Bacterioplankton play key roles in the biogeochemical cycle and in organic contaminant degradation. The species richness and abundance of bacterial subgroups are generally distinct from each other, and this is attribu...Bacterioplankton play key roles in the biogeochemical cycle and in organic contaminant degradation. The species richness and abundance of bacterial subgroups are generally distinct from each other, and this is attributed to their different functions in aquatic ecosystems. The spatiotemporal variations of eight phylogenetic subgroups （Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Planctomycetes, alpha-, beta-, and gamma-Proteobacteria） derived from Donghu Lake were investigated using PCR-DGGE fingerprinting, to explore their responses to environmental factors. Results indicate that Actinobacteria and beta-Proteobacteria were the two largest bacterial subgroups detected. These two groups and Bacteroidetes showed clear seasonal patterns in composition of the operational taxonomic unit. Results also suggest that the bacterioplankton subgroups in Donghu Lake were significantly correlated with different environmental factors. In brief, the total nitrogen was one of the major factors regulating all the bacterioplankton except for Actinobacteria. However, total phosphorus, another important eutrophication factor, contributed to the two largest bacterial groups （Actinobacteria and beta-Proteobacteria）, as well as to the Cyanobacteria and Firmicutes. Therefore, the responses of bacterioplankton subgroups to environmental factors were different, and this should be attributed to the differences in the fimctions of different groups.展开更多
Through the long-term plot study on the litter and its decomposition in the evergreen broad-leaved forest ecosystem in Hangzhou for more than two years,it was resulted that the annual litter production was 5.85 t ha^-...Through the long-term plot study on the litter and its decomposition in the evergreen broad-leaved forest ecosystem in Hangzhou for more than two years,it was resulted that the annual litter production was 5.85 t ha^-1,most of which was the fallen leave (79.5 percent) and the withered branches and fruits were far less (7.1 and 13.4 percents respectively).The dynamics of the fallen litter was shown as a curve of two-peak pattern which appeared in April and September each year.The half-life of the litter was 1.59 years.The decay rate of the litter attenuted as an exponential function.The annual amount of the nutrient returned to the ground through the litter was as large as 223.69kg ha^-1.The total current amount of the litter on the ground was 7.47t ha^-1.The decay rate in the first half of a year was 45.18 percent.This ecosystem remained in the stage of litter increasing with time.展开更多
Disease in ecological systems plays an important role. In the present investigation we propose and analyze a predator-prey mathematical model in which both species are affected by infectious disease. The parasite is t...Disease in ecological systems plays an important role. In the present investigation we propose and analyze a predator-prey mathematical model in which both species are affected by infectious disease. The parasite is transmitted directly （by contact） within the prey population and indirectly （by consumption of infected prey） within the predator population. We derive biologically feasible and insightful quantities in terms of ecological as well as epidemiological reproduction numbers that allow us to describe the dynamics of the proposed system. Our observations indicate that predator-prey system is stable without disease but high infection rate drive the predator population toward extinction. We also observe that predation of vulnerable infected prey makes the disease to eradicate into the community composition of the model system. Local stability analysis of the interior equilibrium point near the disease-free equilibrium point is worked out. To study the global dynamics of the system, numerical simulations are performed. Our simulation results show that for higher values of the force of infection in the prey population the predator population goes to extinction. Our numerical analysis reveals that predation rates specially on susceptible prey population and recovery of infective predator play crucial role for preventing the extinction of the susceptible predator and disease propagation.展开更多
基金Supported by the National Natural Science Foundation of China(No.31071896)the National Basic Research Program of China(973 Program)(No.2008CB418105)+2 种基金the Knowledge Innovation Program of Chinese Academy of Sciences(No.Y15E04)the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.Y22Z07)the Key Laboratory of Marine and Estuarine Fisheries Resources and Ecology,Ministry of Agriculture(No.201007)
文摘Bacterioplankton play key roles in the biogeochemical cycle and in organic contaminant degradation. The species richness and abundance of bacterial subgroups are generally distinct from each other, and this is attributed to their different functions in aquatic ecosystems. The spatiotemporal variations of eight phylogenetic subgroups （Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Planctomycetes, alpha-, beta-, and gamma-Proteobacteria） derived from Donghu Lake were investigated using PCR-DGGE fingerprinting, to explore their responses to environmental factors. Results indicate that Actinobacteria and beta-Proteobacteria were the two largest bacterial subgroups detected. These two groups and Bacteroidetes showed clear seasonal patterns in composition of the operational taxonomic unit. Results also suggest that the bacterioplankton subgroups in Donghu Lake were significantly correlated with different environmental factors. In brief, the total nitrogen was one of the major factors regulating all the bacterioplankton except for Actinobacteria. However, total phosphorus, another important eutrophication factor, contributed to the two largest bacterial groups （Actinobacteria and beta-Proteobacteria）, as well as to the Cyanobacteria and Firmicutes. Therefore, the responses of bacterioplankton subgroups to environmental factors were different, and this should be attributed to the differences in the fimctions of different groups.
基金Project supported by the Laboratory of Material Cycling in Pedosphere, Insitute of Soil Science, Chinese Academy of Sciences.
文摘Through the long-term plot study on the litter and its decomposition in the evergreen broad-leaved forest ecosystem in Hangzhou for more than two years,it was resulted that the annual litter production was 5.85 t ha^-1,most of which was the fallen leave (79.5 percent) and the withered branches and fruits were far less (7.1 and 13.4 percents respectively).The dynamics of the fallen litter was shown as a curve of two-peak pattern which appeared in April and September each year.The half-life of the litter was 1.59 years.The decay rate of the litter attenuted as an exponential function.The annual amount of the nutrient returned to the ground through the litter was as large as 223.69kg ha^-1.The total current amount of the litter on the ground was 7.47t ha^-1.The decay rate in the first half of a year was 45.18 percent.This ecosystem remained in the stage of litter increasing with time.
文摘Disease in ecological systems plays an important role. In the present investigation we propose and analyze a predator-prey mathematical model in which both species are affected by infectious disease. The parasite is transmitted directly （by contact） within the prey population and indirectly （by consumption of infected prey） within the predator population. We derive biologically feasible and insightful quantities in terms of ecological as well as epidemiological reproduction numbers that allow us to describe the dynamics of the proposed system. Our observations indicate that predator-prey system is stable without disease but high infection rate drive the predator population toward extinction. We also observe that predation of vulnerable infected prey makes the disease to eradicate into the community composition of the model system. Local stability analysis of the interior equilibrium point near the disease-free equilibrium point is worked out. To study the global dynamics of the system, numerical simulations are performed. Our simulation results show that for higher values of the force of infection in the prey population the predator population goes to extinction. Our numerical analysis reveals that predation rates specially on susceptible prey population and recovery of infective predator play crucial role for preventing the extinction of the susceptible predator and disease propagation.
