Population Dynamics And Structure Of Leymus Chinensis And Carex Duriuscula In Restoration Succession Series Of Songnen Degraded Grassland

Leymus chinensis and Carex duriuscula are both rhizome plants. In Songnengrassland, L. chinensis is a dominant species, whereas C. duriuscula is a subdominantspecies. Population dynamics and structures of L. chinensis and C. duriuscula play animportant role in the degradation and restoring succession process. This paper studiedthe mutual dynamics of background plants C. duriuscula and L. chinensis populationswith different initial densities. By observation of the two growing seasons and thesampling measurement at the end of the second growing season, quantitativecharacteristics of mutual dynamics and the age structures of both L. chinensis and C.duriuscula were analyzed, to understand the dynamics of main plants community insimulative degradation and restoration grassland, enrich the restoration successiontheory of plant community and provide theoretical references for the restoration ofdegraded grassland in northeast China. The results showed that:Throughout the second growing season, by the vigorous vegetative propagation, L.chinensis tillers with different initial densities exponentially increased at a0.05or0.01level, but background plants C. duriuscula tillers increasd and then reduced bythe quadratic function. On the whole, the results showed a negative relationship of themutual dynamics between the two populations, with the increase of L. chinensis tillernumber in the1plant/m~2community, C. duriuscula tillers linearly reduced at a0.05level.The growth rate and dynamics of L. chinensis and C. duriuscula populationschanged in initial density communities in two years. Both two populations had a rapidgrowth in June during first year. On the whole, the growth rate of L. chinensispopulations rose up fluctuantly, but the growth rate C.duriuscula populations tendedto decrease; meanwhile, during the growing season of first year. L. chinensispopulations presented a fast growth, and its growth rate was higher than C. duriusculapopulations. In the second year, the actual growth rate of L. chinensis in initial density1plants/m~2and4plants/m~2communities was increasing, but the initial density9plants/m~2showed a trend of decreasing in the process of time. On the whole, theactual growth rate of L. chinensis populations was higher than C. duriuscula. With thetime going, L. chinensis populations increased C. duriuscula was contrary, and ininitial density4plants/m~2and9plants/m~2communities, relationships between twopopulations were significantly linear. The age structure of L. chinensis and C. duriuscula tillers were expanding, L.chinensis populations consisted of two age classes,1a accounted was predominant, anaverage of over92%, C. duriuscula populations did three age classes, but an averageof1a just under80%, Accumulative length and biomass of rhizomes both populationsconsisted of three age classes, which were expanding except for the initial density of1plants/m~2of L. chinensis community, and2a rhizome of C. duriuscula populationswas the most and it was stable.L. chinensis and C. duriuscula include juvenile tillers and buds deriving fromtiller nodes and, respectively. The juvenile tillers deriving from tiller nodes of L.chinensis populations was composed of two age classes and the average proportion of1a is85.8%. Juvenile tillers deriving from tiller nodes of C. duriuscula included threeage classes and the average proportion of1a was64.4%.0age class juvenile tillersderiving from topmost rhizomes of L. chinensis populations accounted for the largest62.5%, except for initial density of1plants/m~2community, but C. duriuscula onlyconsisted of topmost rhizomes.In conclusion, in the community of different initial densities L. chinensis andbackground plant C. duriuscula, whether the increasing trend of L. chinensispopulations tillers, or the mutual dynamics in two years, even age structures oftillers, rhizomes and vegetative propagation potential populations of two populations,L. chinensis populations all showed an obvious advantage. Therefore, with therestoration succession process, L. chinensis was replacing of C. duriuscula as adominant in the community.