Abstract
Functional specialization of ramets and co-operation between interconnected ramets in heterogeneous environments are studied in this thesis. Since clonal plants can spread horizontally by vegetative growth, a genet has the potential to grow across a heterogeneous environment. Therefore, ramets can functionally specialize in a specific task with different
... read more
forms. In this thesis, I studied the functional specialization of ramets in clonal plant Scirpus olneyi in different communities, seasons, density and environments where resources are inversely distributed.
In Chapter 2 and 3, I studied the clonal architectures of S. olneyi in different communities and seasons. I found that S. olneyi has two types of ramets, Long Rhizome Ramets (LRRs) and Short Rhizome Ramets (SRRs). And in Chapter 3, I found this plant produced a large number of SRRs early in the growing season and subsequently produced LRRs, and plants produce proportionally more SRRs in high quality patches. These results suggested that the task of SRRs was to consolidate occupancy and exploit favorable habitats while the task of LRRs was to explore new and possibly high-quality habitats.
In Chapter 4 and 5, the density effect on the propagation strategy of clonal plants is discussed. In Chapter 4, both garden and field observations showed that S. olneyi produced more seeds and proportionally more SRRs at higher ramet density. This result suggests that as ramet density increases, S. olneyi shifts its propagation strategy from exploration with LRRs to exploitation with SRRs and spreading by seeds. In Chapter 5, a simulation model is developed to evaluate the outcome of competition among clonal plants that have different patterns of reproduction under different densities. The results of simulations showed that producing seeds at higher density is suitable at dense populations. Our garden and model studies suggest, independent of resource availability the production of ramets at lower densities and the production of seeds at higher densities seem to be a proper strategy.
In Chapter 6 and 7, a garden experiment and a mathematical model are conducted to evaluate the degree of specialization of ramets growing in environments where the resource availability is negatively correlated. The experiment showed that ramets of S. olneyi showed the specialization to uptake locally abundant resources, but did not show full specialization. In Chapter 7, a theoretical model is developed to evaluate the degree of specialization in resource capturing under various environmental conditions. The model suggested the importance of the costs of the efficiency of resource capturing. When a plant reaches a larger size, the efficiencies of resource capturing and transport to each organ can decrease possibly because the costs for supports, maintenance and aging increase. Thus, in such a situation, the plant system also allocates biomass to the organ in the poor-quality condition, and this explains why ramets do not show full specialization in resource capturing.
It is likely that functional specialization or ramets is beneficial for clonal plants to explore for resources and exploit favorable patches and enables to dominate in a variety of habitats.
show less
