PLANT COLONIZATION AND BIOMASS PRODUCTION IN A XERIC TERRIORTHENT AMENDED WITH URBAN SOLID REFUSE

A long-term field experiment was conducted in a semiarid Mediterranean site to determine the effect of the application of several doses (6.5 , 13, 19.5 and 26 kg m(-2)) of urban solid refuse (USR) on the plant c olonization, plant cover and biomass production. The plant species ric hness did not increase in all the treated plots with respect to the co ntrol except immediately after the treatment was applied. This increas e was only maintained after three years in the lowest dose of USR and the control. The addition of USR slowed floristic change and the lowes t percentages of change corresponded to those plots receiving the high est doses. The plot receiving the lowest doses behaved in a similar wa y to the control plot. Plant cover increased substantially in the plot s treated with USR compared with the control plot, even the lowest dos es increasing the cover by 500 per cent. Plant biomass also significan tly increased in all the amended plots compared with the control, alth ough such increases were not directly proportional to the doses of USR added. USR can be considered an effective organic amendment to regene rate the plant cover of degraded soils. (C) 1997 John Wiley & Sons, Lt d.