关键词: 稻茬麦根系, 根构型, 周向分布, 投影面分形分析

Abstract: Lake Fuxian is a typical deep oligotrophic lake located in YunnanGuizhou Plateau. In order to explore the spatial distribution characteristics of the phytoplankton community and its influencing factors, stratified sampling, including three sites, was conducted in July 2014. A total of 37 species, belonging to 27 genera, 18 families and 6 phyla, were identified in our survey. The average biomass of phytoplankton across the whole lake was 0.41 mg·L^-1, of which Chlorophyta exceeded 70%. Mougeotia sp., which belongs to Chlorophyta, was the absolutely dominant species with a biomass of 0.18 mg·L^-1. In horizontal distribution, biomass of phytoplankton was higher in the north than those in the middle and south. In water column, phytoplankton was mainly distributed in epilimnion and thermocline layers with a maximum occurring at a depth of 10 m, and the biomass decreased remarkably in hypolimnion layer. Correlation analysis suggested that biomass of phytoplankton in epilimnion and thermocline layers was mainly influenced by water depth (accompanied with water temperature and light), while in hypolimnion layer the key affecting factors were DO and pH. Redundancy analysis demonstrated that environmental variables well explained the variations in phytoplankton communities. Water temperature, electric conductivity and pH played key roles in structuring phytoplankton communities, while the role of N and P nutrients was not significant.

Key words: post-paddy wheat root, root architecture, circumferential distribution, projection surface fractal analysis.