http://www.bioline.org.br/pdf?ja08049
* Corresponding author: Muhammad Zafar Iqbal
JASEM ISSN 1119-8362
All rights reserved
J. Appl. Sci. Environ. Manage. September, 2008
Vol. 12(3) 51 - 60
Full-text Available Online at
www.bioline.org.br/ja
Ecological surveys of certain plant communities around urban areas of Karachi
MUHAMMAD, ZAFAR IQBAL; SHAH, S. Z.; SHAFIQ, M.
Department of Botany, University of Karachi,Karachi- 75270, Pakistan
Email Add: shafiqeco@yahoo.com. shafiq_ecopk@hotmail.com
ABSTRACT: A phytosociological study was conducted as an initial assessment of the vegetation on different
sites to determine the community structure and how the communities were related based on their species composition
and edaphic characteristics. The communities were distinct types ranging from halophytes to xerophytes with
disturbed in nature. Plant communities based on first leading dominant species (Prosopis, Avicennia, Gynandropis,
Salvadora, Ipomea, Halopyrum, Limonium, Abutilon and Calotropis) were explored in the study area. Out of thirtynine plant species, Prosopis juliflora attained the highest total importance value index (I.V.I.) followed by Avicennia
marina, Suaeda fruticosa and Gynandropsis gynandra. Nine species attained first leading position. Thirteen species
attained second dominant position. However, twelve species attained third dominant position in all stands. P. juliflora
was the only species that was found six times as a first dominant, three times as second and one time as a third
dominates species. None of the other species was in a position to get first, second and third position as a leading
dominant in all stands. The communities were of heterogeneous type, with low species diversity and ranged from
1.36 to 4.54. Most of the plant communities showed less than 50% CMI values. However, Prosopis in association
with Pasplidium and Cenchrus community showed highest CMI value (70.00). The soils of the study areas were
sandy loam, loamy sand, loamy silt, sandy and silty. The soils are alkaline in nature. An appreciable amount of
calcium carbonate (13-26%) with moderate percentage of maximum water holding capacity (19-41%) and high soil
EC (593 s/cmµ) were recorded. It was also observed that certain edaphic and human activity, discharge of pollutants
with out any pretreatment was found responsible for variation in the nature, structure and composition of vegetation.
The plant growth and their continuity was in danger in many disturb areas, especially in some coastal areas where
salinity and the incident of Tasman spirit oil spillage was occurred just few months before the survey carried out.
Construction of flyover, expansion of the roads and cut down of the natural vegetation producing additional losses to
flora of the region. @ JASEM
The ecological surveys are necessary for an
adequate characterization of a plant community.
Disturbed areas considered those, where the
integrity of the natural setting and natural system
processes has been directly or indirectly affected by
human activities. These activities could be for
resource extraction, visitor use, development of
maintenance, or invasion of nonnative sp. etc. The
vegetation in the disturbed areas does not reflect a
naturally evolved species composition, but rather a
mixture of small remnant patches dominated by
native plants patches of largely invasive weedy
alien plants, and areas of mixed native and non
native plants. All over the world, natural habitats
are being degraded. There is evidence of
contamination in the most remote parts of the
world. The human population is getting larger,
spreading and producing more complex and
interactive disturbance on plant communities.
There are few undisturbed habitats are left in some
most part of the world. Nevertheless, there is also a
general desire to maintain natural habitat for our
enjoyment and for the continue well-being of
nature. Plant ecologist have placed increasing
emphasis on a gunctional understanding of
vegetation (Lehsten and Kleyer, 2007). The
response of plant communities to environmental
change is often studied by analysing the
composition of plant traits across communities. A
lot of work has been done in ordinating the
tropical, temperate, deciduous, desert and
calcareous types of vegetation, whereas littler work
has been reported from disturbed vegetation. The
ecological survey of such disturbed areas
conducted by few researchers, in order to know the
damage done to ecology of the area and also to
know the diversity and dispersion status of species
in the area. In Pakistan some phytosociological
studies on plant communities of different areas
have been conducted (Akbar and Ahmed, 1991;
Dasti and Agnew 1994; Iqbal, 1998). Arshad, et al.,
(2002) carried out a phytosociological assessment
of natural reserve of national park Lalsuhanra and
identified three distinct types of plant communities.
Ahmed and Khattak, (2001) in quantitative studies
on the vegetation of Islamabad concluded that due
to large scale artificial addition the original
vegetation is vanishing at certain places.
