Research Of Floating Bed Plants Ecological Features And Its Effects On Phytoplankton Community

In order to research the ecological features of floating bed plants building on a natural water area, supporting by the ecological floating bed project in Dianshan lake, we chose Canna indica(M), Iris pseudacorus(H), Thalia dealbata(Z), lythrum salicaria(Q) as tested plants. To study the growth situations of the test plants, we analyzed plant height, leaf number, tillering number, biomass and surviving ratio of floating bed plants. To learn the biomass allocation pattern of tested plants, we made comparison of the above-water proportions and below-water proportions of each kind of plants, the root number and length of the 4 kinds of plant. To fully understand the allocation pattern of tested plants, we matched root number, total root length and tillering number with biomass of below water proportion to get the allometric growth parameters. To answer the questions that how about the absorbing capacity of floating bed plants we chosen, which plant performed the highest C,N,P content, what the limiting elements during the plant growing was, we studied the ecological stoichiometry of the floating bed plants. Ecological floating bed technology was for the water eco-system restoring. Thus, people wanted to know the effects of ecological floating bed affecting the phytoplankton community during a year. So we comparing the phytoplankton density, species composition, index of biological diversity to get know the effects. The main results of this research work are as follows:(1) After 2 months growing, M and Z made the highest survival ratio among the 4 kinds of plants, which were 83.33%. The survival ratio of Q was lower the M and Z, which was 76.67%.H performed the lowest survival ratio among the tested plants, which was 48.15%. The survival rate of tested plants shows that all 4 kinds of plant can adapt to the research environment, the survival rate of H was relatively lower than the other 3 kinds of plant. At the end of growth season, the average plant height of Z was significantly higher than the other tested plants, which was 241.26 cm. The average height of M was significantly higher than both Q and H, which was 169.34 cm. The average plant height difference of Q and H was not significant, which were 147.60 cm and 138.33 cm respectively. Average tillering numbers of M and Z were significantly higher than the other two kinds of plants, which were 64.3 and 77.3 tillering/cluster. Average tillering numbers of Q and Z were 42.3 and 54.3 tillering/cluster. At the end of growth season, the average biomass of Z was 3651.67 g, which was 373.06 times of the biomass at the beginning growth season; The average biomass of M was 2402.53 g, which was 373.06 times of the biomass of M at the beginning of the growth season; The average biomass of Q and H were 997.40 g and 857 g, respectively; The result of ANOVA showed that the average biomass of M and Z were significantly higher than the average biomass of Q and H. The seasonal average respective growth rate were as follows from the highest to the lowest:Z(16.38 g/(d-plant))>M(10.60 g/(d-plant))>Q(4.34 g/(d-plant))>H(3.65 g/(d-plant)). The highest respective growth rate of M were 29.14 g/(d-plant), appearing during August and October. The highest respective growth rates of Z and H appeared during October to November, which were 66.28 g/(d-plant) and 15.96 g/(d-plant) respectively. The growth rate of Q presented a bimodal type, appearing during April to August and October to November, which were 6.68 g/(d-plant) and 5.72 g/(d-plant), respectively. In conclusion, the trends of all kinds of physiological parameters of M and Z presented steady increase during the experiment time, the biomass of M and Z were significantly higher than H and Q. These phenomenon deduced that the growth statuses of M and Z were quite well, so these two kinds of plants can be generalized as the ecological plants in condition of the climate of the research area.(2) At the end of the growing season, the average root number of M, H, Z and Q were 733.80,1183.33,2871.50 and 12660.33 per plant, respectively. The average lengths of floating bed plants were as follows from longest to shortest:H (57.57 cm)>Q (50.33 cm)>M (47.76 cm)>Z (32.45 cm). The root lengths of M and Z developed rapidly to the highest level after the first two months, did not grow significantly longer. M and Z developed more root number during the rest growth season to absorb enough nutrients and water. The root development strategies of Q and H were increasing root length and numbers at the same time. The above-below water biomass allometric growth parameters of M, H, Z and Q were 1.07,0.94,1.09 and 1.03, respectively. The confidence interval was 95%, so there were no significantly different between 1.00 and the above-below water biomass allometric growth parameters of M, Z and Q. The above-below water biomass allometric growth parameters of H showed that the above-water proportion biomass of H was grown slower than the