| Sichuan province is the western edge of the geographical distribution of Pinus massoniana in China,the area of Pinus massoniana plantation has exceeded 900000 hm~2.In this study,Pinus massoniana was selected as the main tree species in three ecogeographic environment areas:deep hilly region(Pingchang)in the northeast of Sichuan Basin,parallel ridge valley area(Guangan)in the east and low mountain area(Yibin)in the south of the basin.In order to cultivate large diameter strategic reserve forest as the management purpose,the target tree management treatment was carried out.A fixed sample plot of 40 m×40 m was selected from the target tree management stand in each ecological distribution area,and a fixed sample plot of 40 m×40 m was selected from unmanagement stand of each ecological distribution area.From the vertical spatial relationship of forest layer,understory shrub layer and soil layer,combined with Illumina Miseq and FUNGuild function prediction,the composition,diversity,nutrition strategy and functional type of soil fungal community were studied.The purpose was to study the ecological adaptability mechanism of soil fungal community under different spatial distribution patterns in order to provide strong support for scientific guidance of Pinus massoniana plantation management.The main conclusions of this study are as follows:(1)The management of the target tree reduced the stand density,improved the growth environment of the forest,promoted the growth of the diameter of the tree.Reduced the distribution frequency of 6-8 cm diameter class plants and increased the distribution frequency of large diameter class plants above 26 cm effectively.In the three ecological distribution areas,the initial diameter order of the inverse"J"curve of the diameter distribution of the management plot moved to the higher diameter order than that of the unmanaged sample plot,and the curve showed a right skewness.The tree height distribution curves of target tree management Pinus massoniana plantation in three ecological distribution areas showed the same right low peak state,and the peak value of tree height distribution in the three ecological distribution areas was different.The target tree management effectively adjusted the mingling,uniform angle index and dominance of the stand.Pingchang and Guangan sample plots were adjusted from uniform distribution interval to random distribution interval,while Yibin sample plot was adjusted from random distribution pattern to uniform distribution pattern.(2)112 species of shrubs and herbs belonging to 54 families and 84 genera were investigated in Pinus massoniana plantation in three ecological distribution areas.Among them,79 species of shrubs belonging to 54 genera and 33 species of herbs belonging to 30genera and 21 families were investigated.A total of 5328 shrubs and herbs were investigated,including 2402 shrubs and 2926 herbs.The dominant species in shrub layer was Rubus chroosepalus(13.28%),and in herb layer were Miscanthus sinensis(30.90%),Dicranopteris dichotoma(21.38%)and Humata repens(13.44%).Pinus massoniana plantation was managed by target tree to improve the diversity and richness of herb layer,while Guangan's species diversity index(D,H)and richness index(R)were the highest.The sum of niche breadth of Eurya japonica in shrub layer and Dicranopteris dichotoma in herb layer was the largest and appeared in all treatments.The target tree management increased the niche breadth of Rubus hastifolius and Rubus chroosepalus in shrub layer and Saccharum arundinaceum,Disporum sessile and Stenoloma chusanum in herb layer.The highest niche overlap degree of shrub layer was Guangan,and the highest niche overlap degree of herbs layer was Pingchang.(3)The results of soil fungal species sequencing of Pinus massoniana plantation managed by target trees in three ecological distribution areas showed that a total of 20107fungal species OTUs were detected.Among them,Pingchang sample OTUs came from 5phyla,29 classes,89 orders,195 families,337 genera;Guangan sample OTUs came from 5phyla,30 classes,91 orders,199 families,453 genera;Yibin sample OTUs came from 5phyla,27 classes,88 orders,196 families,372 genera.Ascomycota and Basidiomycota dominated the soil in the three ecological distribution areas.The Alpha diversity of soil fungi in Pinus massoniana plantation under the target tree management in the three ecological distribution areas was the highest in Yibin,the number of species was significantly higher than that in Guangan and Pingchang,and the correlation between environmental factors and Alpha diversity was high.Beta diversity analysis showed that Yibin had the largest number of endemic species,and there were significant differences between Yibin and Guangan and Pingchang.(4)Most of the fungal pathological nutrition types in the three ecological distribution areas existed in the form of associated nutrition type,forming a high proportion of pathological nutrition type-symbiotic nutrition type combined fungal nutrition strategy.The relative abundance of symbiotic nutrient type,which obtains nutrition by exchanging resources with host cells,was the highest in Pingchang ecological area.There was no single animal pathogen in the fungal functional community,but formed group of Animal.Pathogen.Undefined.Saprotroph.At the same time,the abundance of Ectomycorrhizal.Lichenized.Wood.Saprotroph,and Ectomycorrhizal.Orchid.Mycorrhizal.Root.Associated.Biotroph in different ecological distribution areas were different. |
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