterations are mostly concerned with changes in edaphic chemical
properties, soil structure, texture, soil infiltration rates and aeration (Day, et al., 2003). Biotic
changes are commonly seen in altered succession regimes, which leads to community
composition changes at climax, suppression of other plants leading to composition changes
4
and modifying the structure of the plant community regarding native spatial and temporal
distribution, age structure and species richness and diversity (Walton, 2006). All these
changes lead to the variations in species diversity and composition that occur between the
invaded and the free plant communities, and these variations means shifts in the functioning
of an ecosystem. In severe Latana camara invasions, ecological systems suffer severe
damages which are hard to reverse even after the removal of the invader.
2.2 Distribution and factors that favour Lantana camara as an invasive species
Latana camara grows well in areas located between 350N and 250S and these are tropical and
sub-tropical regions. As approaching the Equator, conditions become more favourable for
Lantana camara since there is more precipitation and small diurnal temperature range which
favour its growth (Swarbrick, et al., 1998). It is a native plant of South and Central America
(Qin, et al., 2015). The plant has spread across tropical and subtropical Africa, Asia and
Australia in about 60 countries where it was introduced as a garden ornamental or hedge
plant (Ross, et al., 2017). In Uganda, Lantana camara is a weed commonly in savannah
systems such as Lake Mburo National Park. However, most cases of Latana camara invasion
have been reported in almost every part of the country except on tall mountains and in aquatic
habitats.
Lantana camara is favoured by a range of factors, climate being the main; others are
topography, land use and land cover (Arne, et al., 2018). Land degradation or disturbances
such as over grazing are the major drivers of Lantana invasion. Practices such as slash and
burn agriculture, timber and charcoal extraction, deforestation, overgrazing, cultivation on
steep slopes, uncontrolled fires and pollution together favour the growth of Lantana camara
over other plant species (Arne, et al., 2018). This plant grows in areas with high precipitation
and can thrive even in semi-arid areas. However, Lantana camara is not favoured by extreme
cold conditions. Lantana camara establishes itself very fast in tropical forests in case of a
disturbance that creates a forest gap though forested area. Intact tropical forests have been
thought to inhibit the growth of Lantana camara as it requires much light to develop. In
savannahs, Lantana camara easily colonises very fast especially when herbivory and fires are
at their peak since it is less affected by these disturbances.
Human-made and natural disturbances act together to help the introduction and spread of
Lantana camara (Firew, 2018). The various colours of Lantana camara flowers helps it to be
cultivated for its ornamental purpose and its utilization for fencing facilitate its dispersal.
5
Lantana camara biological attributes like high number of production of fruits each year
(prolific seed production) and duration of fruit production (which is throughout the year when
conditions are favourable such as adequate light and moisture) (Orjan, et al., 2005), its ability
to propagate vegetative by a process called layering where horizontal stems take root when
they are in contact with moist soil, ability of the weed seeds to germinate at any time of the
year and the seed viability for longer periods ranging from 2-5 years, better competitive
ability compared to native flora, and widespread geographic range (wide ecological
tolerance) (Om, et al., 2007) contribute to the success of its dispersal and growth. In addition
to its biological attributes, the quick spread of its fruit by birds (which are predominant
dispersers) (Swarbric, et al., 1995) and animals that eat its fruits (Tamiru, 2017) may have
accelerated its dispersal.
2.3 Impacts of lantana camara on terrestrial ecosystems
Lantana camara has the potential of blocking succession and causes displacement of native
plant species which leads to biodiversity loss (Chrispine, et al., 2008). It causes striking
changes in structural and floristic composition of natural communities by interrupting the
regeneration process of other native plant species thus reducing species richness. (Kiwuso, et
al., s.d), Found out that Lantana camara reduces native species diversity and declines the soil
fertility. Also (Gooden, et al., 2009) described it to cause allelopathic alterations of soil
properties. Furthermore, it alters eco system processes such as nutrient cycling (Orjan, et al.,
2005) Some plant species are supressed by Lantana camara as it produces toxic
allelochemicals as discussed by (Arne, et al, 2018) and (Ross, et al., 2017) stated that also
suppression is by forming dense thickets that block other plants from sunlight.
2.4 Effects on fauna
Lantana camara is known to produce secondary compounds, which have been implicated in
ungulate poisoning where ingestion of Lantana camara by grazing animals causes cholestasis
and hepatoxicity (Tamiru, 2017). Lantana camara contain triterpenoids, which cause death
through poisoning and photosensitivity (Bharath, et al., 2012). The replacement of native
vegetation by Lantana camara thickets reduces the amount of available forage and habitat for
native animals which reduces the carrying capacity of the Lantana camara infested area
(Mwoleka, 2019).
