The variation in composition, structure, phytomass and net primary productivity was analyzed in a Dichanthium annulatum (Forssk.) Stapf. dominated coastal community of Karachi, Pakistan. Phyto-ecological parameters of vegetation were studied at monthly interval for a year. Only 10 species were encountered from the site. D. annulatum was the leading dominant throughout the year in association with Indigofera oblongifolia and Cyperus rotundus. The density of Dichanthium remained more or less unchanged throughout the year except slight increase in September. Other species such as Cyperus rotundus and Alysicarpus scariosus showed density peak in September. The relative abundance pattern of species was geometric throughout the year. The changes in the aboveground live plant biomass (LB), standing dead (SD), litter (L) and belowground biomass were studied. LB was maximum (422.4 g-2 ) in October and March (399.2 g -2 ). LB related positively with rainfall and soil moisture content. The effects of rainfall were better represented in the month subsequent to its occurrence and remained noticeable for not more than up to 50- 60 days. SD was maximum in November (358.4 g -2 ). Litter was minimum in September (50.6 g -2 ) and maximum in May (159.7 g -2 ). The below- ground biomass was larger than the aboveground biomass. Above- ground net primary productivity (ANP) as evaluated by various methods varied from 310 to 704 g -2 .year-1 (average = 496.1 ± 90.63 g -2 .year-1 ; CV = 36.5%). Belowground net produc- tivity (BNP) was 754 g -2 .year g -1 . Annual efficiency of energy capture by the primary producers was estimated to be 0.53% on the basis of half total solar radiation. Annual energy flow diagram through primary producer compartments is presented.
D. Khan. (2005) SEASONAL VARIATION IN STRUCTURE, COMPOSITION, PHYTOMASS AND NET PRIMARY PRODUCTIVITY IN A DICHANTHIUM ANNULATUM (FORSSK.) STAPF. DOMINATED COASTAL NON-SALINE SITE OF KARACHI, PAKISTAN, , Volume 2, Issue 2.
