Seasonal dynamics of shoot nutrients in Schoenus ferrugineus (Cyperaceae)

Seasonal patterns of biomass and standing stock (g m⁻²) of nitrogen, phosphorus, potassium and calcium were documented in Schoenus ferrugineus L. from an annually mowed calcareous fen in southern Germany. The peak standing crop of nitrogen, phosphorus and potassium occurred in mid-July. Prior to the end of the growing season, 44% of total potassium, 34% of total phosphorus and 28% of total nitrogen were retranslocated out of the shoots, based on differential nutrient losses between covered and uncovered plots. There is no evidence that any calcium was retranslocated, but 24% of peak calcium and 13% of potassium was leached from standing dead shoots. More than half of the peak phosphorus was found in the overwintering green shootbases. In the light of the low availability of nutrients in the soil, retranslocation of phosphorus in particular is essential, if adequate internal nutrient levels are to be maintained, despite various proposed uptake mechanisms.