6
3 Data collection methods and materials
3.1 Study area
The study was conducted in Kakiika Nyakiziba, Nyakabungo and Butagatsi, which lie in the
Northern part of Mbarara City, South Western Uganda. The main economic activity is cattle
ranching with vast land under this activity. Cultivation is done to a small extent with banana
and coffee plantations being the dominant crops. Other crops include; legumes, cereals and
commercial trees. The common methods of agriculture are free ranging for livestock and also
paddocking, shifting cultivation is done to a small extent and crop rotation done often with
farrow periods at certain intervals of the year. Fertilizer application is limited. The area has
large numbers of livestock which are mostly free ranging with few isolated paddocks. The
land tenure system is mostly communal and free hold and there is less vegetation clearance in
the livestock farms thus the Lantana camara shrub has established a climax state of between
4-6 years. The area has good road networks which made movements easy and has friendly
communities which minimised conflict during data collection.
Kakiika division has an average elevation of1,438 meters (The Republic of Uganda, 2010). It
borders with Kakoba Division and Kamukuzi Division in the south, Biharwe Division in the
west, Rubaya and Rwanyamahembe Subcounties of Mbarara District in the North, Bubaare
Subcounty of Mbarara District in the West and Nyakayojo Division in the South West (The
Republic of Uganda, 2010).
Map of Uganda indicating the location of Kakiika
3.1.1 Climate
The area receives 990 mm to 1000 mm of rainfall per annum. Temperature ranges between
16oC and 31oC and humidity of 60% to 80% (The Republic of Uganda, 2010).
7
3.1.2 Vegetation
The area has a savanna grassland interspersed with shrubs, bushes and wooded grasslands.
Grasslands cover the largest area with Brachialis decumbens and Sporobolus pyramidalis
being the dominant grass species. The wooded grasslands are dorminated by accacia species
as the major trees and shrubs. (Landale-Brown, et al., 1964). Other dorminat species of forbs
and climbers were Justicia exigua and Ipomea purpurea respectively.
3.2 Sampling strategy
The line transects and plot sampling technique was used as described by (Sumia, et al., 2017).
Data was collected in three invaded and three uninvaded plant communities in three adjacent
pairs of one invaded and one uninvaded community to minimise the physic-chemical
environmental factor variations between the communities. The plots were set at a minimum
of 50 m from the main roads to minimize the edge effect. Ten large plots of 20 m x 20 m for
sampling trees were set along a line transect of 400 m in each selected community with a plot
to plot interval of 20 m. Medium plots of 10 m x 10 m were set within the large 20 m x 20 m
plots for sampling shrubs and large herbaceous plants, and 1 m x 1 m plots were set within
the large plots for sampling small herbaceous plants and graminoids.
Data regarding the canopy cover of Lantana camara in the invaded communities was
estimated (Matthew, et al., 1993) and recorded per plot as a percentage (%). Lanta camara
cover of the uninvaded communities was taken to be zero percent (0%). Data samples were
collected from the set plots in both Lantana camara invaded and no-invaded plant
communities. Individual plant species occurring in each plot was identified on communities
and those difficult to identify were collected and placed on herbarium boards and transferred
to Makerere herbarium for identification. the identified plant species were groups in four
categories; trees, shrubs, forbs and graminoids. The above ground percentage cover for the
identified plant species per plot was recorded in a table.
3.3 Woody vegetation attributes
Species richness was determined by recording the number of the different species contained
in each plot, and the number of individuals of each species, was also recorded for assessing
species composition. Crown diameter of trees and shrubs was used to estimate their cover.
Two greatest crown diameters (D1 & D2) of each woody plant, perpendicular to each other
8
were measured and averaged to get the mean diameter (D). Then mean diameter was used to
estimate the crown cover from; Crown cover=π (D/2) ², where D is the mean crown diameter
(Mwoleka, 2019).
3.4 Non-woody vegetation attributes
Species richness was determined by recording the number of species in each plot, and the
number of individuals of each species were recorded for assessing species composition. The
area occupied by a single plant within the plot was measured and used to estimate percentage
cover, and this was done for all plants of the same species in the plot and their total cover was
determined. The overall community’s plant species percentage cover was obtained as an
average of percentage cover of all plots per species.
