Dynamics And Life History Patterns Of Zoysia Japonica Populations In Liaodong Peninsula Of China

Zoysia japonica Steud. is a typical clonal grass plant with underground rhizomesand aboveground stolons, which is mainly distributed in the Liaodong and JiaozhouPeninsulas in China. By establishing the experimental Z. japonica clone and samplingthe natural Z. japonica populations, this paper analysed the dynamics of Z. japonicaclone and populations, and studied the life history patterns of Z. japonica populations.The results indicated that:1. The ramets of Z. japonica clones increased with time by exponent function,the main stolon elongated with time by linear function, and the number of spacers onthe main stolon increased with time by logarithm function. The radius and area ofclones expanded with time by linear and exponent function, respectively.2. The number of Z. japonica ramets changed little in un-burned site andunder-forest site in2006, and large in burned site and in under-forest site in2005. Thechanging trends of bud numbers were similar in three sites. The length of rhizomeswas longer at the beginning and end of the growth season than in the middle of thegrowth season in these three sites.3. The mass of litter decreased in un-burned site and almost did not change inburned site with time. The number and biomass of other species were both lower inburned site than un-burned site. The burning improved the ecological condition andcould lead other species and their seeds to die. Thus, the numbers of all Z. japonicamodules were higher in burned site than un-burned site. The modular numbers werelower in under-forest site than un-burned site due to the limitation of light and soil.4. In the structure of stage classes, the percentage of vegetative adult ramets waslargest (more than64.5%), and the those of buds and juvenile ramets were18.5%and14.2%, respectively. In the structure of biomass, the percentage of rhizome mass waslargest (51.7%), and the those of buds and foliage mass were24.9%and23.3%,respectively.5. The population growth rate (λ) of Z. japonica in burned site was highest（λ=1.1247） between May and June, and less than one （λ=0.557）betweenSeptember and October. The population growth rate in un-burned site was highest（λ=1.1374）betweenAugust and September, and less than one （λ=0.674）betweenSeptember and October. The population growth rate in under-forest site was highest（λ=1.1904） between September and October, and more than one in all growthseason. The main life history pathway was adult ramet pathway‘in three sites, whichmeant that the stasis of adult ramets made the biggest contribution to λ to keep thepopulation relatively steady. The increased λ resulted from the contributions ofvegetative propagation and growth of transition classes.6. The propagules were composed of the rhizomes, stolons and ramets. Thecontribution rates of rhizome to buds and juvenie ramets were more than95%and90%in the natural Z. japonica populations, respectively. However, in experimental Z. japonica clones, the propagules were only composed of the stolons and ramets whichplayed the same important roles. The vegetative fertility of experimental Z. japonicaclone was increased with time by exponent function. The fertility of the natural Z.japonica populations varied between different periods and its time patterns weredifferent among sites.7. Burning extremely significantly decreased the number of seed per spike, andinsignificantly affected the weight of1000seeds, but extremely significantlyincreased the density of reproductive ramets. Thus, the seed yield in burned site was1.85times as high as in non-burning site. The quantitative relationships of thosequantitative characters to the height of reproductive ramets were same in burned andun-burned sites, respectively.8. The number of Z. japonica seeds in droppings of cattle and sheep per gramwas101.7and6.88, respectively. The ingestions of cattle and sheep increased thegermination percentage, germination energy, and vigor index of Z. japonica seeds,and shortened their germination time, but did not affect the viability; A number ofseedlings (134.40seedlings/pat) were established from cattle dung pat. A fewseedlings (0.17seedlings/pellet) were established from sheep pellets. These resultssuggest that cattle and sheep have the relevant potential of endozoochory as Z.japonica seed dispersers.9. The total biomass and the biomass of modules all increased with thepopulation size(population density), the biomasses of modules also increased withtotal biomass, and the biomasses of leaf, leaf sheath modules also increased with thebiomass of ramets all by the linear equation. The56.43％and43.57％of theincreased total biomass was allocated to ramets and rhizoms, and the50.23％and49.77％of the increased biomass of ramet was allocated to leaf sheath and leaf,respectively.