Khan et al., (1999) have described structure,
composition and above ground standing phytomass
for the summer aspect of some grass dominated
communities of Karachi. In another studies, Khan
and Shaukat (2005) have described above ground
standing phytomass of some grass-dominated
communities of Karachi for winter aspect. In past,
few ecological studies have been made on the plant
communities of different areas of Karachi (Shafiq,
et al., 1992, Khan, 1993, Iqbal and Hussain, 1994;
Iqbal and Shafiq, 1996, Iqbal, et al., 1998; Khan
and Shaukat, 2005). Karachi is the biggest city of
Pakistan. The city has more than 12 million
population and ranked the 10
th
amongst the biggest
cities of the world. Increasing population pressure,
expansion in industrial and residential areas,
construction of roads, flyovers and invasion of
nonnative species activities affected nature,
structure and composition of the plant
communities. Almost each and every area of the
Karachi can be presented as the classical example
of disturbance and pollution impact on plant Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
52
communities. The city atmosphere is being affected
badly by almost every type of environmental
pollution. The natural vegetation of the region is
either being replace by invasive species or is being
removed by man for the construction of roads,
flyover, building and industries. Dumping of
domestic and industrial trash in Malir, Lyari and
Hub rivers is also a common practice in the city,
which has also affected the indigenous
biodiversities of these wetlands. The aim of
present investigation was to provide quantitative
description of the vegetation on the disturbed areas
of the Karachi city, which is changing from natural
to semi-natural form due to anthropogenic
disturbances, which are still in progress.
MATERIALS AND METHODS
A: Description of the area
The bioclimate of Karachi in the Holdridg’s system
falls in the category of “Tropical Bush Formation”.
The rainfall is irregular and average below 200 mm
a year mostly in summer. The winter peak of
precipitation is very low. Winter is the driest part
of the year. Summer, which is very hot, the winter
in this part of world is mild. Mean monthly
minimum temperature for the month of January
remains around 10°C-12.5°C due to the Siberian
winds. The insulation is intense with global solar
radiation varying from 3580 Kcal.m
-2
day
-1
for
December to 5609 Kcal M
-2
day
-1
for May. The
diffused radiation is 20-30% of the global radiation
(Ahmed et al., 1991) Rain in Karachi is seasonal,
averaging less than 22 cm per year between June
and September and rare for the remainder of the
year. Occasionally, there are dry years too while
strong coastal winds and better dew formation is
the characteristic feature of Karachi.
B: Vegetational survey
A phytosociological survey of different habitats of
Karachi was carried out in the months from July to
October 2003 (Fig. 1). The study area is comprised
of more than 30 square kilometer. Areas were
sampled by Point centered quarter methods
(Cottom and Curtis, 1956). Twenty sampling points
were established at each venue with regular interval
by spacing ten steps. Relative cover, relative
frequency, and relative density were obtained. The
importance value index (I.V.I.) for each species
was obtained by addition of the above community
attributes (Curtis and McIntosh, 1951). The
community was named according to dominant
species, which have highest I.V.I. Homogeneity of
community was determined by Raunkiaers Law of
frequency (1934). Community maturity index was
found by Pichi-Sermoli (1948) and species
diversity index was determined by the following
formulae of Simpson index.
D = N (N-1) / Σ n (n-1)
D = Diversity index
N = Total number of plants of a species
n = number of individuals
Σ = Sum of all individuals of a species.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SITES
Diversity Index Value
Fig. 1. Species diversity index
SAMPLING SITE: 1=Near hawksbay; 2= Manora; 3=Karachi University Stop; 4=Saeedabad Baldia Town;5= Peoples’s ground; 6=
ManoraGraved;7= Malir river at Korangi crossing; 8= Malir river around Malir river;9= Mikolachi Road;10= Korangi No.5 Shahra -e-
Uloom;11= Mikolachi road;12= Hawksbay;13= Gaboput Kamri; 14= Bahraria complex II;15=March Morr Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
53
Fig 1. MAP OF THE SAMPLING SITE: 1=Near hawksbay; 2=
Manora; 3=Karachi University Stop; 4=Saeedabad Baldia
Town;5= Peoples’s ground; 6= ManoraGraved;7= Malir river at
Korangi crossing; 8= Malir river around Malir river;9=
Mikolachi Road;10= Korangi No.5 Shahra -e- Uloom;11=
Mikolachi road;12= Hawksbay;13= Gaboput Kamri; 14=
Bahraria complex II;15=March Morr
C: Soil analysis
One composite soil sample from each stand was
also taken with the help of soil corer. The samples
were brought to the laboratory in polythene bags
for physical and chemical analysis. Soil texture was
determined by manual as well as mechanical
(sieving) methods. Soil structure was observed by
hand lens observatory methods. Maximum water
holding capacity (M.W.H.C.) of the soil was
calculated by the following formulae. M.W.H.C.
(%) = Loss in weight/oven dried weight of soil X
100.