3.5 Data analysis methods
3.5.1 Plant species richness and abundance
The species richness of every village was determined by counting the number of species
contained in all plots of both the invaded and uninvaded plant communities and grouped
according to the growth habit. (Mwoleka, 2019). The abundance of species was obtained by
counting the individuals per species in every plot and their sum of all plots in each village
was established.
3.5.2 Plant species diversity of invaded and uninvaded vegetation communities
The species diversity of the three villages of the invaded and uninvaded plant communities
shall be determined using the Shannon index of diversity (Magurran, 2004)from the formula;
Where pi is the proportion of species i and In is the natural logarithm
3.5.3 Level of similarity between invaded and uninvaded vegetation communities
The Jacquard coefficient of similarity was used to compare the invaded with then uninvaded
plant communities as it was used by (Yuvenalis , et al., 2020) to compare two different plant
communities. The result of this formula provided a basis of drawing inference that the
invaded and uninvaded communities are either similar or dissimilar (Parveen, et al., 2011).
9
Jacquard coefficient of similarity; CCj =
Where; C: Species in common
S1: Species in Lantana camara invaded communities
S2: Species in Lanta camara free communities.
3.5.4 Density of species
The density of individual species per vegetation communities was determined and used to
obtain the mean density of the growth habits per village.
Density, D
Where N: total number of individuals.
A: The total area worked in.
Then mean density was calculated from;
Mean density
Where ∑D: sum of individual species density
n: species richness of the communities
3.5.5 Plant species cover
The percentage cover per species was determined using the percentage cover formula and the
mean percentage cover of all species per village was calculated and noted.
Percentage cover (%), A ═
Mean percentage cover
3.5.6 Significance in plant species abundance, density and cover
The Student’s t-test for independent sample data was used to test for the significance of the
differences in species abundance, density and percentage cover between the invaded and
10
uninvaded communities. Data of abundance and percentage cover was transformed using
log10 so as allow the applicability of the Student’s t-test for independent samples.
4 Results
4.1 Plant species richness
The species richness of every village was determined by summing up the number of species
contained in all plots of both the invaded and uninvaded plant communities. The recorded
species were grouped in five, thus of trees, shrubs, forbs, climbers and graminoids. 120
species were recorded where L. camara invaded plant communities had fewer native plant
species compared to uninvaded plant communities. From a total number of 120 species
recorded, more species were recorded in the uninvaded communities than in invaded
communities as shown in (table 1)
Table 1: Comparison of species richness between the invaded and uninvaded vegetation
communities.
Village
Plant community
Only
invaded
Only
uninvaded
Both invaded
and uninvaded
Total
Nyakabungo
Species richness
16
40
18
74
Nyakiziba
Species richness
13
44
28
85
Butagatsi
Species richness
11
52
22
85
11
4.1.1 Comparison of species richness of different growth habits in the invaded and
uninvaded vegetation communities.
Figure 1: Species richness of the different growth habits of invaded and uninvaded
communities of Nyakabungo village.
From (figure 1) above, there were no graminoids recorded only in the invaded community
and also no climbers were recorded only in the uninvaded community.
Figure 2: Species richness of different growth habits in invaded and uninvaded communities
of Nyakabungo village.
0
2
4
6
8
10
12
14
Only invaded Only uninvaded Both invaded and uninvaded
Species richness
Vegetation community
Species richness of different growth habits in the invaded and
uninvaded vegetation communities in Nyakabungo village
Trees Shrubs Forbs Climbers Graminoids
0
2
4
6
8
10
12
14
16
18
Only invaded Only uninvaded Both invaded and uninvaded
Number of species
Vegetation community
Species richness of different growth habits in the invaded and
uninvaded vegetation communities in Nyakiziba village
Trees Shrubs Forbs Climbers Graminoids
12
There were no graminoids recorded only in the invaded community as illustrated in (figure 2)
above. The uninvaded community had more trees, shrubs and forbs than the invaded
community. The invaded community however, had more climbers than the uninvaded
community.
Figure 3: Species richness of different growth habits in invaded and uninvaded vegetation
communities of Butagatsi village.
The uninvaded community had more species of trees, shrubs, forbs and graminoids well as
the invaded community had more species of climbers.
0
2
4
6
8
10
12
14
16
18
20
Only invaded Only uninvaded Both invaded and uninvaded
Number of species
Vegetation community
Species richness of different growth habits in the invaded and
uninvaded vegetation communities in Butagatsi village
Trees Shrubs Forbs Climbers Graminoids
13
4.2 Plant species abundance
Figure 4: Plant species abundance of the invaded and uninvaded vegetation communities.
