Vegetation and soil characteristics of the wasteland ofValika Chemical Industries near Manghopir, Karachi
Tariq Mehmood & M. Zafar Iqbal
Department of Botany, University of Karachi, Karachi-75270, Pakistan
(Received 7 October 1993, accepted 25 January 1994)
The vegetation of the wasteland of Valika chemical industries near Man-ghopir road, Karachi was studied. Nine plant communities were recognizedbased on dominant species. In these plant communities the vegetation wasdisturbed, mostly halophytic and dominated by Suaeda fruticosa, Tamarixindica, Salsola imbricata, Cressa cretica, Atriplex griffithii, Haloxylon recurvum,Indigofera hochstetteri, Prosopis juliflora and Chenopodium album. The physico-chemical properties of the soils were also analysed. Soil texture was mostlysandy loam, which exhibited slight variations in the water-holding capacity.The soils contained a sufficient amount of CaCO3
– and exhibited mostlyalkaline soil pH. The soils of the different plant communities had scarcely anyorganic matter or inorganic phosphorus. The exchangeable sodium in thesoils of many halophytic plant communities was high, with appreciableconcentrations of potassium.
©1995 Academic Press Limited
Keywords: chemical pollution; exchangeable sodium; exchangeablepotassium; inorganic phosphorus
Introduction
Industrial pollution has become a serious socio-economic problem in the heavilyindustrialized areas of the world and has become a global issue. Industrial pollution iscaused by the discharge of a variety of industrial pollutants in the form of gases, liquidsand solids which affect the physical, chemical and biological conditions of theenvironment and are detrimental to human health, fauna, flora and soil properties(Dueck & Endendijk, 1987). Industrial waste effluents have a disrupting anddeleterious impact on the ecosystem and can reduce the number of species in aparticular ecosystem and may lead to instability within plant communities.
On the Sind Industrial Trading Estate, Karachi, the Valika chemical industriesrelease industrial waste effluents which are carried away either through uncementeddrains or by surface flow, thereby adversely affecting the soil with a variety of toxicwaste effluents. Such soils become waterlogged and saline and support a halophytictype of vegetation (Iqbal et al., 1983).
Address for correspondence: M. Z. Iqbal, Department of Botany, University of Karachi, Karachi-75270,Pakistan.
Journal of Arid Environments (1995) 30: 453–462
0140–1963/95/040453 + 10 $12.00/0 © 1995 Academic Press Limited
Iqbal & Munir (1988) studied the industrial waste effluents and their impact ondifferent plant communities growing under diverse habitat conditions along thepolluted disposal channels of the Karachi industrial area. A similar type of study wasconducted by Wuncheng & Williams (1990), in which they determined the toxicity ofindustrial effluents against different species; they found that effluents from chemicalindustries were more toxic than other effluent sources.
The prime objective of this study was to investigate the impact of Valika chemicalindustrial waste effluents on physico-chemical properties of the soils and on the nearbyvegetation.
Materials and methods
Study area
The study was conducted on the Valika chemical industries wastelands nearManghopir, situated about 20 km north of Karachi University, (Karachi, 24°51'N,67°02'E). The Valika chemical industries produce various chemicals, such as textiledyes, acids, alkalies etc.
Phytosociological survey of the vegetation
A phytosociological survey of the vegetation was conducted over the period December1989 to February, 1990. Twenty stands were studied by the quadrat method. The areaof one stand was about 0·8 ha. Within each stand, 15 quadrats of 9m2 each, spaced at15 m intervals, were studied. The circumference of every individual species wasrecorded. Phytosociological attributes like cover, density, frequency and their relativevalues and the importance value of each species were calculated. Nine plantcommunities were recognized among the 20 stands on the basis of leading dominantspecies, which were determined by the Brown & Curtis (1952) method. Moreover, 18species occupied the first three dominant positions in the study area, which weredistinguished by their average importance value as well as soil characteristics.
