| The phenomenon of forest erosion and degradation occurs widely in the red soil regions of Southern China.Pinus massoniana is the pioneer tree species in the ecological restoration and reconstruction of the red soil erosion areas in Southern China.However,due to the single vegetation structure of the Pinus massoniana plantation,the lack of understory vegetation,and the concentrated rainfall during the rainy season,the ecological environment of plantation area is easily degraded under the long-term serious erosion.At present,the restoration of degraded plantation areas has received more attention,and the construction of diversified and threedimensional vegetation system is very important for the restoration of forest ecosystem.The existing studies mostly focus on the effects of multiple treatment patterns on reducing runoff and sediment and improving soil fertility,while less attention is paid to the changes of soil microorganisms under different treatment approaches.In order to reveal the response of soil microorganisms to the different combinations of vegetation construction patterns,this study took the eroded soil in the Pinus massoniana planation area as the research object,and set up four combinations of vegetation construction patterns(digging fish scale pits and planting Lolium perenne L.,digging fish scale pits and planting Lolium perenne L.and Lespedeza bicolor Turcz.,digging horizontal furrows and planting Lolium perenne L.,digging horizontal furrows and planting Lolium perenne L.and Lespedeza bicolor Turcz.)and a control group without any measures.High-throughput sequencing molecular technology are used to analyze soil microbial diversity and community structure.Further,the molecular ecological network analysis method are used to compare the changes of the soil microbial interaction network and the interaction relationship under different treatments.Based on these,the relationships between soil microbial characteristics and soil physicochemical factors were studied.Finally,we used principal component analysis method to analyze the soil quality improvement benefits under different vegetation construction patterns from the aspects of soil physicochemical properties and microbial properties.Suggestions on ecological restoration of eroded and degraded forest areas were put forward.This research mainly draws the following research conclusions:(1)Vegetation construction patterns had a great influence on some soil basic physicochemical properties.The soil water content and soil C/N ratios with patterns of fish scale pit with grasses and shrubs,horizontal furrow with grasses,and horizontal furrow with grasses and shrubs,were significantly higher than that in the control group.Soil organic matter content under the four vegetation construction patterns were significantly increased comparing with that of the control group.(2)Vegetation construction patterns had a great influence on some soil microbial properties.The Chloroflexi is the highest relative abundance of bacterial phylum,and it had been found at a significantly lower rate in the soil bacteria under the horizontal furrow with planting grasses measure and the horizontal furrow with planting grasses and shrub measure compare to the control group.The Ascomycota is the highest relative abundance of fungal phylum and the abundance of Ascomycota does not show significant difference between the soil with vegetation construction patterns and the control group.Under soil with the vegetation construction patterns,the scale of the soil microbial molecular ecological network is enlarged,the structure is more complex,and the competition between microbial species is strengthened.(3)Soil bacterial alpha diversity is closely related to organic matter content,total nitrogen content,and soil carbon and nitrogen in the Pinus massoniana forest area,while soil fungal alpha diversity is closely related to soil water content,p H,soil organic matter content,and soil carbon to nitrogen ratio.The explanatory degree of soil physical and chemical properties to the change of soil bacterial community structure in Pinus massoniana plantation was 85.00%,which was higher than that to the change of fungus community structure(40.95%).Soil water content and p H have a significant impact on the variation of bacterial communities.Soil bulk density and soil water content have a significant impact on the variation of fungal community structure.In addition,the structure of soil microbial molecular ecological network was significantly affected by soil carbon and nitrogen nutrients,and the complexity and stability of the network structure is positively correlated with the content of soil carbon and nitrogen nutrients.(4)Soil quality under the vegetation construction patterns was improved in different degrees.Three principal component factors were obtained through component analysis,which explained 80.075%,12.019%,and 7.468% of the total variance variation respectively.The obtained soil quality under different treatments is ranked as follows: horizontal furrows with planting Lolium perenne L.and Lespedeza bicolor Turcz.> fish scale pits with planting Lolium perenne L.and Lespedeza bicolor Turcz.> horizontal furrows with planting Lolium perenne L.>fish scale pits with planting Lolium perenne L.> control group.Compared with the control group,the four combinations of soil erosion control measures improved the soil in the Pinus massoniana forest area.In summary,the vegetation construction patterns in the Pinus massoniana plantation area had changed the characteristics of soil microbes,effectively improved the diversity of soil microbes,changed the soil microbial community structure and soil microbial interaction network,and improved the stability of the microbial community.The vegetation construction patterns of each combination improved the soil quality to some extent.Among these vegetation construction patterns,the pattern of horizontal furrows with planting Lolium perenne L.and Lespedeza bicolor Turcz.had the most prominent effect. |
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