From (figure 4) above, the plant species abundance was significantly higher in the uninvaded
communities than in invaded communities of Nyakabungo (t=3.214, p<0.01, n=113),
Nyakiziba (t=4.021, p<0.01, n=112) and Butagatsi (t=3.546, p<0.01, n=109).
4.2.1 Plant species abundance of the growth habits
Figure 5: Plant species abundance of trees, climbers and forbs in invaded and uninvaded
communities.
0
500
1000
1500
2000
Nyakabungo Nyakiziba Butagatsi
Total number of species, N
Village
Plant species abandance of the invaded and
uninvaded vegetation communities
Invaded Uninvaded
0
100
200
300
400
500
600
Nyakabungo Nyakiziba Butagatsi
Total number of individuals, N
Village
Species abundance of trees, shrubs and
climbers
Trees-IN Trees-UN Shrubs-IN Shrubs-UN Climbers-IN Climbers-UN
Key
IN: invaded
community
UN: uninvaded
community
14
Figure 6: Plant species abundance of forbs and graminoids in invaded and uninvaded
communities.
4.3 Level of similarity between the invaded and uninvaded vegetation communities
The Jacquard index of similarity between the invaded and uninvaded vegetation communities
was found the be 0.318, 0.302 and 0.253 in Nyakabungo, Nyakiziba and Butagatsi
respectively, of which all were below the 0.5 minimum threshold for similar communities
hence were dissimilar.
4.4 Plant species density.
The uninvaded communities had higher mean plant densities than the invaded communities
with an exception of the climbers where the mean densities in the invaded communities were
higher than those of uninvaded communities. The graminoids had the highest mean density
per hectare in both the invaded and uninvaded communities.
The plant species density of was significantly higher in uninvaded communities than in
invaded communities of Nyakabungo (t=3.432, p<0.01, n=113), Nyakiziba (t=3.533, p<0.01,
n=112) and Butagatsi (t=4,17, p<0.01, n=109).
0
200
400
600
800
1000
1200
Nyakabungo Nyakiziba Butagatsi
Total number of individuals, N
Village
Species abundance of forbs and graminoids
Forbs-IN Forbs-UN Graminoids-IN Graminoids-UN
Key
IN: invaded
community
UN: uninvaded
community
15
Figure 7: Mean species density of trees in the invaded and uninvaded vegetation
communities.
The mean species densities of trees as shown in figure (1) above were high in uninvaded
communities than invaded communities, however the difference between these mean species
densities is small indicating a slight variation.
Figure 8: Mean species density of shrubs in the invaded and uninvaded vegetation
communities.
0
2
4
6
8
10
12
14
Nyakabungo Nyakiziba Butagatsi
Mean density
(individuals/species/hactare)
Villages
Mean species density of trees
Invaded Uninvaded
0
50
100
150
200
250
Nyakabungo Nyakiziba Butagatsi
Mean density
(individuals/species/hactare)
Villages
Mean species density of shrubs
Invaded Uninvaded
16
Figure 9: Mean species density of forbs in the invaded and uninvaded vegetation
communities.
Figure 10: Mean species density of climbers in the invaded and uninvaded vegetation
communities.
0
2000
4000
6000
8000
10000
12000
Nyakabungo Nyakiziba Butagatsi
Mean density
(individuals/species/hactare)
Villages
Mean species density of forbs
Invaded Uninvaded
0
20
40
60
80
100
120
Nyakabungo Nyakiziba Butagatsi
Mean density
(individuals/species/hactare)
Villages
Mean species density of climbers
Invaded Uninvaded
17
The invaded communities had higher mean species densities of climbers than uninvaded
communities as illustrated in figure (4) above.
Figure 11: Mean species density of graminoids in the invaded and uninvaded vegetation
communities.
4.5 Plant species percentage cover
Butagatsi village had the highest Lantana camara invasion with an average percentage cover
of 99.6% followed by Nyakiziba with 98.3% and lastly Nyakabungo with 93.9% cover of
Lantana camara.
Figure 12: Mean species percentage cover of the growth habits in the invaded and uninvaded
vegetation communities.