The soil pH was determined by direct pH reading
meter (Model JENWAY PHM 6). Calcium
carbonate was determined by acid neutralization
method (Qadir et al., 1961). Electrical conductivity
(E.C.) of the soil samples was determined by
digital conductivity meter (Beckman’s conductivity
meter). Sodium contents of the soil were
determined by silver titration method (U.S.D.A.,
1951).
RESULTS
The vegetation of studied areas showed the
presence of halophytes, xerophytes and disturbed
type of vegetation. A summary of
phytosociological data is summarized in (Table 1).
Among all the listed thirty nine plant species,
Prosopis juliflora was found leading dominant in
most of the stands. The stands dominated by
Prosopis, formed an association with halophytes
(H. recurvum, T. indica, C. cretica) and xerophyte
(C. procera, S. oleoides, F. indica, P. aceolata)
species. Avicennia marina as a leading dominant
formed an association with halophytes (C. cretica,
S. baryosma. S. fruticosa) and showed complete
absence of disturbed species (P. juliflora, A.
javanica, S. holoseracea, A. indicum, F. indica, S.
ovata). Whereas, Abutilon and Calotropis procera
as a leading dominant showed complete absence of
other halophytes. Salvadora formed an association
with disturbed species P. juliflora, and halophyte S.
fruticosa. The stands, dominated by Limonium
stocksii showed an association with both disturbed
(P. juliflora) and grass species (Aleuropus). The
stand dominated by Gynandropsis did not form any
association with halophytes and formed an
association with disturbed (P. juliflora) and
xerophytic species (T. terristris).
Homogeneity of Communities: The frequency
distribution of all communities showed
heterogeneous types of vegetation, which is in
accordance with the Raunkiers law of frequency.
Absence of certain classes in frequency distribution
of all communities makes heterogeneous types of
vegetation.
Community Maturity Index (C.M.I.): This index
is an important indicator for the maturity of the
communities (Table 2). Most of the plant
communities showed less than 50% CMI values.
However, Prosopis in association with Pasplidium
and Cenchrus community showed highest CMI
value (70.00). Similarly, Prosopis in association
with Suaeda and Tamarix community showed
higher CMI value (56.25). Prosopis in association
with Calotropis and Cenchrus showed less than
(50.00) CMI value which proved the immaturity of
vegetation (Table 3). Avicinnea community had
lowest CMI values (10.00). Ipomea and Avicinnea
in association with Cressa-Salsola had better CMI
45.83 and 40.00 values, respectively. Gynandropis,
Limonium and Salvadora had CMI less than 40. A
better CMI value 32.11 and 26.25 was found in
Calotropis and Abutilon community.
Species diversity: The species diversity index
(Simpson’s index) is another important value for
the community studies. Higher species diversity
value is a characteristic of stable communities. The
species diversity of the studied communities was
generally low and ranged from 1.36 to 4.54 (Fig.
1). The highest species diversity (4.54) was
observed in Prosopis community. The Avicenea
and Ipomea sp community had better species
diversity (4.01) while, the lowest species diversity
(1.36) was observed in Gynandropsis community. Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
54
Table 1: Phytosociological summary of the community attributes
Sp. No Species name No of
times sp.
occurred
in stand
Importance Value Index
(I.V.I.)
No of stands
dominant
Total
IVI
Ave.
IVI
Max.
IVI
Min.
IVI
1st 2nd 3rd
1. Prosopis juliflora Swartz 12 1280 107 198 27 6 3 1
2. Avicennia marina 2 335 167 208 127 2 - -
3. Suaeda fruticosa (L.) Forssk. 7 270 39 74 13 - 1 3
4. Gynandropis gynandra (L) Briq. 1 170 170 170 170 1 - -
5. Salvadora persica L. 2 153 76 144 9 1 - 1
6. Cenchrus barbatus Schum 4 131 33 84 8 - - 2
7. Ipomoea sindica (Stocks) Stapf 2 129 64 121 8 1 - -
8. Halopyrum mucronatum (L.) Stapf 1 106 106 106 106 1 1 1
9 Convolvululs glomerates Choisy 3 104 34 80 80 - 1 1
10. Limonium stocksii (Boiss) O. Ktze 1 103 103 103 103 1 - -
11. Salsola brayosma (R. & S.) Dandy 5 101 20 40 7 - - 1
12. Cressa cretica L. 3 96 32 48 15 - 2 1
13. Senna holosericea (Freson.) Greuter 3 77 25 32 21 - - 1
14. Calotropis procera (Willd.) R.Br. 3 76 25 37 4 1 1 -
15. Heliotropium subulatum (D.C.) Vatke 2 72 36 58 13 - - -
16. Cenchrus biflorus Roxb. 2 56 28 41 15 - -
17. Pasppalidium geminatum (Forsk) Stapf 1 54 54 54 54 - 1 -
18. Tribulus terristris L. 1 51 51 51 51 - 1 -
19. Aeluropus macrostachyus Hack. 2 50 25 36 14 - - 1
20. Zizyphus numularia (Buurn. f.) Wight &
Arn.
