Plant autotoxicity widely exists in natural and agricultural ecosystems.Based on the hormetic dose responses of plants to autotoxins,this study introduced the Mitscherlich limiting-factor model into the An-Johnson-Lovett hormesis model and established a new autotoxicity dose/response model.Illustration of the model is in a good agreement with the literature.It demonstrates that the new model has better described the mechanisms of autotoxic phenomenon from the point view of ecological limiting-factor.The new model may be a good tool for analysing autotoxicity data as well as a platform for further research on plant autotoxicity.
Using Hegyi's competition index model for individual tree,we analyzed the intraspecific and interspecific competition of Picea wilsonii in Liancheng National Nature Reserve of Gansu.The results showed that intraspecific competition intensity of Picea wilsonii reduced with the increase in diameter scale of the trees.The intraspecific competition was much larger than interspecific competition.The order of competition intensity(CI.) was listed as:Picea wilsonii>Populus davidiana>Acer tetramerum var.betulifolium>Pinus tabulaeformis>Salix sp.>Betula albo-sinensis.The relationship between competition intensity and individual growth of objective tree followed closely the following equation CI.= AD–B.When the diameter scale reached to 40 cm,there was little change of competition intensity.The CI.of Picea wilsonii was positively correlated with altitude.
Four filamentous cyanobacteria strains Oscillatoria cortiana,Oscillatoria acuminate,Oscillatoria anguina and Leptolyngbya foveolara in freshwater were studied under laboratory conditions.Experiments were performed to determine their growth in the presence of a wide range of concentrations of nitrogen and phosphorus.The results showed that O.cortiana and L.foveolara had a greater adaptability to survive in high concentration of nitrogen or phosphorus than the others,and they grew well with a concentration of NO3--N from 0.016 to 2.0 mg·mL-1 or phosphorus ranging from 1.36 to 13.6 μg·mL-1.Growth of four strains was inhibited under the condition in which only NH4+-N was supplied.
The genetic toxicology of blue-green algae filtrate of Tai Lake was investigated using micronucleus test of root tip cell of Vicia faba and Allium sativum L..The results showed that in contrast to negative control(pure water),the effects of other treatments on micronucleus(MCN) of two plant root cells were significantly increased except for those of eight times diluent of blue-green algae filtrate,and that the effects which induced micronucleus in root-tip cells of plant exhibited dose-effect.The effect of stock solution of blue-green algae filtrate on MCN of root tip cell of broad bean was significantly higher than that of positive control(0.8 mg·mL-1 cyclophosphamide).It can be concluded that there is strong genotoxicity in blue-green algae filtrate during blue-green algae fast growth in Lake Tai.
From June 2006 to December 2007,monthly samplings of 3 sites were carried out for measuring chlorophyll a concentration,composition and density of phytoplankton.Phytoplankton sampling yielded 65 taxonomic units(mostly to genus levels) in 53 genera.Microcystis aeruginosa was predominant with 92.23% of the total taxa.The average algal density for all the sites was 1.23×108 ind·L-1 and the maximum was 1.39×109 ind·L-1,while the minimum was 3.21×105 ind·L-1.With the increased distance between Dianchi Lake and the sampling sites(from site 3 to 1),total density of phytoplankton and Microcystis aeruginosa decreased dramatically,while the Shannon-Wiener,Simpson(1/Dominance) diversity and evenness went up significantly.Besides,Microcystis aeruginosa of site 2 and 3 was similar with that of Dianchi Lake,while site 1 was different from site 2 and 3 due to its long distance away from Dianchi Lake,indicating significant impacts of Dianchi Lake water on taxonomic composition of site 2 and 3.From the percentage similarity index of community(PSc) among 3 sites,we found that PSc index between site 1 and 3 was significantly lower than that of site 1&2 and site 2&3.Except for April,May and July 2007,the PSc index between site 2 and 3 was higher than 60%.After the project operation,Microcystis aeruginosa of site 1 and 2 showed decreasing trend.Nevertheless,Microcystis aeruginosa of site 3 increased.At the same time,species richness of the 3 sites increased dramatically after the project.Changes in algal community structure(i.e.,the species present and their relative abundances) following project operation were evaluated by non-metric multi-dimensional scaling(NMS) ordinations.The results showed that overall algal assemblage structure of the 3 sites remained similar throughout the study period(MRPP,p>0.05),indicating no significant impacts on phytoplankton community 1-year after project operation.
