两种一枝黄花属植物化感作用的初步研究

本研究测定了加拿大一枝黄花和本地一枝黄花新鲜茎叶的水浸液对本地植物的化感作用,分析了两种一枝黄花不同浓度浸提液对绿豆、花菜、萝卜、莴苣、小麦幼根生长的影响。试验结果表明:在相同水浸液浓度下,加拿大一枝黄花对本地植物的化感抑制作用均强于本地一枝黄花,且随着水浸液浓度的升高,加拿大一枝黄花对受体植物的抑制作用明显增强。

Characteristics of soil microbial community functional and structure diversity with coverage of Solidago Canadensis L

The relationship between Solidago canadensis L. invasion and soil microbial community diversity including functional and structure diversities was studied across the invasive gradients varying from 0 to 40%, 80%, and 100% coverage of Solidago canadensis L. using sole carbon source utilization profiles analyses, principle component analysis （PCA） and phospholipid fatty acids （PLFA） profiles analyses. The results show the characteristics of soil microbial community functional and structure diversity in invaded soils strongly changed by Solidago canadensis L. invasion. Solidago canadensis L. invasion tended to result in higher substrate richness, and functional diversity. As compared to the native and ecotones, average utilization of specific substrate guilds of soil microbe was the highest in Solidago canadensis L. monoculture. Soil microbial functional diversity in Solidago canadensis L. monoculture was distinctly separated from the native area and the ecotones. Aerobic bacteria, fungi and actinomycetes population significantly increased but anaerobic bacteria decreased in the soil with Solidago canadensis L. monoculture. The ratio of cyl9：0 to 18：1 co7 gradually declined but mono/sat and fung/bact PLFAs increased when Solidago canadensis L. became more dominant. The microbial community composition clearly separated the native soil from the invaded soils by PCA analysis, especially 18： lco7c, 16： lco7t, 16： lco5c and 18：2co6, 9 were present in higher concentrations for exotic soil. In conclusion, Solidago canadensis L. invasion could create better soil conditions by improving soil microbial community structure and functional diversity, which in turn was more conducive to the growth ofSolidago canadensis L.

Co-invasion of daisy fleabane and Canada goldenrod pose synergistic impacts on soil bacterial richness

Understanding the impacts of co-invasion of multiple invaders on soil bacterial communities is significant in understanding the mechanisms driving successful invasion.This study aimed to determine the response of soil bacterial communities to co-invasion of two invaders daisy fleabane(Erigeron annuus)and Canada goldenrod(Solidago canadensis).Daisy fleabane and/or Canada goldenrod invasion significantly enhanced the operational taxonomic unit richness,Shannon index,and Chao1 index of soil bacterial communities.Canada goldenrod under light degree of invasion and co-invasion of daisy fleabane and Canada goldenrod regardless of invasion degree signally improved the ACE index of soil bacterial communities.Thus,the two invaders can enhance soil bacterial diversity and richness to facilitating subsequent invasion due to the fact that higher soil bacterial diversity and richness can enhance the levels of soil function and nutrients acquisition of plant species.ACE index of soil bacterial communities subjected to co-invasion of daisy fleabane and Canada goldenrod regardless of invasion degree was greater than that under the independent invasion of either daisy fleabane or Canada goldenrod.Hence,co-invasion of the two invaders can impose synergistic impacts on soil bacterial richness,which may build a preferable soil micro-environment via the intensified soil bacterial communities,which is contributive to their following invasion.

Volatile Constituents of Juniperus communis L., Taxus canadensis Marshall. and Tsuga canadensis （L.） Carr. from Canada

The essential oil composition leaves of Juniperus communis L., Taxus canadensis Marshall. and Tsuga canadensis （L.） Carr. from Canada were investigated by head space solid phase microextraction （HS-SPME） and gas chromatography/mass spectrometry （GC-MS）. Thirty-three, thirty and thirty-one components were identified representing 95.78%, 93.89%, 96.14% of the oil, respectively. Limonene （26.12%）, benzene （15.62%）, 13-mrycene （9.08%） and β-pinene （7.30%） were found to be the main constituents of J. communis; 1-propanone （36.38%）, morpholine （10.95%）, methylamine （9.10%） and methanone （8.14%） were detected main components of Taxus canadensis; bornylacetate （26.84%）, α-pinene （23.74%）, camphene （11.93%） and limonene （6.02%） were determined as major constituents of Tsuga canadensis. The chemical distributions of the essential oil compounds in the genus pattern were discussed in means of chemotaxonomy and natural products.

