C,N and P dynamics in above ground parts of Calamogrostis angustifola,which was growing on different water zones with various water regimes,were studied by field investigation.The results show that total carbon(TC) fluctuated with time in all zones and were higher in the zones inundated all year long.Total nitrogen(TN) and total phosphorus(TP) decreased with time and the increase of soil water.C,N,and P of the leaves were higher than that of stems and vaginas.The ratio of C and N differed in zones with various inundation periods,and the ratio of C and P increased with the growth of the plant and soil water contents.The ratio of N and P generally increased with soil water contents,while increased and then decreased in the growing season.The quality of Calamogrostis angustifola decreased with increasing soil water.At the early growing stage,the growth of the plant was limited by N under all water conditions,while at the later growing stage,P was the limiting factor at the zone inundated all year long and N remained the stressing factor in the other zones.