Study On Population Ecology In A Clonal Plant Of Elymus Excelsus In The Songnen Plains

Elymus excelsus Turcz. is a perennial tuft herbaceous species of Gramineae. Itis better palatability to feed animals, and it is suitable to be cultivated in arid andsemiarid regions, light and intermediate salinization.soil for its better quality. Thisdissertation targeted on natural and experimental Elymus excelsus on the SongnenPlain of China, and population structure, clone structure, growth and production ofclone modules in experimental condition and prolonged reproductive growth ofreproductive tillers in both experimental and natural populations were studied at thelevel of population, clone, and module. Four main conclusions could be obtained fromthe field survey and sample and indoor experiment conducted during two years' periodfrom 2005 to 2006 and they were as follow:At the end of the second growing season, the numbers and biomasses ofvegetative tillers, reproductive tillers and total tillers, and the numbers of winternessseedlings and winterness buds and dormancy modules all had big phenotypicplasticity in different densities of experimental populations established by seedlings.The numbers and biomasses of vegetative tillers, such as reproductive tillersvegetative tillers and the numbers of dormancy modules such as winterness seedlingsand winterness buds all decreased with increasing density. The percentages ofvegetative tillers were all dominant, and the percentages of reproductive tillers wereall smaller. The percentages of winterness seedlings were all dominant. RAâ… , theratio of the biomasses of reproductive tillers to above-ground biomasses, and RAâ…¡,the ratio of the spike biomasses to above-ground biomasses, and RAâ…¢, the ratio ofripe seed biomasses to above-ground biomasses, all decreased with density increasingon the whole. More resources were allocated to reproductive modules, such asreproductive tillers, spikes and ripe seeds in low densities in contrast with highdensities.The E. Excelsus clones were established by two ways: seedlings and youngertillers. After two seasons' growth, the numbers and biomasses of the modules of tillers and the numbers of dormancy modules all had big phenotypic plasticity in differentestablishment ways at the end of the second growing season. The numbers andbiomasses of tillers such as reproductive tillers and vegetative tillers, the numbers ofdormancy modules such as winterness seedlings and winterness buds, the biomassesof winterness seedlings. above-ground biomasses, and RAâ… , the ratio of hiomass ofreproductive tiller to above-ground biomass, and RAâ…¡, the ratio of spike biomass toabove-ground biomass, and RAâ…¢, the ratio of ripe seed biomasses to above-groundbiomasses of clones in different eatablishment ways all decreased with increasingdensity. Some quantity characters of the clones in the same density, which was 45plants/m~2, in the two establishment ways were different. The numbers and biomassesof reproductive tillers, RAâ… , RAâ…¡and RAâ…¢of the clones established by youngertillers were all higher than the ones of clones established by seedlings, and thenumbers and biomasses of vegetative tillers, the numbers of winterness seedlings, andwinterness buds, vegetative tillers, and dormancy modules, and the biomasses of thewinterness seedlings, and reproduction capacity and capacity of vegetativereproduction of single winterness seedling were lower than that of clone establishedby seedlings. There were no differences in the number and the biomass of the totaltillers, and above-ground biomass between the two establishment ways.There was a significant allometric growth correlation between diameter of clusterand number of the tiller of Elymus excelsus experimental clones at ripe stage in eachdensity in two years. The allometric exponents between diameters of clusters and thenumbers of tillers decreased with increasing density, which indicated that the clustersin low densities had enough resources and space to produce more tillers. At the end ofthe second growing season, there was a positive linear correlation between the numberof reproductive tiller and the diameter of cluster, between the number of vegetativetiller and the diameter of cluster, and between the number of tiller and the diameter ofcluster in experimental E. Excelsus clones, respectively. There was a linear positivecorrelation between the biomass of reproductive tiller and the diameter of cluster,between the number of vegetative tiller and the diameter of cluster, and between thenumber of tiller and the diameter of cluster, respectively. There was a positive linear correlation between the number of winterness seedling and the diameter of cluster,between the number of winterness buds and the diameter of cluster, between thenumber of vegetative tillers and the diameter of cluster, and between the number ofdormancy module and the diameter of cluster, respectively.Spike length, tiller height, spike biomass, tiller biomass, reproductive allocationand reproductive growth ratio of the reproductive tillers of natural populations at thesame development stage(early heading stage, heading stage, flowering stage and milkripe stage) sampled every four days, and the reproductive tillers of natural populationswith emergence-ear marked every six days and the reproductive tillers ofexperimental populations with emergence-ear marked every six days all had bigphenotypic plasticity. But they all had the same tendency on the whole that it wasadvantageous to higher growth and more matter reproduction, especially toreproduction allocation with the increasing time of reproductive growth. (2)There wasa significantly positive allometric growth correlation between spike length and tillerheight, tiller biomass and reproductive height, spike biomass and tiller height, spikelength and tiller biomass, spike biomass, spike biomass and reproductive biomass andreproductive growth ratio and spike length. There was significantly negativeallometric growth correlation between reproductive growth ratio and tiller height insome development stages. Allometric relations between spike length and tillerbiomass, and between spike biomass and reproductive biomass, and between tillerheight and tiller biomass were variable. There was no regulation between tiller heightand reproductive allocation, and the values of reproductive allocation fluctuatedaround the mean value.