| Ectomycorrhiza(ECM)is a form of symbiotic relationship that occurs between soil mycorrhizae and the roots of various plant species.Ectomycorrhizal hyphae do not penetrate their host's in cell walls.Ectomycorrhizas is distinguished from other fungi by forming a dense hyphal crust,called a mantle that surrounds the root surface.The hyphal network that extending into the surrounding soil could help the host plant to take up nutrients viz.,water and minerals,helping to effectively improve the survival rate of afforestation,promote plant growth in the adverse conditions like cold,drought and essential nutrients for soil health.Chinese pine(Pinus tabulaeformis)is a typical ECM plant,which may have considered one of the main afforestation species on the Loess Plateau and plays an important role in vegetation reconstruction and ecological civilization construction.The majority of Pinus tabulaeformis plantations in this region entering the middle age and mature trees forest stage,the problem of difficult natural regeneration,that has been gradually become a prominent,and become a vital problem that need to be solved in the sustainable management of Pinus tabulaeformis plantations in this area.In this present work,that healthy Pine forests(plantation forests and natural secondary forests)of different origins were selected in the Huanglong mountain forest area of Shaanxi Province of China,and the natural regeneration and regeneration status of different origin forests were studied.The roots of mature trees and seedlings were collected separately.Based on the observation of anatomical and morphological characteristics,and the classification of ECM types,the technique like DNA detection technology was also used to identify the symbiotic fungi,and the comparison between the plantation forest and the natural forest ECM were investigated.The differences in diversity,as a result the composition and diversity of ECM fungal communities in seedlings and mature trees,combined with the natural regeneration of plantation and natural forests,discovered the influences of ECM on artificial natural regeneration of Pinus tabulaeformis.Simultaneously,the top soil was collected from the ex-situ condition,and the surface soil was also collected.After autoclaved,the potted seedlings were planted and tested.In addition,the effects of soil microorganisms including ECM fungi on the growth of Pinus tabulaeformis seedlings were evaluated.The main findings of this study are given bellow:1.According to the morphological and anatomical features of ECM from different origin forest of seedlings and mature trees,they were firstly divided into 74 ECM types.A comparative analysis of ECM types of different forest types revealed that 26 types only appeared in natural forest,and 17 types only appeared in plantation forest;analysis of ECM root types of different ages of Pinus tabulaeformis species that found only 39 types appeared in fully developed forest roots,12 types appear in the roots of seedlings.2.Approximately,74 ECM types of ITS(Internal Transcribed Spacer),sequencing was divided into 76 OTUs,which belong to 2 phylums,5 classes,11 orders,18 families,and 24 genera.Among them,the 58 ECM types of mycorrhizal fungi belong to Basidiomycota and 18 belong to Ascomycota.The ECM fungi found on the roots of mature trees can be divided into 64 OTUs,of which Cenococcum geophilum was the dominant species;the ECM fungi found in the roots of Seedlings can be divided into 34 OTUs,of which Cenococcum geophilum and Amphinema sp.were dominant species;The fully mature trees forests and 22 of the ectomycorrhizal fungi that updated the roots of the seedlings that belong to the same OTUs.3.There were significantly differences in the community composition of ectomycorrhizal fungi in different origins forest of Pinus tabulaeformis.The ectomycorrhizal fungi of natural forest divided into 59 OTUs(including,50 species of mature trees,21 species of seedlings,12 identical as well);the ectomycorrhizal fungi of plantation divided into 50 species(including,41 mature trees,19 species of seedlings and 10 identical).Among them,27 species were observed in all mature tree roots,6 species were found on all seedlings,and 4 species were revealed in all roots of Pinus tabulaeformis.Non-metric multidimensional scale(NMDS)and permutation multivariate analysis of variance(PERMANOVA)a significantly difference was noticed in ECM fungal community composition of different origins.4.There was also a significant difference in the diversity of ectomycorrhizal fungi in dissimilar origins forest of Pinus tabulaeformis was observed.The richness index in plantation forest was found lower as compared to natural forest.The Shannon index,Simpson index and Pielou index of diversity were found to be higher in plantation forest rather than natural forest.On the other hand,the difference was varying in the seedlings,among them,the difference between the richness index and the Shannon index was not significant.5.Natural forest and plantation forest revealed a significantly differences in the regeneration of natural seedlings.Among them,the density of 1-5 years old regeneration seedlings in natural forests was 3332 plants/hm2,and that of plantation forests was 932plants/hm2.Meanwhile,the obtained results of ECM community composition and diversity were analysis.The differences in composition and diversity of ECM communities in forest soil of Pinus tabulaeformis showed that the natural regeneration of Pinus tabulaeformis was different in the different origin forest that was the main reasons for natural regeneration seedlings of natural forests and superior to that of plantations.6.Soil microbes have a significant impact on the growth and development of Pinus tabulaeformis.Soil microbes(including ECM)encouraged the growth and development of Pinus tabulaeformis seedlings and the accumulation of phosphorus in the plant.Such as increased seedlings base diameter,leaf length,biomass,and phosphorus content.In contrast,the sterilized soil substrate,although the Pinus tabulaeformis seedlings can grow normally,the growth rate was lower than that of the non-sterilized soil(control);the seedlings cultivated by the non-sterile soil substrate have higher SOD,POD,ROS activity and lower MDA activity.In summary,the ECM bacteria in the soil of Pinus tabulaeformis forests in Huanglong forest area are rich in resources.The Pinus tabulaeformis forests with different origins have significant differences in the composition and diversity of soil ECM fungal.There are important reasons for the potential difference in natural regeneration seedlings between plantation and natural forest.Overall,ECM plays an important role in the colonization and growth of natural regeneration seedlings and sustainable development of Pinus tabulaeformis in the Loess Plateau. |
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