Alleopathic Effect Of Exotic Spartina Alterniflora On Native Plants And Arbuscular Mycorrhizal Fungi In Jiuduansha Wetland

In this study, exotic Spartina alterniflora, native Phragmite australis and Scirpusmariqueter in Jiuduansha islands were researched. The allelopacthic effect of S. alternifloraacross three periods (invaded in2000,2004and2007) on S. mariqueter was studied todiscuss the mechanism of the invasion of S. alterniflora. And then provide some scientificexplaination to the serious invasion of S. alterniflora.All root and soil samples of Phragmite australis, Scirpus mariqueter, and Spartinaalterniflora collected in August and October,2012, January and April,2013and seeds of S.mariqueter, plant samples of different S. alterniflora were taken back to our library. Weinvestigated the occurrence of arbuscular mycorrhizal fungi in Jiuduansha Wetland in-situ.The indoor simulate experiments of the effect of aqueous extracts from S. alterniflora on seedgermination and seedling growth of test plants were conducted. And further their impact onphysical and biochemical indices of test plants’ seedlings was researched; also the impact ofwater extracts from S. alterniflora on arbuscular mycorrhizal fungi colonization and soilspore density. Meanwhile, we studied whether the effect of S. alterniflora changed with timesince invasion. At last we verified that whether arbuscular mycorrhizal fungi inoculationcould conducive to the coordination among different plant species. The results were asfollows:(1) Arbuscular mycorrhizal fungi did exist in Jiuduansha Wetland, and the invasive S.alterniflora which was not rely on arbuscular mycorrhizal fungi was almost no AMFconolization. The AMF colonization of reed (Phragmite australis) could reach more than75%and AMF colonization of reed grown in the mixture communities with reed and S. alterniflorawas lower than that of single reed communities, which suggesting that S. alterniflorainhibited the AMF colonization of reed. Glomus and Acaulospora were the most abundantgenera in plant community soils. Differences of mycorrhizal fungi between seasons were notvery obvious.(2) Different concentrations of aqueous extracts from S. alterniflora all significantlyinhibited the germination of Lolium perenne L., Trifolium repens, and S. mariqueter (P<0.05), and the inhibitory effect enhanced with the increase of concentration. The inhibit effect onfinal germination, germination speed, length of seedling and root, fresh weight of test plantsreached maximum. Meanwhile, Some indicators of the performance of the test plants werepromoted at some low concentrations of S. alterniflora. And when aqueous extracts from S.alterniflora was0.05g ml-1, it slightly promoted the seed germination and seedling growthof L. perenne L.(P<0.05). The inhibition rate reached100%at the concentration of0.20g ml-1of T. repens.(3) The final seed germination of L. perenne L. was higher than that of T. repens, and theimpact of S. alterniflora water extracts on L. perenne L. was smaller than T. repens. Extractsof different plant parts had varied in allelopathic potential. The allelopathic potential ofupground part of S. alterniflora was stronger than that of underground part. And the highestinhibition came from stem extracts at0.2g ml-1. ANOVA analysis of variance showed thatmost leaf and stem water extracts could significantly influence the fresh weight of T. repens,indicating that seedlings of T. repens was vulnerable with adding S. alterniflora extracts.Meanwhile, the effects of S. alterniflora along different invasion time on seed germinationand seedling growth varied from each other (P<0.05). We found that the younger invasive S.alterniflora had stronger impact on seedling growth. S. alterniflora which containedsecondary compounds in water extracts did have allelopathic effects on seed germination andseedling growth of test plants, and the effect of invasive S. alterniflora might change alongwith time when it adapted to the local environment.(4) Based on the experiment above, we conducted cultivation in greenhouse withartificially constructed mycorrhizal fungi community inoculation and harvested for analysis.With non-inoculation with mycorrhizal and without adding S. alterniflora extracts being thecontrol groups, we measured mycorrhizal colonization and plant growth index. Theexperiment results showed that S. alterniflora water extract dosing significantly decreased themycorrhizal colonization, soil spore density, and plant growth (P<0.05). And the inhibitionincreased with the increasing concentration. The allelopathic effect varied among differenttypes of test plant species, showing that symbioses between T. repens and mycorrhizal fungiwas more sensitive to S. alterniflora. Extracts of three different S. alterniflora all influencedthe mycorrhizal symbiose, with the order of allelopathic effects on test plants being SB1<SB2<SB3. Meanwhile, mycorrhizal inoculation could help its host plants grow well inthe situation with adding S. alterniflora extracts.