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Pak. J. Bot., 41(6): 2883-2892, 2009.

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SEASONAL VARIATION IN PRODUCTIVITY OF CRESSA CRETICA  FROM COASTAL POPULATION ALONG THE ARABIAN SEA

FARHAT AGHA

Abstract: The productivity of Cressa cretica was studied for two years at monthly intervals in a coastal population located at Gizri Creek, south of Karachi, Pakistan. Cressa cretica showed variation in productivity in response to environmental factors. Net productivity and aboveground biomass were higher during the brief winter in comparison to summer which also varied between the two study years. Belowground biomass was much lower than the aboveground biomass but both followed similar seasonal trends. Increase in standing crop biomass and aboveground dead biomass also varied considerably. The highest net productivity in Cressa cretica was 0.18 g m^-2d^-1 in January. Electrical conductivity of shoots showed two peaks during the year 1997-1998 and gradually declined after October, while belowground parts showed little variation both within and between the years at around <10 dS m^-1 except for high values of 22 dS m^-1 in June 1997-98. Sodium was much higher followed by Cl^- and K⁺ while Ca⁺ and Mg²⁺ were very low. Similar ion patterns were found in roots. Cressa cretica could be a useful sand dune stabilizer along the coast which has potential for increased productivity under seawater irrigation.

DA Degree College for Women, Phase 7 (ext), Defense Housing Authority, Karachi-76000, Pakistan