0
20000
40000
60000
80000
100000
Nyakabungo Nyakiziba Butagatsi
Mean density
(individuals/species/hectare)
Villages
Mean species density of graminoids
Invaded Uninvaded
0
5
10
15
20
25
30
35
40
Nyakabungo Nyakiziba Butagatsi
Mean species percentage cover (%/species)
Villages
Mean plant species percentage cover of growth habits
Trees-IN Trees-UN Shrubs-IN Shrubs-UN Forbs-IN
Forbs-UN Climbers-IN Climbers-UN Graminoids-IN Graminoids-UN
Key
IN: invaded
community
UN: uninvaded
community
18
The plant species percentage cover as indicated in figure (6) above was determined as mean
of percentage cover of all species per growth habit per vegetation communities. The
uninvaded communities in general had significant higher plant species cover of native plant
species than the invaded communities of Nyakabungo (t=4.20, p<0.01, n=113), Nyakiziba
(t=3.982, p<0.01, n=112) and Butagatsi (t=4.112, p<0.01, n=109). This was due to the fact
that in the invaded communities, Lantana camara occupied the largest space forming huge
canopy cover that prevented most of other plants from growing but rather favoured the
growth of climbers. In the invaded communities, the overall average percentage cover of
graminoids was 6.67% too low when compared to 29.03% of the uninvaded vegetation
communities.
4.6 Species diversity of the invaded and uninvaded vegetation communities
Figure 13: The Shannon’s diversity index values and abundance of the invaded and
uninvaded vegetation communities.
The uninvaded communities had higher diversity of species than the invaded communities as
illustrated in figure (7) above. The higher species diversity in the uninvaded communities was
due to the fact that these communities had higher species abundances than the invaded
communities.
5 Discussion
5.1 Introduction
The high Lantana camara percentage cover in the invaded vegetation communities caused
drastic reduction in the cover of various native plant species of which the most affected were
2.6
2.8
3
3.2
3.4
3.6
Nyakabungo Nyakiziba Butagatsi
Shannon's index, H
Villages
Shannon's index of the invaded and uninvaded
vegetation communities
Invaded community Uninvaded community
19
graminoids, followed by forbs, climbers, shrubs, and then trees. At an overall average cover
of 97.27%, L. camara, imposed major impact on the graminoids and forbs same as the results
obtained by (Martin, 2014) at Imire ranch, Wedza district, Zimbabwe. Martin observed a
general decrease of herbeceous species abandance and diversity in the invaded communities.
Low biodiversity recorded in the invaded communities could be attributed to the fact that L.
camara produces and releases phenolic acids, flavonoids, terpenes and terpenoids, which are
known to inhibit the growth of other plants and impede growth of plants growing close
(Martin, 2014).
5.2 Effect of Lantana camara on plant species richness, abundance, diversity and
structure of the invaded and uninvaded vegetation communities
5.2.1 Effect of Lantana camara on plants species richness and abundance
The uninvaded communities had high species richness and diversity compared to the invaded
communities. The species richness between the invaded and uninvaded communities had a
great variation where the uninvaded communities were richer than the invaded communities
similar to that obtained by (Ashok & Anup, 2017). Woody plants that’s is most trees and
shrubs were less affected. The most affected plants were graminoids, climbers and forbs.
Digitarlia ciliaris, Kyllinga alba and Panicum maximum were the only graminoids to have
been found growing under Lantana camara thickets in dwindling populations at very low
light penetration. On the side of forbs, only Commelina bengalinesis was found to thrive in
very small populations that survive under very low light penetration similar to findings of
(Ytagesu & Denjene, s.d). establishing that; no grass species and forbs herbaceous plants.
95% cover and above of L. camara, no forbs and graminoids survive. This indicated that the
invasion of Lantana camara had a capability of causing suppression of various intolerant
plant species especially graminoids and forbs.
Similarly, (Harminder, et al., 2014) found out that Lantana camara invasion reduced
diversity of vegetation by chemical interference of native plants as a result of phenolics
produced in L. camara leaf litter. The ability of Lantana camara to increase soil pH,
phosphorus, nitrogen, manganese, iron and total organic carbon (Subha & Chandra, 2018),
alters the soil conditions thus reducing the growth and health of most native plant species
(Parveen, et al., 2011).
20
5.2.2 Effect of Lantana camara on plant species diversity
According to (Parveen, et al., 2010), Lantana camara has a dense root network and high
efficiency of scarce nutrients uptake compared to most native shrubs hence deprives other
shrubs of vital growth nutrients by outcompeting them.
