Abstract: An investigation was made on the contents, distribution patterns, and cycling characteristics of N, P and K in Scirpus mariqueter wetland ecosystem at the upper, middle, and lower Jiuduansha shoals of Yangtze River estuary. With the increasing altitude along the gradient lower shoal  middle shoal  upper shoal, the P and K contents in the whole soil profile decreased, while N content had less variation. The total N (TN) content in the soil profile was in the order of middle shoal > lower shoal > upper shoal, total P (TP) and total K (TK) contents were lower shoal > middle shoal > upper shoal, available N (AN) content was middle shoal > lower shoal > upper shoal, and available P (AP) and K (AK) contents were lower shoal > middle shoal > upper shoal. The contents of soil total and available N, P, and K were in the order of TK > TP > TN, and AK > AN > AP, respectively, and decreased with soil depth. N and K were more accumulated in surface soil, and the absorbed amounts of N and K by S. mariqueter at the three shoals were higher than that of P. The absorbed amount of soil nutrients by S. mariqueter at upper and lower shoals was in the order of K > N > P, and that at middle shoal was N > K > P. The S. mariqueter at upper shoal absorbed the highest amount of soil nutrients, followed by that at middle shoal, and at lower shoal. The absorption coefficient of nutrients in S. mariqueter wetland ecosystem at the three shoals was N > P > K, and cycling coefficient was K > N > P. The N at the upper shoal and the K at the middle and lower shoals had the highest utilization coefficient.

Key words: Desertification, Sandy grassland, Common plant population, Anti-oxidative enzymes