PHYTOSOCIOLOGICAL SURVEY OF PAKISTAN COAST WITH SPECIAL REFERENCE TO PASTURE AND FOREST DEVELOPMENT THROUGH BIOSALINE TECHNIQUE

Phytosociological survey of Pakistan coast was carried out with special reference to the development of pasture and forest utilizing underground saline water for irrigation. Besides descriptive and quantitative phytosociological studies. Experimental – ecophysiological approaches were also employed. Excluding mangroves 233 species of naturally growing plants (183 dicots + 49 monocots + 1 gymnosperm) were collected from the coastling comprising littoral salt marshes, coastal desert plains and coastal comprising littoral salt marshes, coastal vegetation were sampled and sampled and phytosociological data was analysed to obtain information related to compositional and structural characteristics with special emphasis on the community oxganization. The vegetation on the existing vegetational – envisonmental complex so as to facilitate the selection of economically valuable salt tolerant plants of fodder and fuel potential. The vegetation within the littoral salt marshes was related to the typical helo-catenas and exhibited extreme simplicity of structure and composition. It coastal desert plains the vegetation comprised a mosaic pattern of community types related to the habitat conditions of water resource, land forms, soil types, salinity and sodicity status and the successional stages of vegetation.The sedimentary mountain slopes and hills in Makran were generally absolutely barren due to intense erosion whereas the calcarious hills of Karachi and Lasbella had vegetation representing various successional stages. All the stands studied were simple in their structure and organization and exhibited geometric distribution of abundance among the constituent speciesLeading dominant analysis indicated the occurrence of 30 vegetational groupings. The ecological affinities among the leading dominants have been described. Objective classification, on the basis of 40% compositional similarity, delimited 35 discrete communities. These have been described in relation to their location, topography, structure and composition, distribution of life forms and leaf size classes and edaphic characteristicsCorrelation and regression analyses and the behavior of some selected species along classified salinity and sodicity gradients indicated that besides some 39 well known halophtic species, the plants such as Aerua pseudo-tomentosa, Calotropis procera, Heliotropium sublatum, Indigofera oblongifolia, Lycium depressum, Panicum turgidum, Salsola drummondii, Saccharum griffithii and Sporobolus arabicus could be ranked as salt tolerant to various extentGrazing status as signed to the taxa revaluated that sine species are grazed by animals to various extent. Among them 25 are the grasses, 14 are the legumes and 28 others belonging to diverse families. It appeared that Sporobolus arabicus, Panicum turgidum, Desmostachya bipinnata, Cyanodon dactylon, Anabasis setifera, Arthrocnemum indicum, Bienertia cycloptera, Salsola drummondii, Tamarix aphylla, Tamarix indica, Salvadora persica, Salvadora oleoides, Zygophyllum simplex, Prosopis cineraria, Acacia nilotica and Indigofera oblongifolia could be quite promising for fodder production on coastal sandy strata using saline water for irrigation. A number of phanerophytic taxa that could be important for saline afforestation are also indicatedStudies of grazable herbaceous communities that emerge during monsoon season appeared to have high percentage of therophytes followed by the chamaephytes. The grasses constituted the dominant component and the legumes were invariably present in all the sites studied. Among grasses, Sporobolus arabicus, Panicum turgidum, Pennisetum divisum, Cenchrus pennisetiformis and Desmostachya bipinnata are important. Amongst legumes, I oblongifolia emerged as major species with substantial phytomass in three communities of which two belonged to saline habitats (Sporobolus and Desmostachya – dominated communities respectively) and one associated with non-saline soil (Dichanthium communityPlantations of measquite (Prosopis juliflora (Swartz.) D.C.) raised by Baluchistan Forest Department to stop sand drift at coastal areas of Pakistan, Gwadar and Pasni using highly saline underground water depending upon the distance from the sea coast. In sites of compact native old alluvium, the water table was generally deeper. The EC of the water of the functional wells at these places varied from 7.0 to 21.0 dS.m-1Six-months-old seedlings transplanted at a distance of 2.0-2.5 m were each irrigated with 10-12 litters of water at weekly interval during the summer and fortnightly during winter for a 2 year period. Within 10 year growth period, the plant reached a height of 6.54+0.61 m with average canopy cover as large as 56.66+8.37 sq.m., and the diameter of stem, 18.74+1.84 cm. Dry wood productivity of these plantations varied depending upon the physiographic conditions and ranged from 2.18 to 3.28 m tons/ha/yr for the initial year of post-transport growth if planted at an inter-plant distance of 2.5m The quality of wood was tested and result indicated that though under high salinity regime, the productivity was substantially reduced, the quality of wood remained more or less unaffectedExperimental – ecophysiological approach was employed to examine the germination, growth and salt tolerance of some promising species of fodder (Panicum turgidum, Pennisetum divisum, Sporobolus arabicus and Indigofera oblongifolia) and fuel (Azadirachta indica and Prosopis juliflora) value. The fodder species were grown on coastal sand in drum pots being irrigated with amended sea water dilutions weekly. A cheap recipe of fertilizer – mixture was worked out for the amendments of various sea water dilutions in order to reduce Na+ toxicity and provide essential micronutrients. The multipurpose fuel wood tree, Azadirachta indica was grown in coastal field conditions of Bhawani (off Baluchistan coast) by irrigating with subsoil saline water. The experiment in each case was continued up to a period of one year. Prosopis juliflora was, however, tested in earthen pots at seedling stage only to mainly investigate its mechanism of salt tolerance. The fodder species tested, on the basis of total grazable biomass productivity, irrespective of their decreasing salt sensitivity, may be arranged as S. arabicus; P. turgidum, I. oblongifolia, P. divisum. Both the fuel species tested were also quite promising from bios line afforestation point of view. All the species attempted to avoid the toxic effects of excessive sodium through varied strategies. I. bolongifolia tended to develop succulence in leaves, P. turgidum, P. divisum, A. indica and P. juliflora tended to exclude Na+ to varied extent from leaves by retaining in roots and S. arabicus operated an excretory mechanismThe differences in salt tolerance of the experimental species appeared due to the differences in the magnitude of threshold concentrations of salts associated with the contents of protoplasm, ability to regulate ionic movement and the degree of the metabolic changes and the structural alterations associated with the salinity stress. The physiotypic variations with respect to salt tolerance of the species investigated are discussed in physiological context