Soil analysis
The study was based on the analysis of 20 soil samples which were taken within eachstand from a c. 30 cm deep profile. Soil texture was determined by the feel method asdescribed by Burnham (1980); maximum water-holding capacity was measured by themethod of Keen (1931). Soil pH was determined by a direct pH reading meter (ModelSP. 31 SUNTEX). Soil CaCO3
– was estimated by acid neutralization as described byAnon (1954). The amount of organic matter was obtained by the method of Jackson(1958). The inorganic phosphorus was estimated according to Fogg & Wilkinson(1958). Exchangeable sodium and potassium was determined by flame photometer(Model Corning Flame Photometer 410).
Results
Phytosociological data of the 20 different stands are summarized in Table 1. They arespecies of disturbed habitats. The stands dominated by the halophytic and succulentspecies such as Tamarix indica, which attained the highest importance value, followedby Suaeda fruticosa, Salsola imbricata syn. S. barysoma, Cressa cretica, Aeluropuslagopoides, Atriplex griffithii and Chenopodium album. Species of disturbed habitats such
T. MEHMOOD & M. Z. IQBAL 454
Tab
le 1
.S
umm
ary
of p
hyto
soci
olog
ical
attr
ibut
es
Tot
al N
o.T
otal
No.
of
stan
ds
inof
sta
nd
s in
whi
ch s
peci
es d
omin
ant:
whi
ch s
peci
esT
otal
Ave
rage
Max
imu
mM
inim
um
No.
Nam
e of
spe
cies
occu
rred
I.V.I
.I.V
.I.
I.V.I
.I.V
.I.
1st
2nd
3rd
1.Ta
mar
ix in
dica
Will
d13
753·
1057
·93
91·5
734
·28
43
32.
Sua
eda
frut
icos
a(L
.) F
orss
k.13
699·
2953
·79
109·
211
15·9
94
31
3.S
also
la im
bric
ata
For
ssk.
945
9·08
51·0
076
·81
21·1
03
20
4.C
ress
a cr
etic
aL
.9
427·
0647
·45
86·7
911
·69
21
15.
Ael
urop
us la
gopo
ides
(L.)
Tri
n. e
x T
hw.
1139
5·79
35·9
855
·53
10·7
00
12
6.A
trip
lex
griffi
thii
Moq
. var
.st
ocks
ii (W
ight
) B
oiss
.6
368·
2861
·38
68·1
946
·70
22
27.
Mol
lugo
lotio
ides
(L.)
Ku
ntz
e10
355·
6335
·56
67·7
27·
320
03
8.P
roso
pis
julifl
ora
Sw
artz
.6
346·
2657
·71
81·6
520
·49
13
19.
Che
nopo
dium
alb
umL
.9
338·
8637
·65
72·2
415
·26
12
010
.H
alox
ylon
rec
urvu
mB
un
ge e
x B
oiss
522
7·66
45·5
372
·53
17·4
72
01
11.
Hel
iotr
opiu
m c
uras
savi
cum
L.
417
4·75
43·6
871
·08
42·0
00
12
12.
Zyg
ophy
llum
sim
plex
L.
714
6·30
20·9
036
·69
7·85
00
113
.In
digo
fera
hoc
hste
tteri
Bak
er3
142·
9547
·65
82·8
326
·20
10
014
.O
chra
denu
s ba
ccat
us D
el.
513
5·72
27·1
439
·55
16·8
00
00
15.
Hib
iscu
s sc
indi
cusS
tock
s4
107·
2326
·80
34·9
516
·84
00
116
.S
enna
hol
oser
icea
(Fre
sen
.) G
reu
ter
410
5·68
26·4
268
·09
9·41
01
017
.Fa
goni
a in
dica
L.
410
1·30
25·3
244
·55
10·5
70
01
18.
Innu
la g
rant
ioid
esB
oiss
.2
86·9
543
·47
54·9
032
·05
00
119
.C
appa
ris
deci
dua
(For
ssk.
) E
dge
w.
282
·71
41·3
555
·58
32·1
10
10
20.
Phy
llent
hus
niru
riL
.4
80·6
620
·16
28·7
615
·44
00
021
.G
rew
ia te
nax
(For
ssk.
) A
sche
rs. &
Sch
wei
nf.
361
·93
20·6
418
·85
7·44
00
022
.Te
phro
sia
unifl
ora
Per
s. s
ubs
p. u
nifl
ora
360
·80
20·2
627
·16
12·1
60
00
23.
