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Three croplands,which all are 5 meters long,at 5°,15° and 25°slope gradients respectively,were selected in the hilly areas of Central Sichuan Basin in March and September 2010.The investigations were conducted to study the effects of slope gradient on soil fauna.The methods of Tullgren and Baermann were used to extract soil fauna from soil samples(0—15cm).A total of 11 657 individuals,belonging to 3 Phylum,11 Classes,and 21 Orders,were extracted from the soil.The orders of Springtails,Mites,Tubificida and Nematode were the dominant groups of the soil fauna community in Hilly areas of Central Sichuan Basin.As slope increased,the taxonomic richness of soil fauna was not significantly changed in March(P0.05),but increased significantly in September(P0.01).The community density decreased significantly with the increasing of slope gradient in Mach(P0.01),but increased in September(P0.05).Diversity indexes fluctuated with slope gradient in March,as well as in September.The abundance of the major taxonomic groups varied in their response to slope increasing.The result of a principal component analysis(PCA) indicated that the community structures of soil fauna differed obviously among three slope gradients.Furthermore,the coefficients of Sorenson and Morisita-Horn suggested that effects of the slope on the taxonomic composition of soil fauna communities were stronger than on the abundance of the dominant groups in March,while the opposite was found in September.The results of ANOVA and t-test indicated that both slope and season had a significant effect on the diversities of soil fauna community and the abundance of the major taxa.However,the effects of slope on the diversity also varied with seasons.The results of our research suggested that the slope has a significant effect on the structure and diversity of soil fauna community and the abundance of major groups,which were also changed with the seasons.Further analysis showed that the soil water was the main reason for the differences among the community abundance and the soil erosion for the diversities of soil fauna.

Abies faxoniana forests create a zone of vegetation in the northwestern Sichuan alpine valley area and are important ecologically and as a center of biodiversity.This zone is sensitive to global climate change and is located in the eastern portion of the Qinghai-Tibet Plateau and the upper reaches of Yangtze River.After long-term extensive logging on a broad scale,the extent of these forests has been greatly reduced and the forests themselves degraded.More recently,forest restoration and regeneration are being emphasized in the region including old growth natural forests,plantation forests and natural secondary forests.Wolong Nature Reserve and Miyaluo Forest District were selected as an area to study soil faunal dynamics during the restoration of A.faxoniana forests.The study was conducted in old-growth A.faxoniana forest(OAFF) and 50-year-old A.faxoniana forest(50AFF) in April 2008.This study was conducted in northwestern Sichuan Province(27°57′—34°21′N,97°26′—104°27′E),China.A total of 287 soil macrofauna individuals and 4681 soil meso-microfauna individuals,belonging to 33 and 57 families,respectively,were collected during the study.Three dominant groups,the Doratodesmidae,Paradoxosomatidae and Curculionidae,accounted for 62.02% of the soil macrofauna individuals.Nematoda dominated the soil meso-microfauna,accounting for 81.01% of the individuals.The number of taxonomic groups and the individual density of soil macrofauna in the 50AFF were significantly higher than those of the OAFF(P0.05).The number of taxonomic groups of soil meso-microfauna in the 50AFF were significantly lower and the individual density was significantly higher than those of the OAFF(P0.05).PCA ordination suggests the community structures of the two soil macrofauna communities were more different than those of the soil meso-microfauna communities.The similarities between the two soil macrofauna communities were lower than those of soil meso-microfauna,and the values of the Srenson Index were lower than those of the Morisita-Horn Index.This implies the recovery rate is slower for the soil macrofauna than the soil meso-microfauna,and the restorative process has a relatively stronger influence on the taxonomic compositions of the soil macrofauna community than on the individual densities of the dominant and common taxonomic groups.Several ecological indices,such as species richness,abundance,and a diversity index,were analyzed.The Shannon(H),Margalef(D) and Simpson(C) indices of soil meso-microfauna communities in 50AFF were higher and the Pielou Index(E) was lower than that of the OAFF.But a significant difference(P0.05) between the two soil macrofauna communities was only recorded with the Margalef Index(D).Correlation analysis suggests the group number and mean density of the soil macrofauna were remarkably positively correlated with organic matter content(P0.05);the group number was remarkably positively correlated with litter depth content,but was also markedly negatively correlation with total N content(P0.05).The group number and mean density of the soil meso-microfauna were only positively correlated with soil bulk density content(P0.05).All results above showed the restoration of A.faxoniana forests can significantly improve soil macrofauna diversity;the taxonomic composition of the soil fauna community recovered slowly,but the individuals of the dominant and common taxonomic groups recovered rapidly.