Responses Of Soil Microbial Communities To Typical Artificial Plantations With Different Ages In A Loess Area

Phospholipid fatty acids(PLFAs)can be used as biomarkers for qualitative and quantitative analyses of soil microbial community diversity.In this study,we collected soil samples at 10-cm intervals to a depth of 1 m from Robinia pseudoacacia,Caragana korshinskii and Medicago sativa plantations with different ages(R.pseudoacaciaof 10,15,25 and 40 years;C.korshinskiiof 38,42 years;M.sativaof1,10,20 and 30 years)in a loess area and analysed the soil microbial community structure by PLFA analysis.1)The results showed that 97 PLFAs,92 PLFAs and 91 PLFAs were detected in soils of R.pseudoacacia,C.korshinskii and M.sativa plantations with different ages.The content of the individual PLFAs were mainly concentrated on the surface of the soil,with little variation in the 40-100-cm soil layers.The contents of individual PLFAs showed a similar distribution patterns in the soils of typical artificialplantations.The 16:0 content was the highest among individual PLFAs.2)The total PLFA content and the PLFA contents of different microbial groups [bacteria,fungi,Gram-positive bacteria(G+),Gram-negative bacteria(G-)and actinomycetes] obviously affected by the ages of vegetation and the depth of the soil.The PLFA contents of different microbial groups ranked as follows: bacteria > G-> G+> actinomycetes >fungi.3)The principle component analysis showed that,in the soil of R.pseudoacacia,18:1?9c,10Me18:0,i17:0,a17:0,18:1?7c,18:1?5c and 18:0 made the greatest contribution to principal component 1,and a14:0,i14:0 3OH,i14:0,i14:1?7c and 14:0 made the greatest contribution to principal component 2;In the soil of C.korshinskii,10Me16:0,i17:0,cy17:0?7c,i15:0,a15:0,i16:0,16:1?7c,a17:0,18:1?5c and cy19:0?7c made the greatest contribution to principal component 1,and18:2?6c and 18:1?9c made the greatest contribution to principal component 2.In the soil of M.sativa,10Me17:1?7c and i22:0 about 22 varieties of PLFAs made the greatest contribution to principal component 1,and21:1?3c made the greatest contribution to principal component 2.In conclusion,soil nutrient status and other soil eco-environmental stress factors should be considered in different years(particularly the 25-year-oldR.pseudoacacia,the 42-year-old C.korshinskii,the 10-year-old M.sativa)plots for the management of typical artificial plantations to prevent forest soil degradation and improve forest stand quality,thereby better achieving soil and water conservation and environmental improvement inartificialplantations.