Impacts Of Urbanization On Plant Diversity: Methods, Patterns And Mechanisms

Impacts of urbanization on plant biodiversity is one of the hotspots in current biodiversity research. However, there are no unanimou sampling method suitable to urban plant diversity investigation. The spatial distribution patterns of plant diversity along urban-rural gradient and the underlying maintenance mechanisms are still not clear. This thesis aims to development a sampling method appropriate to investigate plant species richness in urban habitats, to identify the spatial distribution pattern of plant diversity along urban-rural gradient, to explore the how land use and land cover type and landscape pattern influnce the spatial pattern of plant biodiversity, and finally to relate urbanization intensity to plant species richness using two 9km-width transects across urban center to rural areas in Shanghai. My findings are as following:1. The innovated modified Whittaker (MW) plot sample method which we called Split Modified Whittaker(SMW) sampling plot has. higher sampling efficiency and accuracy than MW and 900m2 (30×30m) sampling plots which demonstrated that SMW sampling plot is a suitable method for plant diversity investigation in heterogeneous urban habitats.2. The cumulative plant species and perennial herbeceous species peaked at the interfaces where moderate urbanization degree exsits, but were lowest in rural areas along the two urban-rural transects, while woody plant species richness decreased with urbanization degree. The annual herbaceous speccies richness exhibited a sparial pattern of lowest value in urban center.3. Urban land use affects plant species richness. The percentage of residential land, public facilities and road exhibited significant positive correlation with cumulative species, woody species and perennial herbaceous species richness, but negative correlation with annual herbaceous species richness. However, the percentage of farmland presented significant negative correlation with cumulative species, woody species and perennial herbaceous species richness, and a significant positive correlation with annual herbaceous species richness.4. Urbanization degree influnces plant species richness. There were quadratic polynomial relationship between urbanization degree and cumulative plant species, annual and perennial herbaceous species richness. However, linear relationship existed between woody species richiness and urbanization degree.5. Urban landscape patterns influence plant species richness, higher richness of cumulative species, woody and perennial herbaceous species occurred in urban habitats with larger area, simpler shape and better connectivity, while annual herbaceous species existed in urban habitats with higher shape complexity and lower connectivity.The results mentioned above are helpful to enhance our understanding the impacts of urbanization on plant species diversity in urban environment.