Above ground standing phytomass of some grass-dominated communities ofKarachi [Pakistan]: winter aspect

Some 78 species (23 grasses, 2 sedges and 53 dicotyledons including 9 legumes) were seento compose winter aspect growth of 14 grass-dominated communities of Karachi, Pakistan. Themean number of species per site was 10.71 plus minus 1.25 (range: 3 - 20, CV= 44.1%). Sixty-one species occurred in one or two sites only. Cenchrus setigerus, C pennisetiformis,Dichanthium. annulatum, Sporobolus arabicus, Cynodon dactylon and Tephrosia strigosa wererelatively more frequently occurring species. Legumes were present invariably in all sitesexcept Urochondra setulosa and Sporobolus havolus dominated communities. The number ofspecies per site varied with the species dominating the site and the salinity status of thesite. Halophytic communities were composed of lesser number of species as compared to theglycophytic communities. The aboveground standing phytomass (AGSP) varied from 37.6 g-2 forone of the Cyanodon dactylon community to 694.0 g-2 for Desmostachya bipinnata dominatedsite. Litter related with AGSP positively (r = + 0.5577; p less then 0.01) as Litter (g-2) = 15.37+ 0.0657 AGSP (g-2) plus minus 18.96. Percent proportion of legumes biomass (PPLB) relatedinversely with proportion of grasses' biomass (r = - 0.5757; p less then 0.03) as PPLB = 39.483- 0.4088 PPGB plus minus 7.362. The communities in hand, with respect to their AGSP, werefound to have an order: D. bipinnata greater then U. setulosa greater then D. scindicumgreater then S. arabicus greater then C. dactylon = S. halvolus greater then D. annulatumgreater then C. pennisetiformis = C. aucherii = C. setigerus greater then S. verticillata. AGSPof waterlogged and semi-moist halophytic sites was substantially higher than that of dryglycophytic sites. The biomass distribution amongst the constituent species of each site wasgeometric. Edaphic characteristics of these communities have also been described.