Pro
sopi
s gl
andu
losa
Tor
rey
142
·36
42·3
642
·36
42·3
60
00
24.
Ble
phar
is s
indi
ca S
tock
s ex
An
der
s2
41·7
020
·85
26·5
815
·12
00
025
.A
erva
java
nica
(Bu
rm. f
.) J
uss
.3
39·0
713
·02
23·8
46·
170
00
26.
Aca
cia
sene
gal(
L.)
Will
d.
236
·30
18·1
525
·65
11·2
20
00
27.
Chl
oris
bar
bata
Sw
.3
33·4
811
·16
14·9
25·
920
00
28.
Blu
mea
obl
ique
(L.)
Dru
ce2
24·8
612
·43
17·4
27·
440
00
I.V.
I. =
Im
port
ance
Val
ue
Ind
ex (
Rel
ativ
e d
ensi
ty +
Rel
ativ
e co
ver
+R
elat
ive
freq
uen
cy)
PLANTS AND CHEMICAL WASTE 455
as Prosopis juliflora, Zygophyllum simplex, Indigofera hochstetteri and Ochradenus baccatusalso exhibited high importance values in many stands.
Nine leading dominant species were chosen from among the 20 stands and the meanimportance value of each leading dominant species calculated (Table 2). Suaedafruticosa was found to be the leading dominant in four stands and exhibited strongassociation with Tamarix indica, Cressa cretica, Prosopis juliflora and Atriplex griffithiiwhile Haloxylon recurvum, Indigofera hochstetteri, Chenopodium album and Salsolaimbricata were completely absent. Tamarix indica also played a leading role in fourstands with a significant presence of Salsola imbricata, Suaeda fruticosa, Haloxylonrecurvum and Atriplex griffithii. The three stands dominated by Salsola imbricata showedstrong association with Tamarix indica, Prosopis juliflora and Suaeda fruticosa while therest of the species were completely absent. Haloxylon recurvum also played a leadingrole in two stands with significant presence of Tamarix indica, Suaeda fruticosa,Chenopodium album and also exhibited considerable association with Cressa cretica.
Soil characteristics
In most of the plant communities, the soil textures were sandy loams with moderatewater-holding capacities. The pH was alkaline with sufficient quantities of CaCO3
– inthe soil. Inorganic phosphorus and organic matter was low; sodium was fairly high withan appropriate amount of potassium also present (Table 3).
Correlation of soil characteristics with plant communities
Nine plant communities based on the leading dominant species were recognized andwere correlated with edaphic factors (Table 3).
1. Suaeda community. In this community, Suaeda fruticosa was widespread in thestudy site and found mainly in association with other halophytic species (Atriplexgriffithii, Heliotropium curassavicum, Tamarix indica and Cressa cretica) and also with thedisturbed habitat species (Ochradenus baccatus, Prosopis juliflora). The sandy loam soilexhibited moderate water-holding capacity (20·62%). The soil pH was alkaline (7·8)with appreciable amount of CaCO3
– (22·03%). There was a considerable amount ofinorganic phosphorus (43 p.p.m.) with low organic matter (4·07%). Exchangeablesodium (2300 p.p.m.) was high, compared to potassium (1571 p.p.m.).
2. Tamarix community. Tamarix indica was mainly associated with halophytic species(Haloxylon recurvum, Aeluropus lagopoides, Salsola imbricata) followed by the disturbedhabitat species (Fagonia indica). In this community the soil texture was a sandy loamwith a low water-holding capacity (18·73%). It also showed alkaline soil pH (7·9) withhigh soil CaCO3
– (25·06%). The high sodium (2475 p.p.m.) in the soil favoured thefrequent occurrence of halophytic species; potassium levels (1592 p.p.m.) were low.
3. Salsola community. This Salsola imbricata community was found in many standswith association of halophytic species (Tamarix indica, Suaeda fruticosa) as well asdisturbed species (Prosopis juliflora, P. glandulosa). The soils were a sandy loam with amoderate water-holding capacity (21·37%), sufficient amounts of CaCO3
– (23·16%)and a basic soil pH (7·6). The organic matter (4·28%) was moderate and inorganicphosphorus (31 p.p.m.) were low. The sodium content (2250 p.p.m.) was higher thanthat of potassium (1539 p.p.m.).
