Population Ecological Study On Three Stoloniferous Clonal Plants In Tropic Region Of China

Carpetgrass (Axonpus compressus (Sw.) Beauv.), Aciculate Chrysopogon {Chrysopogon aciculatus (Retz.) Trin. ) and Bermuda Grass (Cynodon dactylon (L.) Pers.) are three perennial stoloniferous geasses widely distributed in the Hainan Island of tropical regions of China. They are typical clonal plants for exploiting germplasm of lawn and also are the main occupied population of tropical secondary vegetation. Researches on the population dynamic, population growth and the reproductive strategy of the three stoloniferous grasses from tropical regions was important and useful for revealing the mechanism of bioecological adaptation as well as that in enriching the ecological theory and application. The growth rules, dynamics of temporal and special were performed based on the research of three planted clones. Furthermore, the reproductive characteristics of natural population were also tested in the same or different habitats. Results showed that:1 Three species of clone taken on the similar type of extending. The main stolon elongated as long as possible to occupied the ecological niche. The expending size of the main stolon was Carpetgrass> Bermuda Grass> Aciculate Chrysopogon, and its increasing rate reduced vary with time. The positive correlation between the number of ramets and the length of main stolon as well as the dynamic change of spacer were all showed that the spacial structure of clone was gathered around genet and the extending of clone was due to the contribution of genets and the senior ramets.2 Aciculate Chrysopogon and Carpetgrass clone always keep the growth pattern of matrix and not limitless in enough space. The number and biomass allocation of two grasses show that there are matter and energy trade-off between the growth and the extending and it is the convergentadaptation of stoloniferous grasses that own the same life form.3 The leaf population of the three grasses owns the same growth and development rule. Number of leaves and its increasing rate implied that the change of the matter production and invested target. The changes of total leaves from main stolon and the elongating of main stolon indicated the harmonized development rules.4 The rule of biomass allocations of Axonpus compressus(Sw.) Beauv. and Chrysopogon aciculatus (Retz.) Trin. ) populations disclosed that the capacity of expanding vegetation occupying the space were limited. This concordance embodied their convergency adapting to the environment. While the variational difference of two species showed the difference of ecological niches between species.5 There were significant relationship between the number of nodes of the main stems and the length of the nodes, and the modules of the numbers and the length of the nodes varying with the time disclosed the same changing rule of vegetative propagation capacity of stoloniferous gramineae herbages.6 As for reproductive branch of the natural populations, the orders of the reproductive ratios and reproductive allocation of the three gramineae herbages were Axonpus compressusiSw.) Beauv.> Chrysopogon aciculatus (Retz.) Trin.> Cynodon dactylon (L.) Pers..There were significant and very significant relationships between the reproductive ratios and reproductive allocation of the three gramineae herbages and other amphigenetic quantitative characteristics,such as the length of the spike, the weight of the spike, the height of the ramets, the weight of the ramets, et al.,which showed that amphigenetic process of stoloniferous clonal species populations were controlled by growth rhythms of the species themselves, and the growth time and biotemperature were vital ecological effect to the reproductive strategies.7 Reproductive characteristics of Cynodon dactylon (L.) Pers. populations in different environments represented heredity and plasticity of the species.