PJB-2000-24
SEASONAL VARIATION IN STRUCTURE, COMPOSITION, PHYTOMASS, AND NET PRIMARY PRODUCTIVITY IN A LASIURUS SCINDICUS HENR., AND CENCHRUS SETIGER US VAHL., DOMINATED DRY SANDY DESERT SITE OF KARACHI
D. KHAN, M. FAHEEMUDDIN, S.S. SHAUKAT* AND M.M. ALAM
Abstract
Variation in composition, strucrure, plant biomass and net primary productivity was analyzed in a grass dominated sandy desert community of Lasiurus scindicus Henr., and Cenchrus setigerus Vahl., situated within the campus of University of Karachi. Pakistan. Life form indicated a thero-hemi-cryptophytic/geophytic flora. Phytosociological parameters of vegetation were srudied at monthly interval from June 1990 to June 1991. The density as well as live biomass-based diversity of the community was generally low and dominance high. The live-biomass-based diversity varied seasonally and was the function of precipitation and soil moisture. On the advent of rain in August with the increase in diversity, the relative abundance pattern tended to approach log-normal distribution which was otherwise geometric. The density-based diversity declined after August rains largely due to very high density of Tragus roxburghii (1327 plants.m-2), a small graminoid, which created the condition of very high dominance concentration.
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