Nitrogen addition increased resistance of resident plant community to Solidago canadensis invasion by altering allelopathic effect

Allelopathy plays an important role in the interaction between invasive and resident plants.Atmospheric nitrogen(N)deposition has become a global problem,but it is unclear whether N enrichment affects the interaction between invasive and resident plants by affecting their allelopathy.Thus,we performed a greenhouse experiment in which the resident plant community was grown under two levels of invasion by S.canadensis(invasion vs.no invasion)and fully crossed with two levels of allelopathy(with or without adding activated carbon)and two levels of N addition(with or without).The resident plant communities were constructed with eight herbaceous species that often co-occur with S.canadensis.The results showed that both allelopathy of S.canadensis and the resident plants had obvious positive effects on their own growth.Nitrogen addition had more obvious positive effects on the resident plants under invasion than those that were not invaded.Moreover,N addition also altered the allelopathy of resident plants.Specifcally,N addition improved the allelopathy of resident plants when they were invaded but decreased the allelopathy of resident plants when they grew alone.Although nitrogen addition had no obvious effect on S.canadensis,it reduced the allelopathy of S.canadensis.These results suggest that N addition could improve the resistance of resident plants to invasion by improving the allelopathy of resident plants and reducing the allelopathy of S.canadensis.These fndings provide a scientifc basis to manage and control the S.canadensis invasion.

Interactive effect of climate warming and nitrogen deposition may shift the dynamics of native and invasive species

Aims Projections of invasive species expansion under a warmer world often do not explicitly consider the concurring nitrogen(N)deposition.It remains largely unknown how the convoluted effect of climate warming and N deposition will shift the native and invasive species dynamics.Here,we hypothesize that the concurring in creases in N and temperature would promote growth of invasive species greater than that of native species.Methods A controlled greenhouse experiment was conducted to quantify the growth response of an invasive species(Solidago canadensis L.)and a co-existing native species(Artemisia argyi Levi,et Van)under the effects of climate warming,N deposition and their interactions.Important Findings Due to the strong positive effect of N addition,the interactive effect of temperature increase and N addition resulted in an overall significant increase in growth of both in vasive and native species,demonstrating that these manipulations may make microhabitats more favorable to plant growth.However,the relative increases in biomass,height and diameter of invasive S.canadensis were signifiesntly lower than those of native A.argyi.This suggests that the vegetative growth superiority of invasive S.canadensis over the native species A.argyi is reduced by the enhanced N availability in the warmer world.Therefore,the inclusion of N deposition may mitigate the projection of invasive species S.canadensis expansion under climate warming.

Inhibitory effects of the extracts with different solvents from three compositae plants on cyanobacterium Microcystis aeruginosas

The algicidal activity of the terrestrial plants is a novel and promising means for alga control of eutrophic waters. In this study, three compositae plants-Artemisia annua （A. annua）, Conyza canadensis （ C. canadensis）, and Erigeron annuus （E. annuus） were selected and antialgal activity of petroleum ether （PE）, ethyl acetate （EA） and ethanol extracts of these plants on blue algae Microcystis aeruginosa was investigated. The result shows the EA extracts of these plants present the stronger inhibitory effects. The results of the further separation of PE and EA extracts according to water-solubility and acidity or alkalinity show that fatty acids and telpenoids in A. annua, terpenoids and organic acid in C. Canadensis and E. Annuus may be the main antialgal active constituents. This study suggested that the EA extracts of these plants could become the potential algicide to prevent water blooming.

Effects of latitude and soil microbes on the resistance of invasive Solidago canadensis to its co-evolved insect herbivore Corythucha marmorata

There is an increasing likelihood that invasive plants are again exposed to their co-evolved specialist herbivores in the non-native range.However,whether there is a latitudinal pattern associated with the resistance of an invasive plant to its co-evolved herbivores and how soil microbes affect resistance has been little explored.We hypothesized that the resistance of invasive Solidago canadensis to its co-evolved insect herbivore Corythucha marmorata could increase with latitude,and that local rhizosphere microbes could facilitate invasive plants to become resistant to their co-evolved herbivores.We conducted a field survey and a greenhouse experiment to examine whether there was a latitudinal pattern in the abundance of C.marmorata and in the damage it caused to S.canadensis in China.We tested whether local rhizosphere microbes of invasive plants can promote the resistance of S.canadensis to C.marmorata herbivory.In the field survey,both density of C.marmorata and damage level of S.canadensis were positively correlated with latitude,and with S.canadensis plant growth,indicating a latitudinal pattern in the resistance of S.canadensis to C.marmorata.However,in the greenhouse experiment,S.canadensis from different latitudes did not suffer significantly from different levels of damage from C.marmorata.Additionally,the damage level of S.canadensis was lower when rhizosphere soil and rhizomes originated from field S.canadensis with same damage level than with different damage levels.This result indicates that local rhizosphere soil microbes promote the adaptation of S.canadensis to resistance of C.marmorata.

