The Influence Of Land Use Patterns On Soil Bacterial And Arbuscular Mycorrhiza Fungi Community Structure In The Karst Graben Basin Of Yunnan Province,China

The karst graben basin is one of the eight types of areas for comprehensive management of rocky desertification of Yunnan province.Rocky desertification restricts the sustainable development in the karst graben basin area,and the recovery of vegetation is one of the best effective ways for treatment of rockydesertification.Soil microorganism play a key role in vegetation succession and ecological restoration process.Soil bacteria and arbuscular mycorrhiza fungi(AMF)are important soil microorganisms.Land use pattern will significantly change soil bacterial and AMF communities structures,and understand the characteristics of soil bacterial and AMF communities structural in the process of vegetation succession that it is beneficial to the control of rocky desertification in the karst graben basin.Although many studies have discussed soil microbial community structures with land use pattern changes in other karst areas,there are few studies on the effects of land use patterns coupled with soil depth on soil bacterial and AMF communities structural in the karst graben basin of Yunnan province.To reveal the structure of the soil bacterial and AMF community at different soil depths across land use changes in the karst graben basin of the Yunnan plateau,the relationship between soil bacterial and AMF communities and soil physicochemical properties were investigated for a given area containing woodland,shrubland,and grassland in Yunnan province by using next?generation sequencing technologies coupled with soil physicochemical analysis.This will provide a theoretical basis for the treatment of rocky desertification in the karst graben basin in Yunnan province.Our results show that:(1)Land use patterns can change soil physicochemical properties.In the surface layer(0-10 cm),our results indicated that the total phosphorus(TP),available potassium(AK),exchangeable magnesium(E-Mg),electrical conductivity(EC),and temperature(T)in the grassland were significantly higher than those in the woodland and shrubland,yet the total nitrogen(TN)and soil organic carbon(SOC)in the woodland were higher than those in the shrubland and grassland.In the deep layer(10-20 cm),SOC in the woodland were higher than those in the shrubland and grassland,AK and EC in the grassland were significantly higher than those in the woodland and shrubland,yet the TP,TN,pH,Moisture,and exchangeable calcium(E-Ca)in the three land use patterns were not significantly different.Moreover,the soil physicochemical properties,except for some physicochemical properties inwoodland,decreased by increasing soil depth.(2)Among the eighteen soil samples in the three land use patterns,produces 2 882 OTUs,bacteria belonged to 2 699 OTUs.The number of bacterial-OTUs in A layer and B layer were 2 373 and 2 454,respectively.Alpha indices of bacterial in the grassland were significantly higher than those in the woodland and shrubland.Alpha indices of bacterial decreased by increasing soil depth,and consistent with the change trend of soil physicochemical properties.According to the PCoA plot,there are some differences in the bacterial community structure in different land use patterns and soil depths.Proteobacteria,Verrucomicrobia,and Acidobacteria were the dominant bacteria,and their relative abundances were different in the three land use types.Proteobacteria were not significant difference in the land use patterns;Verrucomicrobia ingrassland were significantly lower than those in the woodland and shrubland;yet Acidobacteria in grassland were significantly higher than those in the woodland and shrubland.EC,E-Mg,SOC,AK,T,and TN were the most important factors affecting soil bacterial communities in the surface layer.T,AK,TN,and SOC were the most important factors affecting soil bacterial communities in the deep layer.Land use exerts strong effects on the soil bacterial community structure in the surface layer,and the effects of land use attenuation decrease with soil depth.The nutrient content of the soil surface layer was higherthan that of the deep layer,which was more suitable for the survival and reproduction of bacteria in the surface layer.(3)Among the eighteen soil samples in the three land use patterns,produces 1 442 OTUs,AMF belonged to 1 146 OTUs,3 classes,4 orders,9 families and 14 genera.The number of AMF-OTUs in surface layer and deep layer were 1 033 and 800,respectively.Soil physicochemical properties in the three land use patterns were significantly different.T,AK,EC,TN,and SOC were the most important factors affecting AMF communities in the surface layer;SOC,T,E-Mg,and Moisture were the most important factors affecting AMF communities in the deep layer.Alpha indices of AMF in the three land use patterns were significantly different.In surface layer,alpha indices of AMF in the grassland were significantly higher than those in the woodland and shrubland except Simpson index;Alpha indices of AMF in the woodland and shrubland were not significantly different.In deep layer,alpha indices of AMF in the three land use patterns were not significantly different.Alpha indices of AMF decreased by increasing soil depth,and consistent with the change trend of soil physicochemical properties.Glomeromycetes and Paraglomeromycetes were thedominant class in the three land use patterns.Glomus,Paraglomus,Claroideoglomus,Acaulospora,Ambispora,and Diversispora were the dominant genus in the surface layer.Glomus,Paraglomus,Claroideoglomus,Acaulospora,Otospora,and Diversispora were the dominant genus in the deep layer.Glomusand Paraglomuswere the dominant genus in the three land use patterns.