4. Cressa community. Cressa cretica was found to be associated with halophyticspecies (Heliotropium curassavicum and Suaeda fruticosa, followed by a disturbed habitat
T. MEHMOOD & M. Z. IQBAL 456
Tab
le 2
.Im
port
ance
Val
ue I
ndic
es o
f spe
cies
in s
tand
s in
whi
ch s
peci
es o
ccur
red
as a
lead
ing
dom
inan
t
No.
of
stan
din
whi
ch s
peci
esis
lead
ing
Sua
eda
Tam
arix
Sal
sola
Cre
ssa
Atr
iple
xH
alox
ylon
Indi
gofe
raP
roso
pis
Che
nopo
dium
dom
inan
tS
peci
esfr
utic
osa
indi
caim
bric
ata
cret
ica
griffi
thii
recu
rvum
hoch
stet
teri
julifl
ora
albu
m
4S
. fr
utic
osa
104·
6057
·31
—86
·855
·0—
—62
·0—
4T.
indi
ca59
·32
98·3
162
·0—
48·8
52·3
——
—3
S.
imbr
icat
a50
·054
·01
93·8
——
——
53·1
—2
C.
cret
ica
53·3
4—
—89
·2—
——
——
2A
. gr
iffith
ii—
——
—85
·5—
—67
·05
65·6
12
H.
recu
rvum
53·2
353
·60
—39
·28
—84
·0—
—52
·12
1I.
hoc
hste
tteri
—43
·60
——
59·2
9—
82·8
3—
—1
P. ju
liflor
a—
——
——
——
81·6
5—
1C
. al
bum
—64
·99
——
——
——
72·2
4
PLANTS AND CHEMICAL WASTE 457
Tab
le 3
.C
orre
latio
n of
soi
l cha
ract
eris
tics
with
pla
nt c
omm
uniti
es
III
III
IVV
VI
VII
VII
IIX
Suae
daTa
mar
ixSa
lsola
Cre
ssa
Atr
iple
xH
alox
ylon
Indi
gofe
raP
rosp
isC
heno
podi
umC
omm
unity
Com
mun
ityC
omm
unity
Com
mun
ityC
omm
unity
Com
mun
ityC
omm
unity
Com
mun
ityC
omm
unity
Num
ber
of s
tand
sE
daph
icva
riab
les
5,9,
11,1
41,
2,7,
1910
,13,
203,
84,
166,
1812
1715
Soil
text
ure
Sand
y lo
amSa
ndy
loam
Sand
y lo
amSa
ndy
loam
Sand
y cl
aySa
ndy
loam
Sand
y si
ltySa
ndy
silty
Sand
y lo
amlo
amlo
amlo
amM
ax. w
ater
-20
·62
18·7
321
·37
24·4
526
·63
1616
·34
15·2
027
·84
hold
ing
(17·
25–2
3·44
)*(1
4·42
–22·
97)*
(15·
46–3
0·46
)*(2
2·48
–26·
43)*
(18·
94–3
4·33
)*(1
3·55
–18·
46)*
capa
city
(%
)pH
7·8
7·9
7·6
6·7
7·4
8·2
8·2
6·8
8·4
(7·3
–8·3
)(7
·6–8
·2)
(6·5
–8·6
)(6
·6–6
·9)
(6·7
–8)
(7·8
–8·5
)C
aCO
3(%
)22
·03
25·0
623
·16
19·2
521
·33
26·4
28·3
326
17·3
3(1
8·95
–27·
94)
(17·
70–3
0·33
)(1
8·60
–26·
55)
(18–
20·5
0)(1
6·72
–25·
95)
(23·
25–2
9·55
)O
rgan
ic4·
073·
774·
285·
754·
713·
254·
382·
595·
46m
atte
r (%
)(2
·70–
5·30
)(1
·85–
4·68
)(2
–6·9
5)(5
–6·5
)(3
·48–
5·95
)(2
·6–3
·9)
Inor
gani
c 43
4931
4951
2340
2520
phos
phor
us(3
1–53
)(1
7–78
)(1
5–42
)(4
4–53
)(4
9–52
)(1
1–35
)(p
.p.m
.)E
xcha
ngea
ble
2300
2475
2250
1808
1967
2650
2525
1650
2950
sodi
um (
p.p.
m.)