3 38 13 21 9 - - -
21. Aeluropus lagopoides (L) Trin.ex. Thw 1 37 37 37 37 - - -
22. Fagonia indica (L.) 2 35 17 19 6 - 1 -
23. Sida ovata Forrsk. 1 35 35 35 35 - - 1
24. Urochondra setulosa (Trin.) C.E. Hubb 1 25 25 25 25 - - -
25. Abutilon indicum L. Sweet 1 126 126 126 126 1 - -
26. Arthrocenemum macrostachyum 1 32 32 32 32 - -
27. Atriplex stocksi Boiss 1 21 21 21 21 - - -
28. Indigofera oblongifolia Forsrsk. 1 19 19 19 19 - - -
29. Dichanthium annulatum (Forrsk.) Stapf 2 19 9 10 9 - - -
30. Eragrostis pilosa ( L.) Beauv. 1 17 17 17 17 - - -
31. Zygophyllum simplex L. 2 16 8 8 8 - - -
32. Cenchrus setigerus Vahl 1 15 15 15 15 - 1 -
33. Aerva javanica (Burm. f.) Merrill 1 32 32 32 32 - 1 1
34. Parkinsonia aculeate L. 1 75 75 75 75 - 1 -
35. Heliotropium curassavicum L. 1 9 9 9 9 - - -
36. Sporobolus marginatus non Hoehst 1 9 9 9 9 - - -
37. Acacia nilotica (Linn.) Delile 1 8 8 8 8 - - -
38. Capparis decidua (Forssk.) Edgew. 1 6 6 6 6 - - -
39. Tamarix indica Willd. 1 6 6 6 6 - - 1
The disturbance: The disturbances were of
various type and degree on the study sites (Table
2). One thing was common that the disturbance was
a mean to reduce species diversity and to reduce
plant growth. The phenology of the plants on
disturbed areas was not good although they had
received a good shower in the monsoon season
couple of months back.
Soil Characteristics: The soil of the study area
was alkaline in nature with loamy sand, sandy
loam, loamy silt and silty having a considerable
amount of calcium carbonate, which is a
characteristic feature for arid soil. Eight stands
were found on loamy sand and three on loamy silt
while two on silty and two on sandy loam (Table
3). Fifteen plant communities were identified.
Propsopis community formed six different types of
association (Prosopis-Paspilidium-Cenchrus,
Prosopis-Calotropis-Salvadora, ProsopisCenchrus-Cressa, Prosopis-suaedea-Tamarix,
Prosopis-Parkinsonia-Halopyrum and ProsopisFagonia-Cenchrus) times leading first dominant
species. Similarly, Avicenia community formed
two types of community as Avicenia-CressaSuaeda and Avicenia-Cressa-Salsola respectively.
Therefore, these communities were explored as
(Prosopis, Avicennia, Gynandropsis, Salvadora,
Ipomea, Halopyrum, Limonium, Abutilon, and
Calotropis) community and their edaphic
characters are explained as follows: Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
55
Table2: Community Maturity Index (C.M.I.), study site, nature of disturbance and total number of species in stand
Table 3. Soil characteristics of different disturbed habitats
Plant community Soil Characteristics
Soil
texture
Soil
structure
Sand
%
Silt
%
Clay
%
MWHC
%
pH CaCO3
%
EC
µs/cm
Na
ppm
Halopyrum-ConvolvolusSuaeda
SL-LS RP 81 12 4 23 7.54 13 242 146
Avicenia-Cressa-Suaeda LS-SL RP 84 10 5 19 7.56 21 473 285
Ipomea-HalopyrumConvolvolus
SL-LS RP 82 11 4 22 7.53 13 242 145
Gynandropsis-TribulusProsopis
LST RNP 17 58 24 41 7.85 26 593 357
Limonium-Prosopis-Aleuropus LST RNP 9 57 31 45 7.85 26 593 357
Prosopis-PaspalidiumCenchurs
LST RNP 5 58 37 48 7.85 23 590 355
Avicenia-Cressa-Salsola ST RNP 4 90 5 40 7.86 21 473 285
Salvadora-Prosopis-Suaeda ST RNP 5 88 6 39 7.85 22 593 357
Prosopis-Calotropis-Salvadora LS, S AB 87 8 4 19 7.20 14 242 145
Prosopis-Cenchrus-Cressa LS, S AB 87 8 4 19 7.10 14 241 145
Prosopis-Suaeda-Tamarix LS, S RP 85 10 4 19 7.85 26 593 357
Prosopis-ParkinsoniaHaloxylon
LS, S RP 87 8 4 19 7.35 26 593 357
Prosopis-Fagonia-Cenchrus LS, S RP 87 8 4 19 7.45 16 323 195
Calotropis-Aerva-Senna LS RAB 83 13 5 19 7.42 16 399 240
Abutilon-Prosopis-Sida LS-S RAB 87 8 4 19 7.45 16 333 201
Symbol Used:
SL=Sandy loam, LS=Loamy sand, LST=Loamy silt, S=Sandy, ST=Silty, RP=Rounded (porous), RNP= Rounded (non porous), AB=
Angular blocky, RAB= Rounded+Angular blocky, MWHC= Maximum water holding capacity of soil , EC= Electrical Conductivity of
soil
Prosopis community: Prosopis community formed
six different types of association with halophytic
and xerophytic species such as H. recurvum, C.