Due to the difference in water volume,seasonal dynamics and structure of the phytoplankton community in small reservoirs are distinct from those in large reservoirs.To understand the composition and dynamics of the phytoplankton community in small reservoirs,we investigated a typical small oligotrophic reservoir located in southern China,Gida Reservoirs,in April,August and December,2006.The concentrations of TN,TP were low in this reservoir.32 taxa of phytoplankton were,in total,identified from 3 samplings.The abundance of phytoplankton ranged from 69 to 342cells·mL-1,and the biomass of phytoplankton ranged from 1.34 mg·L-1 to 3.69 mg·L-1.Cells abundance and biomass of phytoplankton in the summer were higher than in winter and spring.Peridinium sp.was the first dominant group of biomass and abundance in the phytoplankton community.In the summer,the abundance of Cryptomonas sp.and Cosmarium spp.increased and became the dominant species.In the winter,phytoplankton abundance and biomass decreased significantly.Cryptomonas sp.was out of the samples,and Aulacoseira granulate,following Peridinium sp.,became one of the dominant species.As a small reservoir with a small catchments,the thermal structure is stable for a whole year,and rainfall functions the main source of nutrients.The thermal stability favors Peridinium to be the dominant species,and precipitation is the principle driving force for the seasonal dynamics of the phytoplankton community.
The pot experiment was conducted to study the inoculation effects of nitrogen-fixing bacteria(Phy),or/and phosphate-solubilizing bacteria(Vib) on the growth and nutrients uptake of Rhizophora stylosa seedlings.The growth indexes of seedlings were assessed 6 months after inoculation.Statistic analysis revealed that either Phy or Vib inoculation could improve the nutritional status,enhance photosynthesis,and stimulate the growth of seedlings(with the increase of height,ground diameter,and biomass).Dual inoculation of Phy and Vib yielded the highest plant dry weight and nutrient uptake compared to the single inoculation.Dual inoculation of Phy and Vib increased plant dry height,diameter,underground biomass,total biomass,total nitrogen of roots,total phosphorus of roots and total chlorophyll content of leaves by 43.3%,11.6%,44.8%,29.9%,29.3%,27.0% and 16.8% compared to the uninoculated plant,respectively.Dual inoculation shows some positive interaction on the growth of R.stylosa seedlings,and has great potential for inoculation at seedling stage.
Hydrogenase from Synechococcus sp.PCC 7942 was purified to close homogeneity aerobically at room temperature.The hydrogenase-containing crude extract was collected after ultrasonic disruption and removal of cell debris by ultracentrifugation.Subsequently,three steps of column chromatographies(anion exchange,hydrophobic interaction and gel filtration)were performed.Hydrogenase was purified about 218-fold with a yield of 6.5% finally.The purified enzyme has a specific activity for hydrogen evolution of 1.46 U·mg-1 protein.SDS-PAGE gel of the purified enzyme revealed five predominant protein bands with estimated molecular weights of 83,60,47,30 and 27 kDa,respectively.The enzyme is a soluble bidirectional hydrogenase and shows maximum activity while using reduced methyl viologen as an electron donor.The optimum temperature and pH value for hydrogen evolution catalyzed by the purified hydrogenase are 50℃ and pH 8.0.
According to water quality pollution level of Huadi River in Guanazhou,we analyzed the status of SD,chlorophyll a,phytoplankton and zoobenthos in the waterbody.The results indicated that the dominant phytoplankton were cyanophytes which were contaminative-resistant habit and proliferated in the waters.The density of Limnodrilus sp.contaminative-resistant of zoobenthos increased yearly,and the concentration of TP and TN also increased year after year.Besides,the pollution resulted from organic matter became more serious.The self-purification capacity of Huadi River can't treat the pollution by itself,so related government departments should attach importance to integrated environmental control.This paper pertinently advised that we should take effective measures which combine ecological theories and multi-side co-operation to control the pollution in Huadi River.
The communities and biodiversities of zooplankton,including species composition,density,biomass and biodiversity index were studied at four sampling stations in Xin River(1#,2#) and QianTang River(3#,4#) of Ningbo from December 2007 to January 2008.24 species of zooplankton were found.Brachionus calyciflorus dominated in Rotifera,and Mesocyclops leuckarti dominated in Crustacea.There were more species of zooplankton in stations 1#and 3# than those in stations 2# and 4#,and so were the biomass and biodiversity index.ANOVA results showed that there were significant differences of Brachionus calyciflorus density and biodiversity index of zooplankton in the four different sampling stations(p<0.05.) Multiple comparison showed that obvious differences of Brachionus calyciflorus density could be observed between 1# and 2#,1# and 4#(p<0.20).There were obvious differences of rotifers biodiversity index between 3# and 4#(p<0.20),and so were the biodiversity index of Crustacea between 1#and 4#,1# and 2#,3# and 4# respectively(p<0.20).
The niche breath of Aphis citricota and Tetranychus viennensis were more than other pests in U.S.apricot and plum orchard,those are dominant population occupying more space;Resources of natural enemies were rich and majority was Chrysopa septempenctata;Pests had strong competition,natural enemies were so.Natural enemies and major pests could meet very often.They had strong pursuing and control effect to Aphis citricota and Tetranychus viennensis from time dimension.The follow orders of the number of main natural enemies and main pests Aphis citricota was chrysopidaes>Propylaea japonica>araneidas>Leis axyridis>other coccinellidaes>syrphidaes>Coccinel laseptem punctata>Hippodamia variegata.The fuzzy neartude of chrysopidae and Propylaea japonica were highest than others,that two and Aphis citricota have the highest relations of same domain,and stong to pursue Aphis citricota,to inhibit the number of Aphis citricota.
