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Inventorying of coastal and distribution of plant communities along Coast - I: Hawks Bay to Sandspit Beach

Item Type article

Authors Imran, Muhammad; Khatoon, Surayya; Ali, Qadeer Mohammad; Zaidi, Sahar; Khan, Aisha

Download date 04/10/2021 10:51:50

Link to Item http://hdl.handle.net/1834/40763 Journal of Marine Sciences, Vol. 20(1&2), 43-54, 2011.

INVENTORYING OF COASTAL PLANT SPECIES AND DISTRIBUTION OF PLANT COMMUNITIES ALONG KARACHI COAST - I: HAWKS BAY TO SANDSPIT BEACH

Muhammad Imran, Surayya Khatoon, Qadeer, Mohammad Ali, Sahar Zaidi, Aisha Khan Department of Botany, , Karachi – 75270, Pakistan (MI, SK, AK). Marine Reference Collection and Resource Center (MRCC), University of Karachi, Karachi –75270, Pakistan (QMA). Department of Botany, Federal University of Arts, Science, and Technology, Karachi, Pakistan (SZ). email: [email protected]

ABSTRACT: The flora and vegetation of about 4.5km coastal stretch from the Sandspit Beach to Hawke’s Bay Beach was yearly studied from 2005 to 2009. A total of 71 species was recorded belonging to 21 dicots and two monocots families. The vegetation was mostly halophytic and xerophytic with the exception of some annual species. The overall dominant species was marina ; however the study area had different microhabitats and each had its own dominant species. While the forest in the Backwaters lagoon appeared to be comparatively in good shape, the sea-front vegetation was found much damaged. The important sand-binding species like Ipomoea pes-caprae and Halopyrum mucronatum appeared only sparingly, while the endemic species Asparagus dumosus totally disappeared from the area in recent years. The apparent reason for this damage is human activity like the construction of huts and visitation of these beaches by a large number of picnickers from the city. The destruction of vegetation results in the collapse of ecosystem. The fauna dependant on vegetation also disappears and the ecological services of the ecosystem come to a halt.

KEYWORDS: Coastal flora and vegetation, halophytes, coastal lagoon, microhabitats, , anthropogenic disturbance.

INTRODUCTION

Sandy coastal deposits are found on shores all over the world, from polar latitudes to tropics (Araujo & Pereira, 2004). The forces that create, mold and destroy these deposits are basically wind, sea level oscillations and the presence or absence of vegetation (Martinez & Pusty, 2004). Coast in some cases is an elongated barrier, narrow beach and systems, which may shelter lagoons, mangroves and salt marshes from direct wave and wind action (Nordstorn, 2000). The stress factors steeply gradate from the sea to inland, each stress factor declining with increasing distance from the beach, and may be summarized as salt spray, and blast, sand burial, episodic over wash, nutrient deficiency, high temperature, drought, and high winds (Barbour, 1992). When the barriers and spits are formed, a new empty habitat becomes available to vegetational succession processes which impose a regular progression of vegetal forms, with typical of each successional stage presenting different strategies for habitat occupation, fitted to the disturbance degree and to the resource availability of these 44 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011. habitats (Barbour et al. 1987; Bazzaz, 1996). The evolution of plant community structure of different ages along the spit, and also along the gradients seaward to landward, may help us to understand how the plants deal with the different degrees of stress and disturbance, providing useful insights to identify the mean level of disturbance of a habitat, and also to select best group of species to restore with different degrees of anthropogenic disturbances (Emilio et al. 2004). The coastal ecosystems all over the world are threatened due to human population pressure and many other factors (Arauja and Pereira 2004). Any recent work about the plant biodiversity of Karachi Coast is not available. The first floristic work on plants of Karachi was the Flora of Karachi by Jafri (1966). The Flora mentioned 70 species from coastal areas of Karachi. Hussain (1970) analyzed coastal sand dunes around Karachi and recognized 17 plant associations. Khan (1987) did phytosociological survey of the entire coast of Pakistan and recorded a total of 233 species. However it is not clear that how many species were recorded from Karachi Coast. Besides this, a lot of habitat destruction and modification has occurred over all these years due to anthropogenic activities which must have translated into biodiversity changes. Certain comparatively recent works have focused on selected plant groups like mangroves (Saifullah et al. 1994), marine algae (Chaudhari, 1961; Salim, 2009), and certain species of halophytes and their germination (Aziz et al. 1996; Gul & Khan, 1998; Gulzar et al. 2001; Khan et al. 2003). However, any comprehensive documentation of flora ad vegetation of Karachi coast is not available.