cretica, S. fruticosa and T. indica. The soil
characteristics of Prosopis community showed
variation in the nutritional value of soil
characteristics. This community in association with
C. procera, S. persica, C. barbata, C. cretica, S.
fruticosa, T. indica, P. aceolata, H. mucronatum
and F. indica preferred to grow on high percentage
of sand (85-87%) and low amount of silt (8-10%)
and clay (4%) particles. The community had low
percentage of maximum water holding capacity
(19%). Whereas, Prosopis community in
association with P. gyminatum and C. setigerus
preferred to grow on highest percentage of silt
(58%) and Maximum Water Holding Capacity
(48%). The soil of the community had better
calcium carbonate (23%) with alkaline soil pH
(7.10-7.85). The concentrations of sodium content
were found in the range of 145-357 ppm. The
community preferred electrical conductivity (EC)
in the range of 241-593 µs/cm.
Stand
No.
Plant Community Study site Disturbance CMI Total No
of species
in stands
1 Halopyrum-Convolvolus-Suaeda Manora Graved Naval activities 50 8
2 Avicenia-Cressa-Suaeda Manora Construction of road 10 6
3 Ipomea-Halopyrum-Convolvolus Gaboput Kamri Salinity, polluted sea water 46 6
4 Gynandropsis-Tribulus-Prosopis Near hawksbay Salinity 31 5
5 Limonium-Prosopis-Aleuropus Hawksbay Salinity 38 8
6 Prosopis-Paspalidium-Cenchurs Malir river around
Malir river
Water, air pollution 70 4
7 Avicenia-Cressa-Salsola Malir river at Korangi
crossing
Traffic, air and water
pollution
40 8
8 Salvadora-Prosopis-Suaeda Mikolachi road Tasman strip 38 6
9 Prosopis-Calotropis-Salvadora March Morr Lyari express way 39 6
10 Prosopis-Cenchrus-Cressa Peoples’s ground Traffic, air and dust
pollution
35 6
11 Prosopis-Suaeda-Tamarix Mikolachi Road Tasman strip spill 56 4
12 Prosopis-Parkinsonia-Haloxylon Bahraria complex II Construction 35 7
13 Prosopis-Fagonia-Cenchrus Saeedabad Baldia Town Houses,road construction 20 9
14 Calotropis-Aerva-Senna Karachi University Stop Plaza construction 32 7
15 Abutilon-Prosopis-Sida Korangi No.5 Shahra
-e- Uloom
Grazing, polluted water 26 8
Symbol used: CMI (Community Maturity Index) Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
56
Avicenia community: This community is
dominated by halophytes. The community formed
an association with other halophytes C. cretica, S.
fruticosa and C. certica. The community in
association with C. cretica and S. fruticosa
preferred to grow on high percentage of total sand
(84%) along with better percentage of silt (10%),
clay particles (5%) and low MWHC (19%). This
community prefers to grow on sandy loam to
loamy sand soil type. The soil of the community
had slightly alkaline pH (7.56) with high sodium
content (285 ppm) and electrical conductivity (473
µs/cm). While the same community in association
with C. cretica and S. baryosma preferred to grow
on highest percentage of silt (90%) along with low
percentage of silt (4%), clay particles (5%). The
community prefers to grow on better MWHC
(40%). The soil of the community had highest
alkaline pH (7.86).
Gynandropsis community: Gynandropsis formed
an association with T. terristris and disturbed
species, P. juliflora. This community prefers to
grow on loamy silt soil type. The community had
better percentage of total sand (17%), silt (58%)
and clay particles (24%). The maximum water
holding capacity of the soil was 41% and soil was
loamy silt. The soil pH (7.85) and Na
+
(357 ppm)
contents were moderate in the community. The
dominance of the community might be due to the
highest EC (593 µs/cm), EC (0.59 ds/m and
calcium carbonate (26%).
