Effect Of Quantity Of Returned Corn Straw On The Cropland Soil Fauna Community In A Black Soil Area

In order to understand the effect of quantity of returned corn straw on the croplandsoil fauna community in a black soil area,an experiment with six different amounts of corn straw returned to the field 0(CK),9000(SRI),10500(SR2),12000(SR3),13500(SR4)and 15000(SR5)kg·hm-2 was carried out in Zhalaid Banner of Inner Mongolia from June to September 2016-2018.The community characteristics of soil mesofauna,ground arthropod and macrofauna were investigated by Tullgren method,pitfall trap method and hand-sorting method respectively.The soil fauna community composition,main groups,community diversity,vertical distribution,monthly dynamics,functional group characteristics and the correlation between soil fauna and soil environmental factors were analyzed.The results show that:A total of 14591 soil mesofauna were captured in the study area,belonging to 70 groups belonging to 3 classes and 10 orders of Arthropoda,and the number of dominant groups accounted for 76.22%of the total individuals.A total of 3176 ground arthropods were captured,belonging to 4 classes,8 orders and 19 groups of arthropods respectively,and the number of dominant groups accounted for 83.88%of the total individuals.A total of 2681 soil macrofauna were captured,belonging to 41 groups of 13 orders of 5 classes and 13 orders of Arthropoda and Annelta respectively,and the number of dominant groups accounted for 74.93%of the total.The soil fauna groups which are greatly affected by farmland soil environmental factors are the dominant groups in the study area and constitute the main body of the soil fauna community in the study area.The different amount of corn straw returning to the field affected the composition of soil fauna community in farmland.SR2-SR5 treatment significantly increased the individuals of soil mesofauna(P<0.05),SR4 and SR5 treatment significantly increased the number of ground arthropod fauna individuals(P<0.05),and SR4 treatment significantly increased the individuals of soil macrofauna(P<0.05).SR1-SR5 treatment increased the group number of soil mesofauna,but only SR5 significantly increased the group number of soil mesofauna(P<0.05),and SRI-SR5 treatment increased the number of ground arthropod fauna.However,there was no significant difference(P>0.05),but SR3 treatment significantly increased the group number of macrofauna(P<0.05).And the individuals and group number of soil mesofauna,ground arthropod fauna and soil macrofauna increased with the increase of corn straw return.The diversity of soil mesofauna communities:SR5 treatment significantly increased diversity index,SR5 treatment increased richness index,but there was no significant difference(P>0.05),SR2-SR5 decreased dominance index(P>0.05),and decreased dominance index(P>0.05).SR3 and SR4 increased evenness index,while SRI and SR2 decreased evenness index(P>0.05).Ground arthropod fauna community diversity:SR1-SR5 treatment increased diversity index and richness index,there was no significant difference(P>0,05).The evenness index and dominance index were decreased by SRI-SR5 treatment,and there was no significant difference(P>0.05).Diversity of soil macrofauna community:SR1-SR5 treatment increased diversity index and richness index,and there was no significant difference(P>0.05).The evenness index and dominance index were decreased by SR1-SR5 treatment,and there was no significant difference between the two groups(P>0.05).Vertical distribution:after returning corn straw,the number of soil mesofauna in soil layer 0-10 cm was significantly higher than that in soil layers of 10-20 cm and 20-30 cm(P<0.0S)and the number of soil mesofauna communities had obvious superaggregation characteristics(P<0.05).The surface clustering property of individual number is greater than that of cluster number;The individuals and group number of macrofauna in 0-10 cm and 10-20 cm soil layers were significantly higher than those in 20-30 cm soil layer(P<0.05),and the vertical distribution of macrofauna community along with the growth stage of maize was significantly higher than that of 20-30 cm soil layer(P<0.05).The proportion of soil macrofauna in the surface layer of 0-10 cm soil layer moved downwards to that of 10-20-cm soil layer.Functional groups:corn straw returned to the field increased the number of individuals in the soil ground arthropod community,but there was no significant difference(P>0.05).The number of predatory,phytophagous and saprophytic individuals in soil macrofauna communities was increased and the number of omnivorous individuals was decreased(P>0.05),while SR5 significantly increased the individuals of predatory and saprophytic soil macrofauna(P<0.05).Principal component analysis(PCA)showed that soil mesofauna Parasitidae,Pygmephoridae and Isotomidae Borner were most sensitive to the amount of straw returned.Principal component analysis(PCA)showed that ground arthropod Grylloidea,Carabidae and Elateridae were most sensitive to the amount of straw returned.Principal component analysis(PCA)showed that soil macrofauna Lumbricidae,Carabidae and Enchytraeidae were most sensitive to the amount of straw returned.A total of 9 soil fauna community indexes were sensitive to the amount of corn straw returning to the field,and could therefore be considered as evaluation indexes to judge the nutrient status after straw is returned in a black soil area in the future.