The Coast: The coast of Pakistan along the Arabian Sea extends from Sir Creek in the southeast to the Gavatar Bay in the west along Pakistan- border. The coast is shared by the province of in southeast and the Balochistan province in west. The Sindh coast consists of the Indus delta and Karachi coast. Lying southeast to Karachi the upper margin of Indus delta lies just south of Karachi Division’s boundary. The coast of Karachi Division extends from in the east to Hub River estuary in the west. In contrast to the Indus delta which all consists of mud flats and tidal creeks, the coast of Karachi is quite heterogeneous consisting of sandy beaches, rocky shores, and mud flats with mangrove vegetation. Two small seasonal rivers traverse the city. The Malir River has its estuary in the Gizri creek where small mudflats and mangroves are present; while the Lyari River opens into a lagoon commonly known as Karachi western backwaters. Here comparatively vast mudflats with rich mangrove vegetation are present. Although Lyari and Malir Rivers bring city’s sewage and industrial effluents for most part of the year, but in case of heavy monsoon rains they carry substantial amounts of freshwater. The western part of Karachi coast from Paradise Point to Cape Monze bears low hills and sandy rocky shores. The length of Karachi coast has been variously mentioned as 60km (http:// www.findpk.com/cities/html/karachi.html), 90 km (Rizvi et al. 1995), and 100 km (Majeed et al . 2010), probably depending upon the way of measurements. A distinctive feature of Karachi coast is a 12.5 km long sand spit extending from the Manora Island to Hawk’s Bay in the northwest direction. This 100-200m wide (Durranee et al. 2008) sand spit encloses the lagoon known as Karachi Western Backwaters. The sandy beaches along its seaward margin have three major picnic points namely the Manora Beach, the Imran et al.: Inventorying of coastal plant species 45

Sandspit Beach, and the Hawk’s Bay Beach. A metalled road passes through this strip while a number of huts for picnickers are built from Sandspit Beach to the Hawk’s Bay beach. A large number of people visit these beaches therefore there is a high degree of anthropogenic disturbance. On the other hand, the mangrove forest in the lagoon is an important wintering ground for migratory birds as well as rich habitat for many residential birds; while the Sandspit Beach is an important site for marine turtles’ nesting (Durranee et al. 2008).

The Study Area: The present study covered about 4.5km long part of the sand spit from the Sandspit Beach to the Hawk’s Bay Beach and about 2.5km part along the landwards margin of the lagoon. The climate all over Karachi coast is hot and arid, with an average annual rainfall of 220mm (Majeed et al. 2010). Summer maximum temperatures range from 30˚C to 45˚C, while winter minimum temperatures usually range from 6˚C to 18˚C. Though the rainfall is scanty, but due to high relative humidity in the atmosphere (up to 90% in winter’s early mornings) there is an ample dew formation from November through all winter up to early spring.

MATERIALS & METHODS

In the present study, the above mentioned part of Karachi coast was visited periodically during the years 2005 – 2009. All the plants were listed and identified with the help of Flora of Pakistan (Ali & Nasir, 1989-1991, Ali & Qaiser, 1992-1998, Ali & Qaiser, 2000-2010) and Flora of Karachi (Jafri, 1966). Sampling was done by random quadrats method (Curtis and McIntosh, 1950) at 12 spots 0.5km apart from each other. Five quadrats of 2x2m were laid at each spot. Sampling was done both on the sand spit and the land wards side of the lagoon 2.5km along the road from the main sea front.

RESULTS & DISCUSSION

The vegetation along the coast consists of a mixture of species with certain species being more dominant along some parts of the coast according to microhabitat conditions. A total of 71 species of plants were recorded with 37 , 30 herbs and four species of trees. The complete list of plant species with their life forms is given in Table.1. Among the total number of 71 species in the study area (Hawks Bay to Sandspit) only six species i.e., Avicennia marina, belangerana, macrostachyum, , Haloxylon recurvum, and Aerva javanica; showed frequency of occurrence higher than 20% (Table.2). The natural succession process of dune formation and their maturation by the establishment of particular kind of plant species has been obliterated in the study area due to the construction of road, huts, and constant human activities. Nevertheless, certain microhabitats could be identified which had their own particular species. The huts along the beach are constructed just above the high tide mark, and the road passes a few meters behind the huts. At the Sandspit Beach, the WWF-P Wetland Center is also present amid the mangrove forest. The road runs along the lagoon margin. Behind the huts and in 46 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011.