Salvadora community: S. persica formed an
association with both disturbed species, P. juliflora
and halophytes S. fruticosa. It appeared to grow at
the low percentage of total sand (5%), clay (6%),
high percentage of silt (88%) and better water
holding capacity (39%). This community prefers to
grow on silty types of soil. The community was
found to grow on high percentage of calcium
carbonate (22%) as compared to other plant
communities. The community had slightly alkaline
soil pH (7.85), EC 593 µs/cm and sodium level,
and 357 ppm.
Ipomea community: Ipomea community formed
main association with halophytes (H. mucronatum)
and creeping C. conglomerates. The soil of the
community had a high percentage of total sand
(82%) with better percentage of silt (11%) and clay
(4%) particles. The soil was sandy loam and loamy
sand with slightly alkaline pH (7.53). The
community showed moderate concentration of
calcium carbonate (13%), Na
+
salt (242 ppm) and
EC 242 µs/cm, respectively.
Halopyrum community: Halopyrum community
formed main association with halophytes S.
fruticosa and creeping plant species C.
conglomerates. The community was found on soil
having high percentage of total sand (81%) with
lowest percentage of clay particles (4%). However,
the amount of silt was moderate (12%). This
community prefers to grow on sandy loam to
loamy sand. The community prefers to grow on
better water holding capacity of soil (23%). Lowest
percentage of calcium carbonate (13%) was
observed in this community. Other soil
characteristics of community such as EC, Na, K
and pH were low.
Limonium community: Limonium community
formed main association with disturbed species P.
juliflora and grass A. lagopoides. Species C.
conglomerates. The community was found on soil
having low percentage of total sand (9%) with high
percentage of clay particles (31%). However, the
amount of silt was moderate (57%). However, the
water holding capacity of community soil was
moderate (45%). This community prefers to grow
on loamy silt soil type. The community had high
calcium carbonate (26%). The other soil
characteristics such as pH (7.85), EC (593 µs/cm)
and Na (357 ppm) were high.
Abutilon community: Abutilon community formed
main association with disturbed species P. juliflora
and xerophytes S. ovata. The community was
found on soil having high percentage of total sand
(83%) with better percentage of clay (5%) and silt
particles (13%) and prefers to grow on sandy to
loamy sand types of soil. The community had the
low water holding capacity of soil (19%) along
with better amount of calcium carbonate (16%).
The other soil characteristics such as pH (7.42), EC
(399 µs/cm) and Na (240 ppm) were moderate.
Calotropis community: Calotropis community
formed main association with xerophytes species
likewise A. javanica and S. holosericea. This
community preferred to grow on loamy sand soil
type. The community was found on soil having
high percentage of total sand (87%) with lowest
percentage of silt and clay particles (4%). The
community had the lowest water holding capacity
(19%). The other soil characteristics such as pH
(7.45), EC (333 µs/cm) and Na (201 ppm) were
moderate.
DISCUSSION
In order to assess ecological knowledge of the
native flora in southern site of Pakistan, a
quantitative phytosociological study in different
areas of the city was carried out. Importance value
index (I.V.I.) for each plant species was determined
to quantify the importance of each species. The
vegetation of the studied sites is composed of
halophytic, xerophytic and disturbed species. The
disturbance is mainly due to the construction of
roads, flyover, salinity, discharge of pollutant on
soil surface without any pretreatment and animal
grazing. These activities are responsible in Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
57
converting natural vegetation to semi natural
vegetation. An important component of any
ecosystem is the species it contains. Species also
serves as good indicators of the ecological
condition of a system (Morgenthal, et al., 2001). A
list of all species collected during the study was
compiled. The floristic composition of different
area was also compared. The species composition
of the fifteen stands was considerably different.
Halophytes were, for example, more abundant on
the soil having high salt content in the area.
Vegetation analysis gives the information
necessary to determine the name of community and
provide data that can be used to compare it with
other communities. Nine plant communities;
Prosopis, Avicennia, Suaeda, Gynandropsis,
Salvadora, Ipomea, Limonium, Calotropis and
Abutilon were observed as a leading dominant. The
leading dominants of one stands was also found in
other stands as co-dominant. The communities in
the study area were heterogeneous. The absence of
certain frequencies classes in the communities
reflected the heterogeneity of the vegetation, which
is either due to biotic disturbance or the floral
poverty. The result obtained by Raunkiaer (1954)
may be regarded only as possibilities to be
confirmed by other alternative approaches.
