| In order to understand the spatial pattern of Ectomycorrhizal fungi community in a mixed forest of Pinus massoniana-Castanopsis eyrei in subtropical mountain,a sample plot of natural secondary P.massoniana-C.eyrei mixed forest and a pure artificial P.massoniana forest(control)in Kaiyang County,Guiyang was selected to investigate the composition and diversity of ectomycorrhizal fungi community in two planting types.The spatial distribution pattern of ectomycorrhizal fungi at community level was analyzed based on geostatistics.Correlation analysis,redundancy analysis(RDA)and,ecological network were used to analyze the factors affecting the spatial distribution pattern of ectomycorrhizal fungi communities.The main research results are as follows:(1)The results of plant community investigation showed that 38 vascular plant species were recorded in the P.massoniana-C.eyrei mixed forest and 34 vascular plant species in the P.massoniana pure forest,belonging to 25 families,34 genera and 22 families,31 genera,respectively.The diversity index and evenness index of the plant community were shrub layer>herb layer>Arboreal layer,and the evenness index of each life type was greater than 1.The richness index,diversity index and evenness index of the tree layer and shrub layer were higher than those of the pure P.massoniana forest.Except for soil available P and available K,the coefficient of variation of other soil nutrient indexes showed that the mixed forest of P.massonianaC.eyrei mixed forest was higher than that of the pure forest of P.massoniana,showing moderate variation(except pH).The spatial heterogeneity of soil nutrient indexes in P.massoniana-C.eyrei mixed forest was higher than that in P.massoniana pure forest,and the overall spatial autocorrelation was stronger at a small scale(except pH).The spatial distribution of soil nutrient indexes in P.massoniana-C.eyrei mixed forest was more obvious than that in P.massoniana forest(except TP).Crossover verification results showed that soil nutrient survey of P.massoniana-C.eyrei mixed forest needed larger sample volume.The results of this study showed that the soil sampling area should be determined in combination with the complexity of microhabitats and specific investigation indicators,as the contents of each index of forest soil nutrients were affected by different habitats.(2)A total of 90 ectomycorrhizal fungi OTUs were identified in the P.massoniana-C.eyrei mixed forest,belonging to 2 phyla,6 classes,13 orders,20 families and 20 genera.A total of 66 ectomycorrhizal fungi OTUs,belonging to 2 phyla,6 classes,12 orders,15 families and 16 genera,were identified in P.massoniana pure forest.The diversity index,Simpson dominance index and Shannon diversity index of ectomycorrhizal fungi community in the mixed forest of P.massoniana-C.eyrei mixed forest were significantly higher than those in the pure forest of P.massoniana,while the evenness index of Pielou was lower than that in the pure forest.These results indicated that the diversity of ectomycorrhizal fungi in the mixed forest was higher than that in the pure forest,but the homogeneity was lower.The similarity of ectomycorrhizal fungi in the two plots was low,and the Jaccard similarity index was only 0.23,indicating that the mixed forest with P.massoniana-C.eyrei mixed forest greatly changed the species composition of ectomycorrhizal fungi community compared with the pure forest of P.massoniana.The dominant genera in the P.massoniana-C.eyrei mixed forest and P.massoniana pure forest were Lactarius,Hyphodiscus,Tomentella and Russula,Sebacina.Different trees in mixed P.massoniana-C.eyrei mixed forest ectomycorrhizal fungi community diversity index,Simpson dominance index,Shannon diversity index were characterized by: C.eyrei>P.massoniana>Quercus acutissima,Pielou evenness index was characterized by: Quercus acutissima>P.massoniana>C.eyrei.The Jaccard similarity index among different host Ectomycorrhizal fungi communities was only 0.081～0.027,indicating that the symbiosis between different host plants and ectomycorrhizal fungi had high specificity.(3)The Ectomycorrhizal fungi community in the mixed forest of P.massoniana-C.eyrei and pure P.massoniana forest showed a high degree of structure and strong modularity,and the Ectomycorrhizal fungi of the same genus tended to be the same module and had a scale dependence.The spatial distribution of the Ectomycorrhizal fungi community in the mixed forest of P.massoniana-C.eyrei showed obvious characteristics of clustered patches.The species of ectomycorrhizal fungi varied significantly among different sampling units,and the patch sizes of high and low abundance of all Ectomycorrhizal fungi and rare Ectomycorrhizal fungi were different.On the other hand,Ectomycorrhizal fungi in the pure P.massoniana forest showed a large area of flaky distribution,which was consistent with the spatial distribution of soil nutrients.The results showed that the spatial distribution pattern of Ectomycorrhizal fungi in the mixed forest with P.massoniana-C.eyrei and pure forest P.massoniana was significantly affected by the differences of soil and host plants.(4)The study on the single root tip "composite mycorrhizal" of P.massoniana pure forest and P.massoniana-C.eyrei mixed forest in subtropical mountain showed that the symbionts of single root tip composite mycorrhizal fungi were all composed of two fungal combinations,and the 13 single root tip "complex mycorrhizal" fungi were mostly composed of two Ectomycorrhizal fungi(accounting for 61.5%of the total number of complex mycorrhizal fungi).This indicated that there was a wide range of competition or growth promoting relationships among ectomycorrhizal fungi.In addition,"complex mycorrhiza" accounted for about 5% of the total mycorrhiza root tip samples,which was lower than that reported in previous studies on "composite mycorrhizal".(5)Taking site conditions,plant communities and soil properties as environmental factors,the driving factors of spatial distribution pattern of Ectomycorrhizal fungi were analyzed.The results showed that Hyphodiscus was positively correlated with shrub coverage in the mixed forest with P.massoniana-C.eyrei.Archaeorhizomyces were significantly positively correlated with herb coverage.Oidiodendron was significantly negatively correlated with herb cover,herb layer species richness,and arbor layer species richness.In the pure P.massoniana forest,the species richness of Tomentella was positively correlated with that of shrub layer.Lactarius and Hyphodiscus were negatively correlated with the coverage of herbaceous species.Penicillium was negatively correlated with total species richness,shrub layer species richness and herb layer species richness.The results of correlation network showed that different fungal groups were affected by different environmental factors in both P.massoniana-C.eyrei mixed forest and P.massoniana pure forest,and the abundance of trees had the greatest effect on exogenous mycorrhizal fungi.RDA analysis showed that available K,pH and available P were important environmental factors affecting Ectomycorrhizal fungi community in P.massoniana-C.eyrei mixed forest.Available potassium,pH and nitrogen are important environmental factors affecting the mycorrhizal fungi community outside P.massoniana pure forest. |
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