. forms and Habit - of plant species with their life 1. List Table

Imran et al.: Inventorying of coastal plant species 47

(Continued....)

. forms and Habit - 1. ofList plant species with their life Table

48 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011.

. (Continued....) forms and Habit - 1. ofList plant species with their life Table

Imran et al.: Inventorying of coastal plant species 49

. (Continued....) forms and Habit - with their life 1. ofList plant species Table

50 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011.

Table 2. Phytosociological attributes of the vegetation at Karachi Coast.

Plant Names RF 1 RC 2 RD 3 IVI 4 Aerva javanica 35.48 14.12 16.25 21.95 Arthrocnemum macrostachyum 30.43 07.62 14.06 17.37 Atriplex stocksii 21.43 13.56 14.58 16.52 Avicennica marina 52.94 63.26 66.00 60.04 Halopyrum mucronatum 12.00 10.00 10.00 11.00 Halostachys belangerana 69.57 92.38 85.94 82.63 Haloxylon recurvum 21.43 13.56 14.58 16.52 Heliotropium bacciferum 08.00 19.00 14.00 13.98 Indigofera oblongifolia 17.00 09.77 08.75 11.79 Limonium stocksii 05.53 07.17 07.50 06.37 Polycarpaea spicata 03.00 06.00 02.00 03.04 Senna italica 08.00 20.00 14.00 14.01 virginicus 12.00 10.00 10.00 11.00 Suaeda fruticosa 47.05 36.74 35.01 39.60 1=Relative frequency, 2=Relative cover, 3=Relative density and 4=Importance value index between them some low sand dunes can be seen, while some areas along the road are more or less flat. In such flat areas patches of sandy loam were present, while other areas mostly had sand and gravel. As the whole study area is arid and saline, almost all the recorded species were xerophytes and halophytes. However, in the years of sufficient rainfall, the patches of sandy-loam supported certain non-halophytic annual species after the rainy season, such as Indigofera cordifolia, Indigofera hochstettri, Tephrosia strigosa, Heliotropium strigosum, Digera muricata, Cleome viscosa, etc. Above the high tide mark on the dunes, Ipomoea pes-caprae, Halopyrum mucronatum, , Heliotropium bacciferum, etc. were observed. Larger species like Tamarix alii, Indigofera oblongifolia, Aerva javanica, etc. were found on slightly larger dunes. Roadside surface was mostly flat on which Indigofera argentea, Lotus garcinii, Polycarpea spicata, Launaea residifolia, Zygophyllum simplex, Cressa cretica, Cyperus arenarius, Urochondra setulosa, Panicum turgidum, etc. were found. Along the margin of lagoon from where the silt deposition started, dense vegetation consisting of Arthrocnemum macrostachyum, Halostachys belangerana, imbricata, Suaeda fruticosa, Salvadora persica, Aerva javanica, etc. was seen. In wetter places, grass species Aeluropus lagopoides and Sporobolus virginicus were present. The mud flats in the lagoon had almost pure population of the mangrove species Avicennia marina. Imran et al.: Inventorying of coastal plant species 51

Along the landward margin of lagoon, almost pure populations of Halostachys belangerana, Arthrocnemum macrostachyum, Suaeda fruticosa, and Urochondra setulosa formed scrub vegetation. Few grass species like Panicum turgidum and Sporobolus arabicus were found associated. The raised dry sandy/rocky land away from lagoon had species like Euphorbia caducifolia, Cappars cartilaginea, Fagonia indica, Tribulus terrestris, etc. Vicinities of some cultivated areas near the Wetland Center and other buildings had their own typical species which were neither xerophytes nor generally halophytes. Complete list of all species is provided in Table-1 and complete lists of species of each microhabitat are given in the Appendix-I. Although several species occurred in more than one kind of microhabitats, but their frequency was greater in any one particular type of microhabitat.

Species of Concern: The endemic species Asparagus dumosus has a limited distribution in the coastal areas of Sindh and Balochistan (Stewart 1972). Until early 1990s, large bushes of this species were found on dunes above the high tide mark at Hawke’s Bay Beach (Personal observation, S.K.). However, in the present study it was not found anywhere. On the other hand, the alien invasive species Prosopis juliflora was present in every kind of microhabitat, even in the intertidal mudflats among the mangroves.