From the Shannon’s index values obtained, species diversity was found to be high in the
uninvaded communities than in the invaded communities same as (Yusuf, et al., 2013). This
was due to the fact that the uninvaded communities have more species and high species
abundance than the invaded communities. The less species diversity of the invaded
communities is justified on grounds that L. camara occupies the larger space and thus
suppressed and inhibited growth of intolerant plant species especially graminoids and
herbaceous plants.
5.2.3 Effect of Lantana camara on plant species density
The uninvaded communities had a higher mean plant species density of native plant species
than the invaded communities similar to the findings obtained by (Sheunesu, 2020).
Graminoids in the invaded communities had a very low density per hectare, moreover being
the major economic drivers of Kakiika, the case that compromises economic development of
the area since it leads to low farm production of livestock, mainly cattle which entirely
depends on these graminoids. Sporobolus pyramidalis and Brachiaris decumbens, the grass
species with the highest densities in the uninvaded communities were not recorded in the
invaded communities, and yet they form the largest percentage of forage for castle and this
may ultimately reduce the palatable pastures available to support large cattle herds and this
would result into low cattle production. Only three grass species were recorded in the invaded
communities and these are Digitarlia ciliaris, Kyllinga alba and Panicum maximum with
plant densities of 37000, 14000 and100 individuals/hectare respectively. However, Digitarlia
ciliaris had a higher density in the invaded communities than in the uninvaded communities
(31000 individuals/hectare). The other two grass species found in the invaded communities
had lower densities compared to that of the uninvaded communities.
Forbs were greatly affected by the invasion of Lantana camara also where their mean species
densities were lower in the invaded compared to the uninvaded communities. Tree and shrubs
mean species densities were also lower in invaded than uninvaded communities similar to
findings of (Ashok & Anup, 2017). Markharmia lutea was found to have the highest density
than any other tree species in both the invaded and uninvaded communities with the invaded
communities having the highest density, meaning that the invasion of Lantana camara
favoured this species. The exception was with the climbers where their mean species
densities were higher in invaded communities than uninvaded communities.
21
5.3 Effect of Lantana camara on level similarity between invaded and uninvaded
vegetation communities.
The overall level of similarity between the invaded and uninvaded vegetation communities
was found to be very low, where the Jacquard coefficient of similarity was used. The
obtained Jacquard index were below 0.5 (a minimum value for similar communities) and
hence the invaded and uninvaded communities were dissimilar. (Ravinder, et al., 2009) used
Sorensen’s index and established low similarity between invaded and uninvaded vegetation
communities similar to the findings of this report.
5.4 Impact of Lantana camara invasion on plant species cover
The overall mean percentage cover trees, shrubs, forbs and graminoids was high in uninvaded
communities compared to that of the invaded communities similar to the findings of
(Sheunesu, 2020). Also (Peter, 2007) studied the impact of Lantana camara on native
vegetation in Northern Gonarezhou National Park, Zimbabwe and established that the
invaded communities had low plant species cover compared to the uninvaded communities.
Climbers however, had a higher species percentage cover in the invaded communities than
uninvaded communities indicating that the invasive species favoured growth of these
climbing species.
The biggest concern would be about the cover of graminoids which form the major economy
drivers of the Kakiika since the main economy activity is livestock farming, basically cattle
keeping. These vast cattle farms depend on graminoids dominated by Brachiaris decumbens
and Sporobolus pyramidalis to support large herds of cattle and therefore any disturbance that
reduces the cover of graminoids has a direct negative impact that results in reduction of the
cattle and other animals’ productivity. Due to the fact that there was not enough grass cover
to provide sufficient forage for cattle in the invaded communities, invaded vegetation
communities are therefore not suited for cattle ranching since there is no pasture to support
the high forage demand of cattle. The wooded grasslands were dominated by acacias as trees.
Further concern is about particular shrub species that are preferred by goats which are other
animals kept in Kakiika second to cattle. It was found out that the invasion of Lantana
camara inhibits the growth of important Acacia hockii, and other acacia shrubs which are the
most important in providing forage for goats. This may pose a negative impact on the
productivity of goats.
22
6 Conclusion and recommendations
6.1 Conclusion
Lantana camara reduces the plant species cover of native plant species and poses a threat on
rangeland productivity by supressing the grass species and other important shrubs that
support the productivity of the rangeland.
6.2 Recommendations
Sustainable control measures should be taken to eliminate Lantana camara from the invaded
areas and stop its further spread so as to improve and maintain the overall health of Kakiika’s
rangelands to ensure their maximum sustainable productivity.
23
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