In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies....In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorurn, but no significant effect is found in this study.展开更多
The effect of three organic materials (rice straw, Chinese milk vetch and pig manure) on the fractionationof cadmium added into two soils (a red soil and a fiuvo-aquic soil) was studied using submerged incubationexper...The effect of three organic materials (rice straw, Chinese milk vetch and pig manure) on the fractionationof cadmium added into two soils (a red soil and a fiuvo-aquic soil) was studied using submerged incubationexperiment. The organic materials increased soil solid organic carbon (SOC), pH value, the concentration ofactive Si in all the treatments and active Fe and Mn in some treatments. Accumulated SOC caused directlythe increase of Cd bound to solid organic matter and consequently the decrease of exchangeable Cd. Higheractive Si and pH, as well as lower Eh, were also responsible for the reduction of exchangeable Cd. Cd boundto Mn oxide was positively correlated with pH values and rose significatly after one-month incubation, butdecreased after three-month incubstion. Cd bound to amorphous Fe oxide increased with the incubationtime, but was not effected significantly by adding organic materials.展开更多
Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive ...Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive at robust generalizations about processes and mechanisms structuring island biotas, it is important to examine under-represented taxa such as snakes for the insights they may offer. We tested for the existence of nestedness and underlying causal mechanisms using snake data collected on islands in the Thousand Island Lake, China. We used the line-transect method to survey snake occupancy and abundance on 20 islands during two breeding seasons in 2009 and 2010. We used the recently developed metric WNODF to estimate nestedness. We used Spearman rank correlations to examine the associations of nestedness and habitat variables （area, isolation, and habitat diversity） as well as life-history traits （body size, clutch size, geographical range size and area requirement） related to species extinction and immigration tendencies. Snake assemblages were significantly nested and were shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of snake assemblages was not due to passive sampling or selective colonization. From a conservation viewpoint, our results indicate that we should protect both the largest island with the most species-rich community and habitat-rich islands to maximize the number of species preserved .展开更多
The small-island effect （SIE） has become more and more part of the theoretical framework of island biogeography and biodiversity research. However, previous methods for the detection of SlEs are often flawed in one ...The small-island effect （SIE） has become more and more part of the theoretical framework of island biogeography and biodiversity research. However, previous methods for the detection of SlEs are often flawed in one way or another, including not accounting for model complexity, not comparing all relevant models, and not including islands with no species. Therefore, the existence and the prevalence of the SIE may be dubious. In this study, after controlling for all these methodological shortcomings, we tested for the existence of the SlE in amphibian assemblages on subtropical landbridge islands created by the inundation of the Thousand Island Lake, China. We used the line transect method to determine the distribution of amphibian assemblages on 23 study islands during 3 breeding seasons from 2009 to 2011. To evaluate whether an SIE exists in amphibian assemblages, we compared the fit of a simple linearized power model with two most widely used breakpoint regression models. The information-theoretic multimodel inference approach based on Akaike＇s information criterion identified the left-horizontal SIE model as the best single model. Thus, we found strong evidence for the existence of an SIE in our system. The upper limit of the SlE for amphibian assemblages was 39.95 ha. Below this threshold area, amphibian richness varied independently of island size. The SlE in amphibian assemblages may be due to episodic disturbances, stochastic events, and nutrient subsidies from the lake. Our results indicate that all the islands 〉39.95 ha should be protected for the effective conservation of amphibian assemblages in our system.展开更多
Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex ...Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.展开更多
基金Supported by the Innovation Project of CAS (No.KZCX2-YW-426)a Provincial Project of Hubei (No. 2006AA305A0402)the National Basic Research Program of China (973 Program, No. 2002CB 412306)
文摘In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorurn, but no significant effect is found in this study.
文摘The effect of three organic materials (rice straw, Chinese milk vetch and pig manure) on the fractionationof cadmium added into two soils (a red soil and a fiuvo-aquic soil) was studied using submerged incubationexperiment. The organic materials increased soil solid organic carbon (SOC), pH value, the concentration ofactive Si in all the treatments and active Fe and Mn in some treatments. Accumulated SOC caused directlythe increase of Cd bound to solid organic matter and consequently the decrease of exchangeable Cd. Higheractive Si and pH, as well as lower Eh, were also responsible for the reduction of exchangeable Cd. Cd boundto Mn oxide was positively correlated with pH values and rose significatly after one-month incubation, butdecreased after three-month incubstion. Cd bound to amorphous Fe oxide increased with the incubationtime, but was not effected significantly by adding organic materials.
基金We thank two anonymous reviewers for helpful comments on earlier version of the manuscript. We are grateful to Chunan Forestry Bureau and the Thousand Island Lake National Forest Park for permits necessary to conduct the research. This study was supported by the National Natural Science Foundation of China （Nos. 31100394, 31170397）, the China Postdoctoral Science Foundation （No. 20070411192）, Zhejiang Provincial Postdoctoral Science Foundation, and the Fundamental Research Funds for the Central Universities.
文摘Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive at robust generalizations about processes and mechanisms structuring island biotas, it is important to examine under-represented taxa such as snakes for the insights they may offer. We tested for the existence of nestedness and underlying causal mechanisms using snake data collected on islands in the Thousand Island Lake, China. We used the line-transect method to survey snake occupancy and abundance on 20 islands during two breeding seasons in 2009 and 2010. We used the recently developed metric WNODF to estimate nestedness. We used Spearman rank correlations to examine the associations of nestedness and habitat variables （area, isolation, and habitat diversity） as well as life-history traits （body size, clutch size, geographical range size and area requirement） related to species extinction and immigration tendencies. Snake assemblages were significantly nested and were shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of snake assemblages was not due to passive sampling or selective colonization. From a conservation viewpoint, our results indicate that we should protect both the largest island with the most species-rich community and habitat-rich islands to maximize the number of species preserved .
基金The study was supported by the National Natural Science Foundation of China （31471981, 31100394, and 31210103908）, the Project-sponsored by SRF for ROCS, SEM （J20130585） and the Fundamental Research Funds for the Central Universities （2016QNA6001 ）.
文摘The small-island effect （SIE） has become more and more part of the theoretical framework of island biogeography and biodiversity research. However, previous methods for the detection of SlEs are often flawed in one way or another, including not accounting for model complexity, not comparing all relevant models, and not including islands with no species. Therefore, the existence and the prevalence of the SIE may be dubious. In this study, after controlling for all these methodological shortcomings, we tested for the existence of the SlE in amphibian assemblages on subtropical landbridge islands created by the inundation of the Thousand Island Lake, China. We used the line transect method to determine the distribution of amphibian assemblages on 23 study islands during 3 breeding seasons from 2009 to 2011. To evaluate whether an SIE exists in amphibian assemblages, we compared the fit of a simple linearized power model with two most widely used breakpoint regression models. The information-theoretic multimodel inference approach based on Akaike＇s information criterion identified the left-horizontal SIE model as the best single model. Thus, we found strong evidence for the existence of an SIE in our system. The upper limit of the SlE for amphibian assemblages was 39.95 ha. Below this threshold area, amphibian richness varied independently of island size. The SlE in amphibian assemblages may be due to episodic disturbances, stochastic events, and nutrient subsidies from the lake. Our results indicate that all the islands 〉39.95 ha should be protected for the effective conservation of amphibian assemblages in our system.
基金supported by Tsinghua University Initiative Scientific Research Program (Grant No. 2009THZ07060)the State Key Laboratory of Hydroscience and Engineering of Tsinghua University (Grant No. 2010-TC-2,2009-TC-2)
文摘Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.
