Characteristics Of Micro-aggregate Cements In Red Soil In Different Subtropical Forest Vegetation Restoration Types

Subtropical red soil is one of the regions with the most serious erosion degradation in China.Vegetation restoration and reconstruction is an important measure to restore the ecosystem of the red soil region.Soil aggregate is the important material base,the formation and change in improving soil fertility,soil quality improvement plays an important role,the analysis of the southern red soil region of different types of vegetation restoration of soil aggregate characteristics,to improve the subtropical forest soil structure stability and ecological restoration in the red soil region to give scientific basis and guidance for the further scientific research to select different vegetation types to improve the ecological environment has very important theory value and practice significance.This study based on jiangxi province ganzhou city shicheng river source national nature reserve,select site conditions similar to those of protected area environment(fir)Remnant forest(CK:no tree species for CK),1(fir)Remnant forest transformation model(MS1:replanting schima superba,liquidambar,blueberry tree,lespedeza),(fir)Remnant forest transformation mode 2(MS2:Replanting schima superba,liquidambar,blueberry tree),mixed needle leaf and(R)(pinus massoniana-liquidambar mixed forest)and secondary broad-leaved forest(N),a total of 5 types of vegetation restoration as the research object,the five vegetation recovery type are respectively isolated from three grade(50-200?m,20-50?m,<20?m)of soil microbial communities of organic carbon,iron,aluminum oxide,combined with state(calcium,iron,aluminum keys combined organic carbon)and index analysis,to explore different vegetation restoration type micro aggregate forest red soil microbial community structure,iron,aluminum oxide,and combined with the feature of state organic carbon content,To further understand the formation and change characteristics of soil microaggregates of different vegetation restoration types in subtropical region.The main conclusions are as follows:(1)the total content of total phospholipid fatty acids(TPLFAs)in soil microaggregates of different vegetation restoration types showed that the TPLFAs decreased gradually with the deepening of soil depth,and the TPLFAs decreased with the increase of soil grain size.In all soil layers with different vegetation restoration types,compared with CK,R can significantly improve TPLFAs of soil microaggregates at each grain level,while in N,TPLFAs of soil microaggregates at each grain level has a downward trend.In N,TPLFAs topsoil with particle size<20?m was significantly higher than other soil layers,and the topsoil gradually decreased with the increase of depth percentage.TPLFAs of<20?m in MS1 increased to a certain extent(21.54%higher than CK),and TPLFAs of<20?m in MS2 showed almost no increase or decrease,indicating that hu zhizi supplemented by MS1 could increase the total PLFAs content of less than20?m in the middle soil layer to a certain extent.(2)there were significant differences in microaggregates in different soil layers with different types of vegetation restoration.Different vegetation restoration each graded bacteria PLFA content significantly decreased with soil depth deepening,the soil arbuscular mycorrhizal fungi(AM)and fungal PLFAs content increases with graded successive significantly reduced tendency,actinomyces PLFAs content increases with the decrease of the graded gradually reducing,the soil layer is roughly 20-50?m fraction of gram positive bacteria PLFA content higher than 20-50?m and<20?m fraction.Compared with CK,the R points 50-200?m and<20?m fraction(AM)significantly higher PLFAs content,N soil and shallow each graded AM and fungal PLFAs content significantly lower,deep soil N and R<20?m fraction significantly higher fungal PLFAs content,N and R can significantly improve the soil is less than 20?m fraction actinomycetes PLFAs content,R and CK bacteria PLFA content is significantly higher than other types of vegetation restoration,MS1,MS2 and N content of bacterial PLFAs basic indifference and were significantly lower than other types of vegetation restoration.(3)there was basically no significant difference in microbial species richness(S),Shannon-Wiene index,evenness index(E_H)and Simpson index(D)among soil microbial communities of different vegetation restoration types in the same soil layer.Among them,the S index of 50-200?m and<20?m in R is significantly higher,and the S index of<20?m in MS2 is significantly lower.The N and R evenness(E_H)of the 20-50?m grain size in topsoil decreased significantly,and the<20?m grain size E in R was the lowest.Both R and N could significantly increase the H'and D indices of the 20-50?m grain size,indicating that R and N had significant effects on the community structure of the soil microbial community at the 20-50?m grain size.The D index of 50-200?m in topsoil MS1was significantly lower.(4)different types of vegetation restoration on soil aggregate iron aluminum oxide also has great influence,each graded soil with soil micro aggregate performance for iron and aluminum oxide content,content of free iron oxide(Fe_d)is much higher than that of amorphous iron oxides(Fe_o)and complexing iron oxide(Fe_p),and is least Fep,different forms of alumina,free aluminum oxide(Al_d)and the content of amorphous iron oxides(Al_o)is much higher than complexing state aluminum oxide(Al_P),namely the Fe_d>Al_d>>Fe_o>Al_o>>Fe_p>Al_P.The general trend of the activation degree of soil iron and aluminum oxides and soil iron oxide of different vegetation types was as follows:on the whole,the activation degree of iron oxide of 50-200?m was the highest,the activation degree of iron oxide of<20?m was the lowest,N>R>MS1>MS2>CK.In addition,with the increase of soil depth,fe and al oxides in the vertical sections of different vegetation restoration types showed obvious enrichment towards fine grain level.(5)the distribution rules of organic carbon content in the bond state of calcium bond and iron-aluminum bond in different vegetation restoration types all showed significant enrichment towards fine grain level.The order of organic carbon content of calcium bond in each vegetation restoration type was all R>N>MS2>MS1>CK,and the order of iron-aluminum bond organic carbon content in each vegetation restoration type was all CK>MS2>MS1>R>N.The contribution to the stability of microaggregates is obvious in the interaction between organo-inorganic complexes(Ca-SOC,Fe(Al)-SOC)and bacteria,gram-positive bacteria,fungi and actinomycetes in the deeper soil.Therefore,iron-aluminum bond organic carbon in subtropical red soil can promote the fixation of organic carbon in soil more than calcium-bond organic carbon,especially in topsoil<20?m.In conclusion,vegetation restoration is advantageous to the formation of soil,of which the most significant effect of R,N times,to a certain extent improve the soil micro aggregate TPLFAs and bacteria PLFA content,promote the soil micro aggregate iron and aluminum oxides and complexing state conversion of organic carbon,the MS1 replanting lespedeza can improve the soil<20?m TPLFAs,microorganism and organic inorganic complex and the interaction between iron and aluminum oxide is more obvious.The results can provide scientific basis and theoretical basis for the improvement of soil restoration and function in the process of vegetation restoration in subtropical forest red soil area.