(193
3–27
00)
(188
3)–3
100)
(180
0–29
17)
(158
3–20
33)
(168
3-22
50)
(223
3–30
67)
Exc
hang
eabl
e15
7115
9215
3920
3418
1714
7518
3311
0019
50po
tass
ium
(1
200–
2100
)(1
367–
2000
)(1
033–
2050
)(1
900–
2167
)(1
633–
2000
)(1
417–
1533
)(p
.p.m
.)
*Min
imum
and
max
imum
ran
ge.
T. MEHMOOD & M. Z. IQBAL 458
species (Fagonia indica). Their luxurious growth indicated better soil conditions, suchas a sandy soil texture with good water-holding capacity (24·45%), slightly acidic pH(6·7) and moderate percentage of CaCO3
– (19·25%). Organic matter was fairly high(5·75%) with sufficient concentration of inorganic phosphorus (49 p.p.m.). The soilalso contained a lower concentration of sodium (1808 p.p.m.) as compared to theprevious communities. However, the exchangeable potassium was higher (2034p.p.m.).
5. Atriplex community. Atriplex griffithii was strongly associated with halophyticspecies (Chenopodium album and Mollugo lotioides) and disturbed habitat species(Prosopis juliflora) on sandy clay soil with good water-holding capacity (26·63%). Thesoil organic matter (4·71%) was moderate, inorganic phosphorus (51 p.p.m.) high, soilpH 7·4, with considerably high amounts of CaCO3
– (21·23%). The sodium (1967p.p.m.) and potassium (1817 p.p.m.) concentration were adequate.
6. Haloxylon community. Haloxylon recurvum was associated with different specieson a sandy loam soil with rather low water-holding capacity (16%). The soil pH (8·2)was high with high soil CaCO3
– (26·4%). Organic matter (3·25%) and inorganicphosphorus (23 p.p.m.) were low. The concentration of sodium (2650 p.p.m.) wasconsiderably high compared with potassium (1475 p.p.m.).
7. Indigofera community. Indigofera hochstetteri showed association with Atriplexgriffithiii, Tamarix indica and Mollugo lotioides on a sandy silty loam soil with low water-holding capacity (16·34%). Organic matter (4·38%) was high, inorganic phosphorus(40 p.p.m.) low, pH highly alkaline (8·2) with ample amount of CaCO3
– (28·33%).The concentration of sodium was higher (2525 p.p.m.) than potassium (1833p.p.m.).
8. Prosopis community. Prosopis juliflora was mainly associated with the halophyticspecies, Aeluropus lagopoides and disturbed habitat species, Senna holosericea. The soilswere a sandy silt loam, pH slightly acidic (6·8) and with low water-holding capacity(15·20%). The organic matter (2·59%) was fairly low and concentration of inorganicphosphorus (25 p.p.m.) also low; the CaCO3
– (26%) was high, with moderate sodium(1650 p.p.m.) and low potassium (1100 p.p.m.).
9. Chenopodium community. This community was found on sandy loam soils, withhigh water-holding capacity (27·84%), soil pH highly alkaline (8·4) with moderatepercentage of CaCO3
– (17·33%); it also contained high organic matter (5·46%) withlow inorganic phosphorus (20 p.p.m.). However, the amount of sodium (2950 p.p.m.)and potassium (1950 p.p.m.) were quite high compared with the communitiespreviously described.
Correlation of dominant species with soil characteristics
The dominant species of the study area showed significant correlation with soilcharacteristics (Table 4).