below-water proportion biomass. Except total root length of Q was growing faster than below-water proportion biomass, the other plants performed the contrast. All of the 4 kinds floating bed plants showed that the root number and tillering number grown slower than below-water proportion biomass. The ratio of root to crown of floating bed plants, related to the resources allocation during the plant growth season, presented trend that first decreased then rise. The linear relationships between above-water proportion biomass and below-water proportion biomass of tested plants were significantly positive. Based on the linear fitting formula, the biomass of the below-water proportion can be predicted by the biomass of above-water proportion without pulling out the plants or damaging the floating bed.(3) The range of average TOC (total organic carbon) contents of the above-water proportion and below-water proportion of floating bed plants were 354.35 to 409.81 g/kg and 272.34 to 343.41 g/kg, respectively. The range of average TN (total nitrogen) contents of the above-water proportion and below-water proportion of floating bed plants were 24.49 to 26.75 g/kg and 14.31 to 28.48 g/kg, respectively. The range of average TP (total phosphorus) contents of the above-water proportion and the below-proportion of floating bed plants were 1.05 to 2.15 g/kg and 0.79～2.01 g/kg, respectively. The C, N and P absorbing amounts of M and Z were significantly more than H and Q (p< 0.05). Time variations of C:N ratios of tested plants were not absolutely conformities. C:N ratios of M and H were decreased along with the time. The C:N ratios of M and H were 10.61 to 18.04 and 11.77 to 19.90. The C:N ratios of Z and Q were 14.55 to 22.27 and 11.78 to 19.71.The C:N ratios of tested plants were closed to the C:N ratio of the grassland in China. This phenomenon proved that the C:N ratio was quite stable among the species of herbaceous plants. The general trends of C:P ratio of tested plants were decreased along with time. The trends of C:P ratio can predict the fast growing of tested plants in some level, but the value of C:P ratio was not conformities with the relative growing rate. The seasonal average of N; P ratios of Z and H were 26.69 and 24.83, respectively, which indicated that the growth situation of these two plants were P limited. The seasonal average of N:P ratios of M and Q were 14.87 and 19.27, which indicated that the growth sitaation of these two plants were N limited. At the beginning of the growing season, the N:P ratio of Q was 26.69, which was higher than 23.00, this phenomenon indicated that the growth situation was P limited.The N:P ratios of the other three plants at the beginning of the growting season were all lower than 21.00, which indicated that these 3 kinds of plant were N limited. In April, the N:P ratios of tested plants were all higher than 23.00, the limiting element of the floating bed plants was P. When in October, the N:P ratios of tested plants were all lower than 21.00 again, the limiting element was N.(4) A total of 8 phylum,108 genera,327 species of phytoplankton were identified (with varietas and metatype). The phytoplankton community was mainly composing by Chlorophyta, Cryptophyta, Bacillariophyta, Cyanophyta and Euglenophyta. These five phylum contributed over 90% of the total phytoplankton individuals. The comparison of the spring and summer phytoplankton densities of floating bed area and the control area showed that phytoplankton densities in spring and summer decreased about 21.29% and 17.23%, respectively. In May and July, Oscillatoria tenuis, Chroococcus minor, Chamydomonas globosa and Ulothrix flaccidum were bloomed= When the algal bloomed in May, the Chl-a concentration of the control area was 122.18 μg/L while the Chl-a concentration of floating bed area was just 63.43μg/L which was about 51.84% to the Chl-a concentration of the control area. In July, the Chl-a concentration of the control area was 69.04 μg/L while the Chl-a concentration of floating bed area was 37.50 μg/L which was about 54.32% to the Chl-a concentration of the control area. The Shannon-weaver indexes and Pielou indexes of floating bed area were higher than those indexes of the control area. Except in spring, the Marglef indexes of floating bed area were all higher than those of the control area. This phenomena deduced that the ecological floating bed can improve the complexity of the phytoplankton community and had positive effect to improving the stabilization of the phytoplankton community. Correlation analyze of the main phylum densities of phytoplankton and the physical and chemical parameters of water in research area showed that Bacillariophyta were not sensitive to the physical and chemical parameters; Euglenophyta showed significantly negative to the TN concentration; Chlorophyta and Cryptophyta showed significantly positive to the DO concentration. Cyanophyta of the floating bed area were significantly negative to the TN:TP ratio, and was not sensitive to TN:TP ratio of the control area.