| Arbuscular mycorrhizal fungi(AM fungi)play key roles in the maintenance of plant productivity,diversity and community stability of terrestrial ecosystem.In this study,we investigated the responses of composition and diversity of AM fungal spore to fertilization in Songnen grassland on the context of two plant communities characterized initially with low and high plant diversity during two growing seasons.Major conclusions were obtained as follows:(1)AM fungi were rich in Songnen grassland.Eight genus and twenty-eight species of AM fungi were identified from soil samples.There were 9 species belonging to Glomus,which accounted for 32.1% of the total AM fungi.And there were 5 species belonging to Acaulospora,4 species belonging to Rhizophagus,2 species belonging to Claroideoglomus and Funneliformis,1 species belonging to Sclerocystis,Septoglomus and Pacispora,respectively.Twenty-five species were identified and three species were unidentified.Funneliformis geosporum,Funneliformis mosseae,Glomus reticulatum and Claroideoglomus etunicatum were the dominant fungi in this study.(2)Impacts of fertilization on the characteristics of AM fungi varied among years,and two plant communities showed different responses to fertilization.N enrichment significantly increased the percentage of root colonization in both plant communities during 2014,while P enrichment decreased the percentage of root colonization.The hyphal length density was significantly decreased by N and P addition in plant community with low diversity during 2015,while fertilization did not influence the percentage of root colonization in both plant communities during 2014 and plant community with high diversity during 2015.Fertilization had no effects on the density and diameter of AM fungal spore.Moreover,AM fungi were suppressed successful by benomyl in both plant communities in terms of AM fungal colonization and colonization potential during two years.(3)The richness of AM fungal spore was significantly increased by nitrogen and phosphorus addition in plant community with low diversity during 2014.The richness of AM fungal spore was significantly reduced by nitrogen and phosphorus addition in plant community with high diversity during 2014,but not 2015.Neither nitrogen nor phosphorus had significant effects on the diversity of AM fungal spore as indicated by Shannon-Wiener,Simpson and Pielou index.AMF suppression enhanced AM fungal diversity in both plant communities during two years.(4)Results of the Pearson correlation analysis showed that soil physicochemical properties had direct effects on the characteristics of AM fungi in Songnen grassland.The characteristics of AM fungi were positively correlated with soil nutrient factors(soil total nitrogen,soil organic carbon),and negatively correlated with soil moisture,soil bulk density,soil electrical conductivity and pH value.The correlations among AM fungal characteristics and soil physicochemical properties were different between benomyl and no benomyl treatments,and the characteristics of AM fungal spore were closely related with soil physicochemical properties in plots with benomyl.In addition,there was less correlation among AM fungal characteristics and plant characteristics in both plant communities.(5)Results of MRPP and NMDS indicated that impacts of fertilization on the community composition of AM fungal spore varied among years,and two plant communities showed different responses to fertilization.N and P addition significantly affected the community composition of AM fungal spore in plots without benomyl within plant community with high diversity during 2014,while N addition significantly changed the community composition of AM fungal spore in plots without benomyl within plant community with low diversity during 2015.P addition significantly changed the community composition of AM fungal spore in plots with benomyl within plant community with low diversity during 2015.Moreover,benomyl significantly changed the community composition of AM fungal spore.(6)Results of NMDS indicated that the main factors influencing the community composition of AM fungal spore varied among years,and the responses of two plant communities were different.The community composition of AM fungal spore was significantly influenced by both soil physicochemical properties and plant characteristics during 2014.The community composition of AM fungal spore was significantly affected by soil electrical,pH value,total nitrogen,Simpson and Pielou index of plant community in plant community with low diversity during 2014.The community composition of AM fungal spore was affected by soil water content,Shannon-Wiener,Simpson and Pielou index of plant community in plant community with high diversity during 2014.Soil physicochemical properties had significant effects on AM fungal spore community,but it was not influenced by plant characteristics in 2015.In addition,the community composition of AM fungal spore was significantly affected by soil total nitrogen and pH value in plant community with low diversity during 2015,while the community composition of AM fungal spore was significantly affected by soil electrical and pH value in plant community with high diversity during 2015.In conclusion,AM fungi were rich in Songnen grassland.Nitrogen and phosphorus addition did not affect the AM fungal spore density,diversity index and the spore diameter significantly,but effects of fertilization on the community composition of AM fungal spore,the percentage of root colonization,the hyphal length density and spore abundance varied among years.Two plant communities with different diversity also showed different response to fertilization in terms of development characteristics and the community composition of AM fungal spore.The characteristics of AM fungi were positively correlated with soil nutrient factors(soil total nitrogen,soil organic carbon),but negatively correlated with soil water content,soil bulk density,soil electrical conductivity and pH value.We proposed that fertilization could improve the soil structure and contribute to the maintenance of the AM fungal diversity and community composition.The mycorrhizal technology would be applied to the restoration and rebuilding of degraded grassland in the Songnen Plain,leading to sustainable development of grassland ecosystem. |
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