Search

Abstract: Raised field agriculture is a typical human-modified landscape of most shallow lakes and coastal saline-alkali areas in north China. Local farmers have constructed more than 9400ha of raised fields for agricultural production in Baiyangdian Lake, the largest lake in the North China Plain. Most of the raised areas are 2- 4 m higher than the water level and 30-50 m wide. The canals surrounding these platforms are 2-10 m wide. The objective of this research was to obtain experimental information on a number of processes that affect the agricultural production of the raised fields system, such as the cultivation of Phragmites australis. Since aquatic plants mature in spring and summer, the field experiments were conducted in May, 2011. The ecological environment and economic benefits were analysed and it was concluded that raised fields have a positive impact on the control of water quality. [Copyright &y& Elsevier]

Macrophyte decomposition can significantly influence aquatic carbon and nutrient cycling, especially in eutrophic shallow lakes, in which incomplete decomposition of detritus may lead to sediment accumulation and accelerate lake aging. In order to explore the role of macrophyte decomposition in lake terrestrialization, six major aquatic plants (two submerged, two floating, and two emergent species) in Lake Baiyangdian were investigated in this study. Detritus of these species were placed at three sites with different pollution intensities to investigate the contributions of plant species, site nutrient condition, and their interactions on detritus decomposition. Detritus decomposition was represented by detritus mass remaining at each sampling time. Results of this study suggest that although decomposition processes are species and site specific, and the effects of species are stronger than site conditions. Initial detritus phosphorus (P)-related indicators were proved to be effective controllers for detritus decay at the later stage of the experiment. Significant interactions between site and species indicate that plant species also influenced site controls on detritus mass loss. Site effects on decomposition were significant for submerged and floating species (P <0.01), and slightly significant for emergent species (P <0.05). A mathematic two-stage decomposition model was developed based on the experimental results using stepwise analysis to analyze effects of detritus quality and site conditions on decomposition. The detritus quality indicators were the main contributors for both early and later stages of detritus decomposition, while the site nutrients only affected decomposition at the later stage. [Copyright &y& Elsevier]