Tamarix indica was found to be dominant in 10 stands on sandy loam soils withmoderate water-holding capacity (18·79%), highly alkaline soil pH (8·1), sufficientCaCO3
– (24·61%), high concentrations of sodium (2609 p.p.m.) and low concentra-tions of potassium (1597 p.p.m.). Suaeda fruticosa showed dominance in eight standson sandy loam soils with moderate water-holding capacity (18·98%), with alkaline pH(7·9), sufficient CaCO3
– (24·38%), low organic matter (3·75%), sodium (2504p.p.m.) and low potassium (1581 p.p.m.). Haloxylon recurvum occurred in three standsas dominant species, preferentially on the sandy loam soils of low water-holding
PLANTS AND CHEMICAL WASTE 459
Tab
le 4
.C
orre
latio
n of
dom
inan
t spe
cies
with
soi
l cha
ract
eris
tics
No.
of
stan
ds
Exc
han
geab
lein
whi
ch s
pp.
Cal
ciu
mO
rgan
icIn
orga
nic
Dom
inan
tsh
owin
g 1s
t.Im
port
ance
Soi
lM
WH
Cca
rbon
ate
mat
ter
phos
phor
us
Sod
ium
Pot
assi
um
spec
ies
thre
e po
siti
onva
lue
text
ure
(%)
pH(%
)(%
)(p
.p.m
.)(p
.p.m
.)(p
.p.m
.)
1.Ta
mar
ix in
dica
10*2
1·25
**S
.L.*
*18·
79*
*8·1
**2
4·61
**3
·87*
*35*
*260
9**1
597*
2.S
uaed
a fr
utic
osa
822
·89
S.L
.18
·98
7·9
24·3
83·
7538
2504
1581
3.A
trip
lex
griffi
thii
619
·90
S.L
.20
·78
7·9
24·5
44·
0940
2471
1628
4.S
also
la im
bric
ata
521
·86
S.L
.21
·35
7·6
22·1
44·
3944
2147
1597
5.P
roso
pis
julifl
ora
521
·71
S.S
.L.
23·6
97·
222
·13
4·75
4119
4016
206.
Cre
ssa
cret
ica
422
·53
S.L
.21
·98
7·1
20·1
74·
5246
1946
1684
7.C
heno
podi
umal
bum
321
·10
S.L
.21
·74
8·1
22·1
14·
2836
2478
1789
8.M
ollu
go lo
tioid
es3
20·5
4S
.L.
20·8
27·
620
·80
3·62
5120
2215
399.
Hal
oxyl
on r
ecur
vum
319
·82
S.L
.16
·61
8·1
27·7
13·
5334
2706
1528
10.
Hel
iotr
opiu
m3
17·4
2S
.L.
23·8
57·
619
·75
5·05
3823
2820
72cu
rass
avic
um11
.A
elur
opus
316
·90
S.L
.16
·44
7·5
26·0
72·
8940
2283
1489
lago
poid
es12
.In
digo
fera
127
·61
S.S
.L.
16·3
48·
228
·33
3·90
3720
3320
50ho
chst
ette
ri13
.S
enna
122
·69
S.S
.L.
15·2
06·
825
·99
2·39
2516
5011
00ho
lose
rice
a14
.C
appa
ris
deci
dua
118
·53
S.L
.26
·43
6·6
18·0
06·
5044
1583
1900
15.
Innu
la g
rant
ioid
es1
18·3
0S
.C.L
.34
·33
6·7
16·7
25·
9449
1683
1633
16.
Fago
nia
indi
ca1
14·8
4S
.L.
26·4
36·
618
·00
6·50
4415
8319
0017
.Z
ygop
hyllu
m1
12·2
3S
.L.
18·2
07·
724
·33
4·28
3624
7817
89si
mpl
ex18
.H
ibis
cus
scin
dicu
s1
11·6
5S
.S.L
.30
·46
6·5
18·6
06·
9542
1800
1533
MW
HC
: Max
imu
m w
ater
-hol
din
g ca
paci
ty. S
.L.:
San
dy
loam
, S.S
.L.:
San
dy
silt
y lo
am; S
.C.L
.: S
and
y cl
ay lo
am.
* A
vera
ge v
alu
es f
or s
tan
ds.