Soil Respiration and Litter Decomposition Increased Following Perennial Forb Invasion into an Annual Grassland

Exotic plant invasions may alter ecosystem carbon processes, especially when native plants are displaced by plants of a different functional group. Forb invasions into grasslands are common, yet little is known about how they impact carbon cycling. We conducted a field study over 2 years from April 2010 to March 2012 in China to examine changes in soil respiration （Rsoil） following invasion of exotic perennial forb species （Alternanthera philoxeroides or Solidago canadensis） into an annual grassland dominated by a native annual graminoid （Eragrostis pilosa）. Measurements of Rsoil were taken once a week in stands of the native annual graminoid or one of the forb species using static chamber-gas chromatograph method. Aboveground litterfall of each of the three focal species was collected biweekly and litter decomposition rates were measured in a 6-month litterbag experiment. The monthly average and annual cumulative Rsoil increased following invasion by either forb species. The increases in cumulative Rsoil were smaller with invasion of Solidago （36%） than Alternanthera （65%）. Both invasive forbs were associated with higher litter quantity and quality （e.g., C：N ratio） than the native annum graminoid. Compared to the native annual graminoid, the invasive forbs Altevnanthera （155%） and Solidago （361%） produced larger amounts of more rapidly decomposing litter, with the litter decay constant k being 3.8, 2.0 and 1.0 for Alternanthera, Solidago and Eragrostis, respectively. Functional groups of the invasive plants and the native plants they replaced appear to be useful predictors of directions of changes in Rsoil, but the magnitude of changes in Rsoil seems to be sensitive to variations in invader functional traits.

Substrate availability regulates the suppressive effects of Canada goldenrod invasion on soil respiration

Invasive alien plants not only decrease riparian vegetation diversity but also alter wetland ecosystem carbon processes,especially when they displace the original vegetation.Invasive Canada goldenrod(Solidago canadensis L.)has colonized large areas of disturbed and undisturbed land in southeastern China,yet little is known regarding how it affects soil carbon cycling.To explore the response patterns of soil respiration following S.canadensis invasion and their driving mechanisms,an observational field study and a greenhouse experiment simulating invasion were performed.In the field study,soil respiration was measured weekly from 21th July 2018 to 15th December 2018.In the greenhouse experiment,soil,autotrophic and heterotrophic respiration were measured every 1st and 15th of the month from 15th July 2019 to 15th December 2019.Soil,autotrophic and heterotrophic respiration were measured using a closed-chamber system with the deep gauze collar root exclusion method.Solidago canadensis invasion appeared to decrease the total soil CO_(2) emissions in both the field study and the greenhouse experiment.The suppressive effects on soil respiration may be attributed to S.canadensis invasion-induced alterations in the quality and quantity of available soil substrate,suggesting that S.canadensis invasion may impact soil carbon cycling via plant-released substrates and by competing for the soil available substrate with native plant and/or soil microbes.These results have substantial implications for estimations of the effects of invasive plants on belowground carbon dynamics and their contribution to the warming world.

Effects of arbuscular mycorrhizal fungi on Solidago canadensis growth are independent of nitrogen form

Aims Invasive plants may alter soil fungal communities in a way that improves their growth.Nitrogen(N)content of soil affects the symbiosis between plants and arbuscular mycorrhizal fungi(AMF),further determining plant growth.Yet,it is unclear whether altered AMF communities change the dependence of invasive and native species on N-form,and whether N forms alter the invasive plant–AMF interaction(PSIM).Methods Two synthetic plant communities,including four Solidago canadensis individuals and four native plant species,were inoculated with AMF spores from S.canadensis-invaded soils and adjacent non-invaded soils,and were provided with nitrate,ammonia or glutamate.After their growth,the performance of the two plant communities in treatments of AMF origin and N forms,and the pathways of the N forms affecting S.canadensis growth and PSIM were evaluated.Important Findings Solidago canadensis had no obvious N-form dependence in any of the AMF inoculations.Native plant species showed weak N-form dependence,but invasive AMF could remove their N-form dependence.In the absence of N,AMF did not affect growth of S.canadensis and the native plants.In contrast,with N addition,invasive AMF significantly increased belowground and total biomass of the invasive plants but not those of the native plants.Positive PSIM of S.canadensis was also evidently greater than that of native plant species and was realized through directly or indirectly regulating phenotypic traits including plant height,leaf number and number of rhizomes.Our findings emphasize the importance of plant–AMF interactions and a unique N-acquisition strategy during plant invasions.