Effects Of Environmental Factors On Interspecific And Intraspecific Relationships Of Alternanthera Philoxeroides

Biological invasion is one of the major challenges to the ecological system, in the context of global environmental change, and environmental factors will cause a certain impact on plant invasion. The relationships between different individual plants and the interactions between environmental factors and plants will directly affect the growth, reproduction of individual plants, and even the stability of the communities and the whole ecological systems.Clonal invasive plant Alternanthera philoxeroides is very sensitive to environmental change, due to its clonal traits and morphological plasticity. Because of the way of different species response to the same environmental change is different; the change of environmental factors will inevitably affect intraspecific and interspecific relationship of Alternanthera philoxeroides. At present, the research on the interspecific and intraspecific relationships of Alternanthera philoxeroidesis still not enough, this study set up four greenhouse experiments, gradually explored the effects of environmental factors on interspecific and intraspecific relationship of Alternanthera philoxeroides, which will provide the corresponding data and theoretical basis for biological invasion prevention and control. The main contents and results were as follows:(1)Plants grew more in the heterogeneous than in the homogeneous treatment, showing that heterogeneity promoted performance; they grew less in the high- than in the low-density treatment, showing that plants competed. There was no interactive effect of nutrient heterogeneity and plant density, supporting the hypothesis that heterogeneity does not affect intraspecific competition in the absence of genotypic differences in plasticity. Treatments did not affect morphological characteristics such as specific leaf area or root/shoot ratio.(2) N addition significantly increased growth of both A. philoxeroides and A. sessilis., and N pulse significantly modified neither growth nor interspecific competition of both species. In this study, the sufficient soil water content and nutrients other than N provided may be a reason for no effects of N pulse on competition of the two species. Alternatively, high tolerance of both species to low soil nutrients and water content may lead to less strong responsiveness to N pulse. The results indicate that increasing atmospheric N deposition in the context of climate change may change population structure and dynamics of both species, but may not affect interspecific competition of these plants.(3) Presence of A. philoxeroides decreased the growth of the other four species, and competitive effect was greater when plants were not flooded than when they were. Fragmentation of A. philoxeroides did not reduce its competitive effect or production of new ramets or stems, though it did reduce its total accumulation of mass. Results suggest that clonal plants may mitigate trade-offs between the potential ecological advantages of integration and fragmentation by maintaining vegetative reproduction even when total growth is reduced.(4) The invasion ability of Alternanthera philoxeroides is weakened by the increase of biodiversity and the existence of a dominant species of local communities. These results indicated that maintaining plant community biodiversity and protecting the local dominant species are two effective measures to decrease the invasion of exotic plant.