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Seasonal changes in pool size, inflow rates in biomass and phosphorus, and the efficiency of phosphorus use in the stand of three populations (Helianthus tuberosus, Artemisia princeps and Phalaris arundinacca) in the basin of the Mt. Geumoh were investigated. During the early growing period, in the three species populations, the relative size of the phosphorus pool of population was larger than that of its biomass pool, but that of the phosphorus pool of belowground part decreased more rapidly than that of its biomass pool. In the A. princeps and P. arundinacea populations, the phosphorus inflow rate was markedly high during the soil thaw in early spring and its seasonal change pattern was different from that of the biomass production rate, showing two peaks in March and June. But in the H. tuberosus population, the two seasonal change patterns were alike. The annual biomass production was 2283 gDM m^-2 in the H. tuberosus, 1884 m^-2 in the A. princeps and 1879 gDM m^-2 in the P. arundinacea population, and the annual phosphorus inflow was 11.35, 9.63 and 7.60 gP m^-2, respectively. The P. arundinacea population showed the smallest LAI peak(5.4 in early June), and the largest NAR peak (36.9 gDM m^-2wk-1) and RGR peak (0.15g g^-1 wk^-1) among the three species populations. The seasonal change patterns in whole plant EPU of the three species populations showed the bell shape, but the annual EPU values among them were markedly different. It was noticed that the population with the highest RGR showed the highest EPU among the three species populations while the population with the lowest RGR showed the lowest EPU among them.
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