河湖水沙对磷迁移转化的作用研究进展

泥沙颗粒对水体中的磷具有较好的亲和能力,河湖中的水沙运动可以改变磷的赋存状态并在一定条件下造成水体富营养化等生态环境问题。综合近年研究成果,目前关于河湖泥沙对磷的迁移转化作用研究存在研究内容局限、作用机理分歧、数学模型不全面等问题,且多为宏观层面研究。有必要在实验技术创新的基础上探讨水沙微界面吸附,并结合生态作用完善复杂条件多因子耦合对泥沙迁移转化磷的理论研究。

Overview of Pharmacological & Ecological Research of Scirpus tabernaemontani Gmel

On the basis of extensive literature search, the species, ingredients, pharmacology, clinical applications, ecological value and cultivation techniques of Scirpus tabemaemontani Gmel have been reviewed, to provide scientific data for further research ＆ development.

Effects of Compound Probiotics on Intestine and Intestinal Aeromonas hydrophila of Fish

[Objective] This study was conducted to develop compound probiotics that can be used as the alternatives of chemical drugs and antibiotics in aquaculture. [Method] Different concentrations of EM （effective microorganisms） and Bacillus amyloliquefaciens were mixed at a ratio of 1：1, and sprayed on fish feed. The growth of intestinal villi of the fishes that had been fed with the feed mixed with compound probiotics for three months was observed; meanwhile, the content of in- testinal Aeromonas hydrophila was detected by real-time quantitative PCR. ｜Result] The compound probiotics promoted the development of intestinal villi, and inhibited the growth of A. hydrophila, and the effects were also concentration dependent. However, the compound probiotics did not increase the thickness of the intestinal serous layer, muscular layer and submucosal layer. [Conclusion] The compound probiotics we prepared can be used and popularized in aquiculture as it can inhibit the growth of A. hydrophila.

Interactions between a cyanobacterial bloom (Microcystis) and the submerged aquatic plant Ceratophyllum oryzetorum Kom.

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.

Changes in niche differentiation and environmental filtering over a hydric stress gradient

Aims Diversity in communities is determined by species’ability to coexist with each other and to overcome environmental stress that may act as an environmental filter.Niche differentiation(ND)results in stronger intra-than interspecific competition and promotes coexistence.Because stress affects interactions,the strength of ND may change along stress gradients.A greater diversity of plant growth forms has been observed in stressful habitats,such as deserts and alpine regions,suggesting greater ND when stress is strong.We tested the hypothesis that niche differences and environmental filters become stronger with stress.Methods In a semiarid grassland in southern Mexico,we sowed six annual species in the field along a hydric stress gradient.Plants were grown alone(without interactions),with conspecific neighbors(intraspecific interactions)or with heterospecific neighbors(interspecific interactions).We analyzed how the ratio of intra-to interspecific competition changed along the gradient to assess how water availability determines the strength of ND.We also determined if hydric stress represented an environmental filter.Important Findings We observed stronger intra-than interspecific competition,especially where hydric stress was greater.Thus,we found ND in at least some portion of the gradient for all but one species.Some species were hindered by stress,but others were favored by it perhaps because it eliminates soil pathogens.Although strong ND was slightly more frequent with stress,our species sample was small and there were exceptions to the general pattern,so further research is needed to establish if this is a widespread phenomenon in nature.

Leaf and Ecosystem Gas Exchange Responses of Buffel Grass-Dominated Grassland to Summer Precipitation

Sporadic rain events that occur during summer play an important role in the initiation of biological activity of semi-arid grasslands.To understand how ecosystem processes of a buffel grass(Cenchrus ciliaris L.)-dominated grassland respond to summer rain events,an LI 6 400 gas exchange system was used to measure the leaf gas exchange and plant canopy chambers were used to measure net ecosystem CO2exchange(NEE) and ecosystem respiration(Reco), which were made sequentially during periods before rain(dry) and after rain(wet). Gross ecosystem photosynthesis(GEP) was estimated from NEE and Reco fluxes, and light use efficiency parameters were estimated using a rectangular hyperbola model. Prior to the monsoon rain, grassland biomass was non-green and dry exhibiting positive NEE(carbon source) and low GEP values during which the soil water became increasingly scarce. An initial rain pulse(60 mm) increased the NEE from pre-monsoon levels to negative NEE(carbon gain) with markedly higher GEP and increased green biomass. The leaf photosynthesis and leaf stomatal conductance were also improved substantially. The maximum net CO2uptake(i.e.,negative NEE) was sustained in the subsequent period due to multiple rain events. As a result, the grassland acted as a net carbon sink for 20 d after first rain. With cessation of rain(drying cycle), net CO2 uptake was reduced to lower values. High sensitivity of this grassland to rain suggests that any decrease in precipitation in summer may likely affect the carbon sequestration of the semiarid ecosystem.