Effect of different land use types on soil aggregates microbial biomass and community composition in the loess hilly region of west Henan

Microbial biomass and community composition in aggregates of different land use types in the loess hill region of west Henan were analyzed by fumigation extraction method and phospholipids fatty acids (PLFA) biomarkers. Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents were the highest in aggregate of 0.25~2.00 mm and lowest in 0.053~0.250 mm. Compared with the farmland, the MBC and MBN contents in >5 mm, 2~5 mm and 0.25~2.00 mm aggregates of broad-leaved mixed forestland, Robinia pseudoacacia plantation forestland and shrub-grass land were significantly increased(P<0.05), which in orchard and farmland were no significant difference(P>0.05). The PLFA contents of bacteria were the highest in the 0.25~2.00 mm aggregates, however, the highest proportion of bacteria to total PLFA were found in 0.053~0.250 mm aggregates in all different land use types. The PLFA contents of fungi and its proportion to total PLFA in the >5 mm aggregates were the highest and induced with the decrease of the aggregates size. The contents of MBC and MBN present a notable positive correlation with the PLFA contents of the bacteria and fungi(P<0.05 or P<0.01). Compared with the farmland and orchard soil, the contents of fungi in>5 mm, 2~5 mm and 0.25~2.00 mm aggregates of broad-leaved mixed forestland, R. pseudoacacia plantation forestland and shrub-grass land increased significantly. To sum up, soil microbial biomass and fungi PLFA contents in >0.25 mm aggregates of broad-leaved mixed forestland, R. pseudoacacia plantation forestland and shrub-grass land were significantly increased compared with farmland and orchard.