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

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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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Burnham, C.P. (1980). The soils of England and Wales. Field Studies, 5: 349–363.Dueck, T.A. & Endendijk, G.J. (1987). Soil pollution and changes in vegetation.Chemosphere,

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Jackson, M.L. (1958). Soil Chemical Analysis. Englewood Cliffs, NJ: Prentice-Hall. 498 pp.Keen, B.A. (1931). The Physical Properties of Soil. New York: Longman Green & Company. 380

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Tivy, J. (1982). Biography. A study of plants in the ecosphere (2nd Edn). New York: Longman. 397pp.

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T. MEHMOOD & M. Z. IQBAL 462