The concept of species diversity relates simply to
“richness” of a community or geographical area in
species. At the simplest level of examination,
species diversity corresponds to the number of
species present. Species diversity is considered to
be an important attribute of community
organization and allowed comparison of the
structural characteristics of the communities. It is
often related to community dynamics stability,
productivity, integration, evolution, structure and
competition. The idea of displacement of one
species through competition with other is net prime
importance. The species diversity was low and the
community maturity index was below 50%, which
indicates that the communities are under several
changes except stands dominated by ProsopisPaspalidium-Cenchrus and Prosopis-SuaedaTamarix community. This might be due to
occurrences of lowest number of plant species
present in stand and variation in edaphic
characteristics of community. Furthermore,
variation in plant growth due to changes in edaphic
and climatic conditions in S. fruticosa (L.) and
Tamarix indica Willd from the saline community
of Karachi University Campus was investigated
(Maryam, et al., 1995). The halophytes besides
having sand binding and salt absorption properties
also have a great economic importance for use as a
forage, fodder, oil crops, pulp, paper industry and
fuel wood (Malcolm, 1993). High percentage of silt
(58%), clay (37%), and maximum water holding
capacity of soil (48%) in Prosopis-PaspalidiumChencrus community might be reason of such
change. The findings are similar to the
investigation of Matthews, et al., (2001). In
hierarchical classification, vegetation map,
description and ecological interpretation of the
plant communities of the Tembe Elephant Park and
surrounding areas dynamics of water in the
landscape either directly or indirectly, through its
role in moisture levels and soil formation play a
role in the determination of plant communities at
the higher levels. Species richness was found to be
highest in associations with high structural
diversity and species turnover was strongest where
environmental heterogeneity was high (Hoare and
Bredenkamp, 2001). A strong dominance by P.
juliflora is likely to continue within the both
disturbed and halophyte community type.
Establishment by the co-dominant, S. fruticosa
suggests an increasing importance of this species.
However, P. juliflora in association with F. indica
and C. procera appears to be particularly adapted
to the xeric condition of soil Similar types of
vegetation around the Lyari river was found and
mostly dominated by monocotyledonous species
viz Paspalidium geminatum, Cyperus laevigatus,
Chloris barbata and Aeluropus lagopoide. (Iqbal
et al., 1998). P. geminatum was the most common
and widely distributed species along the waste
effluent in the study areas. Plant growth and
development are the result of many physiological
processes, which are influenced by soil moisture
(Mondal and Paul, 1992; Begum and Paul, 1993).
Distribution of plant communities mostly depends
upon the edaphic factors, like, soil texture,
structure, pH, moisture and mineral composition.
Soil salinity alone of in combination with water
logging play an important role in distribution of
halophytes. Variation in total salinity, depth of soil
horizon and extent of water logging can greatly
influence the vegetation of an area including
halophytes (Maryam, et al.,1995). Prosopis
community preferred to grow on wide range of
water holding capacity of soil 19-48%, resulting in
the formation of six different types of plant
association.
Differences in rehabilitation treatment, age of
rehabilitation and man-made disturbances were
observed in some of the important factors
determining the establishment of different
communities, such as on ash disposal sites.
Statistically significant differences were found in
the diversity of vegetation on a community and
variant level (Morgentha, et al.,2001). One of the
main factors influencing plant distribution is the
type of soil. Most plants are specially adapted to
more or less specific soil types. The distribution
and composition of plant communities is there's
seems to be affected by climatic and underlying
edaphic factors. The soil of the study area was
alkaline in nature with sandy loam, loamy sand,
loamy silt, sandy and silty. An appreciable amount
of calcium carbonate is a common feature of arid
area soil. Soil of the communities showed
significant variation in their characteristics.
However, some communities recognized in the Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
58
study area are also found in other parts of the
country. The construction of flyover, roads,
salinity, indiscriminate discharge of pollutant,
dumping of soil waste and increasing human
activities disturbing the natural vegetation pattern
of the study areas. Similar conclusion was drawn
by Akbar and Ahmed (1991) about the vegetation
of Quaid-e-Azam University campus. Out of 39
species, eighteen species were occurred as a first,
second or third dominant in community. Maximum
numbers of species (9) were found in ProsopisFagonia-Cenchrus community. The number of
species per site varied with the species dominating
the site and the soil characteristics of the site.
