| Leymus chinensis is a dominant species, and Carex duriuscula and Hierochloe glabra are two important companion species on the Songnen meadows in China. Population dynamics between L. chinensis and C. duriuscula as well as H. glabra were the key point during restoration succession. In this work we studied the quantitative characters and population dynamics of L. chinensis and C. duriuscula grown in each transplanted spot (Transplanted proportion of L. chinensis and C. duriuscula were 1:0, 1:1, 1:2, 1:3, 1:4, 1:5 and 1:6, respectively) and grown on the natural grasslands during restoration after flood, and we analyzed the same as above of L. chinensis and H. glabra grown in each spot (Transplanted proportion of L. chinensis and H. glabra as has been said before) and grown on the natural grasslands during restoration after returning plough to sowing grassland. In six growing seasons, based on the age structures of plant populations, we quantified the mutual dynamics between plant populations, and evaluated the contribution of potential population to population dynamics, and we tended to forecast exactly population dynamics. They are important to restoration succession theory and restoration practice of meadow ecosystem.1. Researches on quantitative characters and population dynamics of L. chinensis and C. duriuscula in each transplanted proportion approved that:(1) Age structures of L. chinensis tillers, C. duriuscula tillers and L. chinensis rhizome composed of 2-4 age classes, and those of C. duriuscula rhizome did 2-5 age classes. They indicated the expansive or stable structures in each plot from 2003 to 2007. Compositions of age gradually increased with time. The tillers in all spots and rhizomes in the great mass of spots had tended to level off in 2006 and 2007. The spatial number of modules of L. chinensis and C. duriuscula didn't stabilize until 2007.(2) Power, exponential or linear equations best explained the seasonal dynamics between L. chinensis tillers and C. duriuscula tillers at significant or extremely significant level from 2002 to 2004. Power equations best explained the yearly dynamics between L. chinensis tillers and C. duriuscula tillers at extremely significant level from 2002 to 2007.(3) L. chinensis population was much higher than C. duriuscula's in the productivity of tiller nodes and rhizome, and storage of potential population from 2002 to 2007.2. Researches on quantitative characters and population dynamics of L. chinensis and H. glabra in each transplanted proportion approved that:(1) Age structures of L. chinensis tillers and rhizome composed of 2-4 age classes and showed the trend from expansive to stable. Age structures of H. glabra tillers did 1-2 and their rhizome did 1-3 age classes. These indicated the expansive or stable structures in each plot from 2003 to 2007. Compositions of age gradually increased with time on the whole. Tillers, rhizomes and potential populations suddenly decreased since 2004. The tillers and rhizomes in the great mass of spots had tended to level off in 2006 and 2007. The spatial number of modules of L. chinensis and H. glabra wasn't steady until 2007.(2) Power or linear equations best explained the seasonal dynamics between L. chinensis tillers and H. glabra tillers at extremely significant level except for 1:4 spot from 2002 to 2004. Quadric equation best explained the yearly dynamics of single dominant H. glabra tillers, and rhizomes decreased exponentially from 2002 to 2007. Only in 1:1 and 1:6 spots, the yearly dynamics between L. chinensis and H. glabra tillers were significant, and rhizome dynamics between two populations were negatively correlative from 2002 to 2007.(3) L. chinensis population was much higher than H. glabra's in the productivity of tiller nodes and rhizome, and storage of potential population from 2002 to 2007. The storage capacity of L. chinensis was 1.65-5.66 times that of H. glabra. In same spot, mean productivity of L. chinensis was 1.91-3.35 times that of H. glabra.3. Researches on quantitative characters and population dynamics of L. chinensis and C. duriuscula during restoration succession after flood approved that:(1) The tillers consisted of four age classes in the center of every patch and did three age classes at the edge in L. chinensis population. Age structures of the tillers were stable in the center of every patch and would be expansive with the growth of patches. The rhizomes consisted of two to four age classes in the center of every patch and in the middle, while one to two age classes at the edge. The rhizome length of L. chinensis population was expansive age structure in every circle. Potential population including juvenile tillers and buds of tiller nodes, consisted of four age classes in every circle. The potential populations were expansive age structures in every circle, and presented expansive tendency from the centers to the edges of different radius patches, respectively. The young tillers and rhizomes had vigorous matter productivity and storage capacity on the whole. From the center to the edge of every patch the matter production and storage were consistent with the trend of patch expansion.(2) During restoration succession after flood in the meadow on the Songnen Plains of China, the number of and the biomass of the tillers of L. chinensis population decreased with the circles, those of C. duriuscula population increased with the circles from the center to the edge of five clonal patches with different radius. The productivity of per tiller of L. chinensis weakened and that of C. duriuscula intensified gradually at the same time. The number of the tillers of L. chinensis increased and C. duriuscula decreased gradually from the center of 0.5 m to 5 m patches. At the center and neighbouring area of 10 m patch, L. chinensis tillers tended to stable.(3) The mean productivity of L. chinensis tiller nodes was 3.34 times and 1.18 times that of C. duriuscula. The mean productivity of L. chinensis rhizomes was 1.42 times and 2.15 times that of C. duriuscula in 2003 and 2004. The storage of potential population and contribution to population dynamics of L. chinensis were much higher than C. duriuscula in two years.4.Researches on quantitative characters and population dynamics of L. chinensis and H. glabra during restoration after returning plough to sowing grassland approved that:(1) Age structure of L. chinensis tillers composed of 3 age classes,and H. glabra tillers did 2-3 age classes,and showed expansive classes structure. Age structure of L. chinensis rhizome did 4 and H. glabra rhizome did 2-3 age classes, and these indicated expansive or stable class structures in each plot from 2003 to 2007. The potential of vegetative reproduction of L. chinensis tiller nodes and rhizomes were higher than H. glabra's.(2) The dynamics between L. chinensis and H. glabra tillers were significant or extremely significant negatively correlative in 2003 and 2004. Most correlations between two population rhizomes were significant. H. glabra tillers and rhizomes decreased with the increase of L. chinensis tillers and rhizomes in both years.(3) The mean productivity of tiller nodes and rhizomes was lower than that of H. glabra's, and total potential population was higher than H. glabra in 2003. The productivity of L. chinensis tiller nodes, rhizomes and total storage capacity were higher than H. glabra's.During restoration of experimental and natural communities, L. chinensis would become the dominant plant and C. duriuscula did companion species in the L. chinensis + C. duriuscula communities again. L. chinensis would become the single dominant plant and H. glabra would disappear in the L. chinensis + H. glabra communities.
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