Guoluo Tibetan Autonomous Prefecture,located in the Yellow River Headwaters region,is one of prefectures with the highest altitude,the worst climate,the most difficult environment,the least socio-economic development and the highest proportion of mono-ethnic composition in China.The ecological environment is very sensitive and fragile and the ecological problems become increasingly serious,which have posed a bad impact on the local socio-economic development and the ecological environment,as well as people's property safety of the middle and lower reaches of Yellow River.Based on the data of 2006 Landsat7 ETM image,by use of RS and GIS,the landscape pattern of Guoluo Tibetan Autonomous Prefecture was analyzed.The corridor effect of the Yellow River was obvious when in 10 kilometers and had a scale restriction.Finally,the ecological functions of county zone were concluded according to ecological suitability.And also some management measures about the ecological planning were suggested.This study provided a strong theoretical and technical basis for the region's ecological protection policy formulation and scientific environmental management.
From the gradient spatiotemporal landscape pattern analysis using the landscape metrics based on the 1990 and 2000 land use data of Beijing metropolitan region,we achieved the affirmative and informative conclusions on the characteristics of Beijing's landscape structure change pattern and the land use spatiotemporal change pattern in the ten years.Forest and cultivated land were the most two dominant landscape types,but the urban land expanded largely from 1990 to 2000 and the total area of urban land was almost the same as rural settlement which indicated that the urbanization level of Beijing had reached to a high level.The urban land proportion decreased as the distance from the city center increased and urban areas expanded to the suburban areas in the ten years.The urbanization degree was higher to the north direction than to the south.The cultivated land area decreased in all blocks in the transects and the edge areas of the city were the most dynamic area and they were more separated and fragmented.Combining landscape metrics with gradient analysis from a temporal angle is a robust and efficient method to study the landscape pattern change in the process of urbanization.
The forest ecosystem service in Liu-Xi River Forest Farm was evaluated by market valuation method,shadow engineering method,substitute expense method and so on.The results showed that the total value of the ecosystem service was estimated up to 6.18×108 yuan·a-1,and that the main value of ecosystem service was indirect value and the most value was water reservation.The value of each service was as follow:the timber was worth 6.03×107 yuan·a-1;water reservation was worth 4.50 ×108 yuan·a-1;soil conservation was worth 1.46×107 yuan·a-1;carbon fixation and oxygen release was worth 5.80×107 yuan·a-1;air purification was worth 2.42×107 yuan·a-1;eco-tourism was worth 3.00×106 yuan·a-1,and biodiversity maintenance was worth 7.61×106 yuan·a-1.
Arbuscular mycorrhizal fungi are soil microbes widely existing in ecosystems that can develop symbiosis with most of the terrestrial plants.In recent years,their important roles on protecting host plants against biotic and abiotic stresses have gradually been concerned.This article reviewed the effects of arbuscular mycorrhizal fungi on host plants under abiotic stresses(heavy metal contamination,organic pollution,high salinity and drought)and biotic stresses(pathogen and nematodes infection).Finally,the future research direction in this field was put forward.
Fish with most species of vertebrates widely distributes in various water bodies,and holds rich genetic diversity,which plays an important role in survival and evolution of fish.However,fish genetic diversity is seriously affected by various natural and artificial factors in recent years.The researches on present situation of fish genetic diversity by means of molecular markers can lay the foundation for fish genetic breeding,molecular evolution researches and protection of fish genetic resources.Nowadays,the molecular markers including mtDNA,have been applied to studying genetic structure of fish populations and the relationship between the genetic structure and related factors.In the present review,we reviewed the structure,genetic characteristics of mtDNA and its application to the molecular population genetics of fish.
Fertilization and irrigation are two main practices in daily maintenance of turfgrass and they play as safeguard in achieving high-quality turf.In this article,issues of recent years that raised the most concern in fertilization and irrigation of turfgrass were reviewed,including the response of turfgrass under the application of N,P,K and the combinations,as well as the influence of turfgrass growth on which the frequency and amount of irrigation act.The best strategy to fertilize and irrigate turfgrass was also discussed.And the co-working relationship between these two applications was illustrated.Researches aimed at how fertilization and irrigation influence the growth of turfgrass were summarized in this article in order to provide adequate reference when it comes to planning a turfgrass fertilization and irrigation,water conservation,reduction of negative effect upon which fertilization acts,and acquiring an ideal turf.
Five domains of the research on forest landscape ecology in China were reviewed:the analysis of forest landscape pattern and the influencing factors,the ecological transformation,planning and evaluation of forest landscape,the construction of dynamic models and decision-making models and the edge effect and dynamics of forest landscape,and the biodiversity conservation on the level of landscape.For promoting sustainable development of forest landscape ecology and effective management of forest resource,the main problems of current research on forest landscape ecology in China were summarized.Finally,the authors proposed what challenges the forest landscape ecology in China met with and the future main dynamic directions on forest landscape ecology.
