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Soil fauna regulate soil processes affecting soil organic matter decomposition,mineralization and nutrient cycling,and play an important role in terrestrial ecosystem nutrient cycling and energy flow.Management of cropland,especially long-term fertilization,has considerable impacts on soil properties,and also affects the composition of soil faunal communities.The Sichuan Basin is an important agribusiness area in southwestern China which occupies 7% of the national cropland and supplies 10% of the agricultural products of China.The typical soil in the study area is highly productive and is called "purple soil" locally.It is classified as a Pup-Orthic Entisol in the Chinese Soil Taxonomy and an Entisol in the U.S.Taxonomy.However,the influence of long-term fertilization regimes on soil faunal communities and how indices of these soil faunal communities respond to changes in soil properties are poorly understood.To investigate the effects of long-term fertilization regimes on the soil faunal communities and their inter-relationships,seven fertilization regimes,a control with no fertilization(Control Check,CK),nitrogen fertilizer only(Nitrogen,N),a mixed synthetic fertilizer(Nitrogen Phosphorus Potassium,NPK),organic manure(Organic Manure,OM),organic manure plus synthetic fertilizer(Organic Manure Nitrogen Phosphorus Potassium,OMNPK),crop residues returned to the soil as fertilizer(Returning Straw Decomposition,RSD) and crop residues plus synthetic fertilizer(Returning Straw Decomposition Nitrogen Phosphorus Potassium,RSDNPK) were applied to the purple soil of the Sichuan Basin,China,and examined in May,July,September and November,2008 using modified Tullgren and Baermann funnels.A total of 9,454 individuals were collected,and classified into seven phyla,17 classes and 24 orders.Analysis of the data showed that the soil faunal communities were richer in the OM,OMNPK and RSDNPK plots,and that the greatest diversity of the soil faunal communities was found in the OM and RSDNPK plots,being significantly higher than those in the CK,N and NPK plots.Application of organic fertilizers promoted diversity and abundance of soil faunal communities,and was favorable for their survival and development.Analysis of variance indicated that different fertilization regimes had extremely significant impacts on the density of the main soil faunal groups(F=42.412,P=0.0001) and led to imbalances being present in the soil faunal groups.Analysis of the relationships between the fertilization regimes and the main groups of the soil faunal communities,using Principal Component Analysis,showed that the different fertilization regimes primarily affected six indices of soil fauna;individuals in the soil faunal population,individual nematodes,individual megadriles,individual Oribatidas,the DG index(density-group diversity index) and total groups in the soil faunal communities.Therefore,we consider that changes in the cropland soil faunal communities have a relationship with differences in long-term fertilization management.These six indices of the individual soil fauna population;individual Nematodes,individual Megadriles,individual Oribatidas,the DG index(density-group diversity index) and total groups in the soil faunal communities can be used to predict changes of soil fertility caused by long-term fertilization application,and have great potential as bio-indicators of changes in soil quality.