Effects of soil fertility on early development of wetland vegetation from soil seed bank: Focusing on biomass production and plant species diversity

To examine the effects of soil fertility on biomass production, plant species diversity, and early vegetation development, we performed a mesocosm experiment using soil seed bank under three soil fertility levels (ombrotrophic, mesotrophic, and eutrophic). Biomass production linearly increased ( P < 0.01), whereas plant species diversity significantly decreased ( P < 0.001) as soil fertility increased. Soil fertility seemed to play a role as an environmental sieve in early vegetation development, in turn, lead the patterns of biomass production and plant species diversity. Several Poaceae species which are forming tall and dense canopy, such as Phalaris arundinacea , Miscanthus sacchariflorus , and Zizania latifolia , showed higher importance values under fertilized condition, whereas relatively small macrophytes of Eleocharis acicularis , Carex dickinsii , and Isachne globosa mainly survived under ombrotrophic condition. Although plant species richness decreased as soil fertility increased, the percentages of perennials and exotics increased rather than annuals and natives. Predominance of perennials and exotics under eutrophic condition in early vegetation development seemed to lead a continuous decrease in plant species diversity as a result of competitive effect. A significant negative relationship between plant species diversity and biomass production ( P < 0.0001) was obtained when all experimental plots are included in correlation analysis.