T. MEHMOOD & M. Z. IQBAL 460
capacity (16·61%), high pH (8·1) and considerably high amounts of CaCO3–
(27·71%); it also had fairly high sodium (2706 p.p.m.) and low potassium (1528p.p.m.). Chenopodium album and Heliotropium curassavicum were dominant in threestands and exhibited strong association with soil characteristics, in particular withwater-holding capacity, pH, CaCO3
–, organic matter and sodium.Indigofera hochstetteri, Senna holosericea and Zygophyllum simplex were found on soils
with moderate water-holding capacity, acidic to basic soil pH, adequate CaCO3–, low
organic matter and low inorganic phosphorus. Indigofera hochstetteri and Zygophyllumsimplex soils exhibited sufficient concentration of sodium and potassium but soil withSenna holosericea had low concentrations of sodium and potassium.
Soil with Capparis decidua, Innula grantioides, Fagonia indica and Hibiscus scindicusshowed slightly acidic pH, moderate water-holding capacity, high organic matter andinorganic phosphorus but with low concentrations of sodium compared withpotassium, except Hibiscus scindicus soils which showed a higher concentration ofsodium as compared to potassium.
Discussion
Vegetation directly depends on the soil characteristics and conditions necessary fortheir successful growth and distribution. The distribution of species significantlyassociated with water-holding capacity of soil, pH, organic matter, inorganicphosphorus, calcium carbonate, exchangeable sodium and potassium, and increase ordecrease in these soil characteristics produced a significant impact on the speciesdistribution pattern.
The effects of chemical waste were analysed and an assessment was made of theirecological impact on soil and vegetation which appeared to be largely affected by thewaste effluents and subject to the halophytic and disturbed type of vegetation.
In most of the plant communities, the soil texture was a sandy loam with halophyticspecies such as Tamarix indica, Suaeda fruticosa, Salsola imbricata, Chenopodium album,Haloxylon recurvum and Atriplex griffithii. In the sandy-loam soil, the surface was loosetextured and the root system of the halophytic species could penetrate deeply into soiland extract water from the lower soil horizons for their growth during dry season. Soiltexture and water-holding capacity showed marked correlation and influenced thedistribution of species (Table 4). In clay loam soils there are more aggregate surfacesto accommodate films, more angles and more colloidal materials than in sandy soil;therefore, the available water of the clay loam soil was increased.
The degree and rate of incorporation of organic matter into the soil variesconsiderably, depending upon the climate and vegetation of the area. Wherevegetation growth was poor due to the accumulation of waste material, organic matterwas usually less. But, in those communities which had a higher percentage of soilorganic matter, the water-holding capacity of soil was consequently increased due tothe colloidal nature of the organic matter (Singh, 1986).
Plants are sensitive to the acidity or alkalinity of a soil. Extreme pH in the soil affectsthe concentration of different nutrients in the soil solution and makes them lessavailable to plants. However, many soil nutrients are soluble when present in neutralor near neutral solution (pH 6·5–7·2) (Tivy, 1982) and become available to the plants(Tables 3 and 4).
The CaCO3– was widely distributed in soil of the study area and had significant
impact on the distribution of species. The distribution of Indigofera hochstetteri,Haloxylon recurvum, Tamarix indica and Suaeda fruticosa were favoured by an excess ofCaCO3
– (Table 4). Those species which had higher amount of calcium carbonate inthe soil exhibited high species diversity and cover, because the soil CaCO3
– was not
PLANTS AND CHEMICAL WASTE 461
only antithetic in regard to soil chemistry but also increased the biological activity ofthe soil (Fitzpatrick, 1983).
The soil contained an excess of exchangeable sodium due to low rainfall andinsufficient leaching. Therefore, soluble sodium and other soluble salts produced asignificant impact on the plant communities (Tivy, 1982). The marked influence ofexchangeable sodium and potassium on the overall physical and chemical properties ofthe soil was associated principally with the behaviour of the clay and organic matter inwhich most of the cation-exchange capacity was concentrated. Tables 3 and 4 alsoshow that excess of sodium in the soil has profoundly favoured the frequentdistribution of halophytic species.
Salsola imbricata, Tamarix indica and Suaeda fruticosa exhibited frequent distributionon the polluted soil and showed a reddish brown colour which was due to waterdeficiency and high salt concentration. Photosynthetic activity of the species decreasedand production of anthocyanin pigments increased, giving rise to the reddish browncolour of the halophytic species in many of the plant communities.
References
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T. MEHMOOD & M. Z. IQBAL 462