Conclusion: Looking at the overall study area, the mangrove species Avicennia marina was the dominant species. However, it was mainly found within the lagoon on intertidal mudflats. Different kinds of microhabitats had their own dominant species. The vegetation of the main sea front was however in much damaged condition. Ipomoea pes- caprae which is the pantropical beach species (Araujo & Pereira, 2004) forming vast continuous cover on sand thus reducing erosion, was found here only in small patches. Similarly Halopyrum mucronatum, another sand-binding species was also sparingly present. The endemic species Asparagus dumosus, also an excellent soil-binder due to being rhizomatous, totally disappeared. It probably fell prey to the developmental activities like the construction of huts. The coastal vegetation not only adds to the serenity of the coast but also has important ecological functions like the control of erosion and stabilization of sand dunes. Birds and other natural fauna find food and shelter in the natural vegetation, wherever it is, serves as carbon sink and liberates oxygen (Prasetya 2006) therefore contributes in controlling the global warming.

Appendix-I Species lists of different microhabitats in the Study area:

i) Low to a little higher dunes above iv) Lagoon margin along mainland: the high tide mark: 1. Arthrocnemum macrostachyum 1. Aerva javanica 2. Halostachys belangerana 2. Calotropis procera 3. Suaeda fruticosa 3. Heliotropium bacciferum 4. Urochondra setulosa 4. Atriplex stocksii 5. Aeluropus lagopoides 5. Cressa cretica 6. Panicum turgidum 52 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011.

6. Ipomoea pes-caprae 7. Sporobolus arabicus 7. Prosopis juliflora 8. Indigofera oblongifolia v) Intertidal mudflats in lagoon: 9. Tamarix alii 1. Avicennia marina 10. Aeluropus lagopoides 2. Arthrocnemum indicum 11. Halopyrum mucronatum 3. Prosopis juliflora 12. Panicum turgidum 4. Aeluropus lagopoides 5. Sporobolus virginicus ii) Flat land along roadside beyond high tide mark (including sandy- vi) Raised dry sandy-rocky land away loam patches): from lagoon: 1. Aizoon canariense 1. Aerva javanica 2. Aerva javanica 2. Calotropis procera 3. Digera muricata 3. Helitropium crispum 4. Calotropis procera 4. Heliotropium ophioglossum 5. Launeae resedifolia 5. Heliotropium strigosum 6. Heliotropium strigosum 6. Senna holosericea 7. Senna italica 7. Senna italica 8. Cleome viscosa 8. Capparis cartilaginea 9. Polycarpaea spicata 9. Cleome brachycarpa 10. Atriplex stocksii 10. Cleome viscosa 11. Cressa cretica 11. Convolvulus glomeratus 12. Sida ovate 12. Euphorbia caducifolia 13. Prosopis juliflora 13. Euphorbia clakeana 14. Glinus lotoides 14. Abutilon fruticosum 15. Cistanche tubulosa 15. Abutilon indicum 16. Astragalus fatmensis 16. Sida ovata 17. Indigofera argentea 17. Prosopis juliflora 18. Indigofera cordifolia 18. Tephrosia uniflora 19. Indigofera hochstetteri 19. Fagonia indica 20. Indigofera oblongifolia 20. Tribulus terrestris 21. Tephrosia strigosa 21. Leptotherium senegalensis 22. Lotus garcinii 23. Heliotropium curassavicum vii) Vicinity of cultivated places 24. Limonium stocksii and buildings: 25. Zygophyllum simplex 1. Alternanthera sessilis 26. Cyperus arenarius 2. Amaranthus graecizans 27. Cyperus bulbosus 3. Digera muricata 28. Cyperus conglomerates 4. Launaea procumbens 29. Panicum turgidum 5. Chenopodium murale 6. Euphorbia clakeana iii) Lagoon margin 7. Euphorbia hirta along sand spit: 8. Euphorbia serpens 1. Aerva javanica 9. Cyperus longus 2. Arthrocnemum macrostachyum 10. Cyperus rotundus Imran et al.: Inventorying of coastal plant species 53

3. Salsola imbricata 11. Cynodon dactylon 4. Suaeda fruticosa 12. Dactyloctenium aegyptium 5. Prosopis juliflora 13. Dactyloctenium areistatum 6. Halostachys belangerana 14. Eragrostis ciliaris 7. Aeluropus lagopoides 15. Setaria verticillata 8. Urochondra setulosa 9. Sporobolus virginicus

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