Halophytic communities were composed of lesser
number of species as compared to glycophytes
communities (Khan and Shaukat, 2005). The
natural vegetation of all the three sites in the
reserve areas of Natural Park Lalsuhanra was
mainly herbaceous but in degrading form. Because
of overgrazing, the vegetation cover in unfenced
desert areas was in decreasing state as compared to
protected area (Arshad, et al., 2002). Reduction in
number of species was noted in few stands due to
pollution area as compared to other areas. The
presence of P. geminatum as a co dominant
population suggested that this species has tolerance
to pollution condition. In physiological mechanism
of pollution injury, many factors such as light,
wind, water, temperature and mineral nutrient
affects the responses of plants to pollutant. The
soil characteristics along water channels showed a
significant correlation with vegetation type. P.
Juliflora had wide ecological amplitude and was
found as a first dominant in different stand with a
range (7.10-7.85) of soil pH. A change in pH
values caused changed in association between
species. (Iqbal, et al.,1998).
Calcium carbonate is widely distributed in soil
occurring separately or they may be associated with
other salts. Hawksbay area soil has better
concentration of calcium carbonate. High
percentage of calcium carbonate made the
biological activity high, which make the soil fertile.
A variation in calcium carbonate concentration had
also showed relationships with vegetation types. G.
Gynandra formed a dominant community at the
highest concentration of CaCO3.The amount of
exchangeable sodium was found in appreciable
concentration, as in arid area. Where precipitation
is insufficient to leach out the soluble sodium salts.
A variation of concentration of sodium salts had a
marked influenced on vegetation. At lowest
concentration of sodium 146 ppm, Halopyrum
community preferred to grow in association with C.
glomeratus and S. fruticosa. Halopyrum
community preferred to grow on better edaphic
variable (pH 7.45, CaCO3 16%, and sodium salt
201 ppm) helped in the formation of xerophytic
and disturbed types of vegetation.
The ecology of different plant communities from
different sites of Karachi, showed variation in
nature, structure, composition of vegetation and
soil characteristic. Most of the species were
halophytes, xerophytes and in disturbed nature. The
majority of individuals of plant population were
seen in danger. Various types of activities have
modified the plant cover over wide areas. There is a
need to develop plant-protected areas. Cultivation
of wild species and grasses will help in soil binding
and maintaining the richness of the nutrient cycle
of the soil. Scientific information relating to the
composition of vegetation can be helpful for proper
rehabilitation of the affected area because this
forms the basic element for the conservation of
important and endangered flora and fauna of any
region. Protection of the natural flora from over
grazing is necessary, especially during the time
when the desirable plants set their seeds. Protection
is essential to maintain the desirable forage plant
species in a good proportion, to avoid invader plant
species and to rehabilitate the destroyed natural
flora (Arshad, et al., 2002). We must carry out our
efforts to make a list of the plant species, which can
be lost from the natural environment, otherwise it
will leads to desertification. Desertification
associated with human activities has been
recognized over the past 2 decades as one of the
important facets of ongoing global environmental
change (Verstraete and Schwartz, 1991; UNEP,
1997; Huenneke, et al., 2002) and Species loss
can alter the goods and services provided by
ecosystems (Hooper, et al., 2005).
Community structure, on a variant level, is largely
determined by different treatments (seed mixtures
and soil preparations) that were used in the
rehabilitation of the ash disposal sites. Periodical
survey on natural plant communities by comparing
with plant communities of rehabilitated sites, on
dumps of domestic refuse, industrial refuses carried
out. The reconstruction of plant communities on
disturbed sites with a species composition similar
to that of the natural area will require allocation of
more financial inputs. The saving and
establishment of plant communities one of the
major tasks facing by ecologist. Extensive work on
the development of vegetation depends upon good
indigenous vegetation recovery. Preservation of
these communities especially within disturbed sites
is more generally, demands a unique and pressing
conservation challenge. Extinction of some rare
species would result in the increase of the
prevalence of relatively stable species, such as P.
juliflora. It is concluded that salinity, discharge of
different types of pollutant and various types of are
adversely affecting the nature, structure and
composition of plant communities. Construction of
buildings and roads in the area is additional source
of disturbance. It is suggested that the discharge of
untreated polluted water must be checked.
Plantation near the construction of new structure
and roads should be increased. Plant material and
soil analysis should be carried out periodically, to
monitor the toxic levels of pollutant. Periodical Ecological surveys of certain plant communities around urban areas of Karachi
* Corresponding author: Muhammad Zafar Iqbal
59
ecological survey, knowledge of vegetation and
their relationship with soil characteristic can be
helpful for future development project like
botanical garden. Plant ecological surveys of all the
disturbed and threatened areas on permanent basis
are required to know their current biodiversity
situation and future continuity status. Plantation of
indigenous plants in the city is necessary.
Government and we must try to support the civic
agencies to save the natural biodiversity of the area.
There is also a need to control on the sources of
disturbances and pollution causing damage to
natural vegetation. Establishment of plant-protected
area at the center of the city is suggested due to
large-scale reduction in number of species.
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