Abstract: Calamagrostis angustifolia is the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain.The study on its biomass structure and the N and P contents in its different organs showed that the biomass of different C.angustifolia organs in the two types of wetland communities was distinctly different,which could be described by Y=A+B_1t+B_2t2+B_3t3.The biomass of aboveground part and each organ presented single peak changing,with the maximum value of the latter occurred 15 d after.The F/C values were all less than 1,which was bigger in typical meadow than in marsh meadow.The total N and P contents in different organs of aboveground part all descended linearly in growth season,with the order of leaf＞vagina＞stem.The total N content in the roots of two C.angustifolia types was consistent,while that of total P was quite different.The contents of total N,NH₄⁺-N and NO₃^--N,especially of NH₄⁺-N and NO₃^--N,varied widely in different organs,with NH₄⁺-N/NO₃^--N＞1.Root was the important storage of N and P,but the storage of N and P in stem,leaf and vagina fluctuated greatly.The N/P ratios of two C.angustifolia types were all less than 14,which implied that N might be the limiting nutrient of C.angustifolia,and the limitation degree was higher in typical meadow than in marsh meadow.

Key words: Tsuga longibracteata, Population, Life table, Survival curve