A study of nutrient dynamics in the coastal dunes of northwestern egypt.
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Biomass and nutrient cycling are evaluated in sites of Ammophita arenaria and Onoaisvaginalis which are among the most common species growing on the coastal dunes of the western desert of Egypt. Both species accumulate N to higher levels than Ca, although growing on calcareous soil, and exhibit faster turnover rates. Uptake and accumulation of nutrients in different organs seem to be a function of phenology. The uptake rate is also affected by carbohydrate supply as an energy source for transport. Large quantities of N and K uptaken by Ammophila are retained in its perennating organs, while Ca exhibits a similar trend in Ononis. The mineralomass amounts to about 35 kg/ha for the former and about 40kg/ha for the latter species. The high concentration of nutrients in phytomass and necromass of both species compared to that in soil suggest that plants in deserts may represent the main bulk of the available nutrients. While the withdrawal of critical nutrients from dying parts of both species may reflect a conservation strategy for more efficient growth.