| Straw returning and crop rotation are widely used in farmland ecosystem management,but the effect of straw returning and crop rotation on the soil fauna community diversity in the purple soil area is still unclear.Five experimental treatments for straw returning and rotation were selected to evaluate the effects of different straw returning amount and different rotation methods on the soil fauna community in Yanting agro-ecological station of purple soil,Chinese Academy of Sciences.The four straw returning treatments including 100%(RMW1),50%(RMW2),30%(RMW3)and 0%(CK)of straw returned and the two crop rotation methods of maize-wheat(RMW2)and maize-rape(RMR)were conducted.each treatment has four repeated plots.The soil microarthropod communities,nematode communities and environmental factors in the RMW1,RMW2,RMW3,CK and RMR were monitored in September,2011 and September,2018.The main results were the followings:With the increase of straw returning,the contents of soil organic matter,total nitrogen,available nitrogen and available potassium increased significantly(P<0.01 or 0.001).Different rotation methods only had significant effects on available phosphorus,and soil available phosphorus in the maize-rape rotation was significantly higher than in the maize-wheat rotation(P= 0.001).The results showed that the effect of different straw returning amount on soil chemical properties was more extensive than that of different rotation patterns.The prolongation of the years of straw returning and rotation could significantly increase the total phosphorus,available nitrogen,available phosphorus and p H(P<0.05 or 0.001).The results indicated that the years of straw returning and rotation could significantly affect soil chemical properties.There were significant differences in soil arthropod community composition and diversity among the four straw returns.With the increase of straw returning,the community density and Shannon index both first increased and then decreased,and were the largest at 50% of straw returning;the Simpson index showed a fluctuating downward trend,and the 100% of straw returning was the minimum;the Richness continued to increase,and Pielou index presented the upward trend of fluctuation,both of them were maximal at 100% of straw returning.Compared with the control group,straw returning significantly increased the density(30% and 100% of straw returning enhanced but not remarkable),Richness,Shannon index and Pielou index(50% of straw returning enhanced but not remarkable)(P<0.01 or 0.001),and obviously reduced the Simpson index(P<0.01).The prolonged straw return years significantly increased the Richness,Shannon index,Pielou index(P<0.05 or 0.01),and significantly reduced Simpson index(P<0.05).It was showed that the density and diversity of soil arthropod community could be improved by increasing the amount and years of straw returning.The effects of environmental factors on soil arthropod community density and diversity under different treatments were also different.The density of soil arthropods was significantly positively correlated with total potassium and available potassium(P<0.05),and soil arthropod diversity was significantly positively correlated with soil Organic matter,available nitrogen and available potassium(P<0.05 or 0.01).There were some differences in soil arthropod community composition between the two kinds of rotation modes,whereas had no significant effect on the density,Richness,Shannon index,Simpson index and Pielou index(P>0.05).The increase of the rotation years significantly increased the density,Richness,Shannon index and Pielou index(P<0.05 or 0.01),while the Simpson index was on the contrary(P<0.05).The effects of environmental factors on soil arthropod community density and diversity between two kinds of rotation methods were also different.The density was negatively correlated with organic matter(P<0.01),and the richness was positively correlated with total nitrogen and p H(P<0.05 or 0.01).Our results suggested that rotation management changed the soil arthropod community through the changes of the rotation years,soil organic matter,total nitrogen and p H.There was some effect on soil nematodes community composition among the four straw returns,and the density,Richness,Shannon index,Simpson index and Pielou index were not significantly impacted by different straw returning amounts(P>0.05).The prolonged straw return years significantly increased the density,Richness,Shannon index(P<0.05 or 0.01),and significantly reduced Simpson index(P<0.05).With the increase of straw returning,the abundance of fungal nematodes was decreasing first and then increasing;the abundance trends of predatory-omnivorous nematodes increased first and then decreased,and was maximal at 50% of straw returning;compared with the CK group,straw returning significantly reduced the abundance of fungal nematodes(excluding 100% of straw returning)(P<0.001)and obviously increased the abundance of predatory-omnivorous nematodes(P=0.001).With the increase of straw returning,the basic index was decreasing first and then increasing;the maturity index increased first and then decreased,and was maximal at 50% of straw returning;compared with the control group,straw returning significantly decreased the basic index(excluding 100% of straw returning)(P=0.001)and obviously enhanced the maturity index(P<0.001).The nutrient structure and ecological index of soil nematode community were affected by various environmental factors.This study shows that the soil food network of the purple soil area was a decomposition pathway dominated by bacterial decomposition,but the proportion of fungal decomposition increased with the increase of straw return.Straw returning enhanced the maturity and stability of soil ecosystem.Different rotation methods had a weakly effect on the community composition,nutrient structure and ecological index of soil nematode(P>0.05).Predatory-omnivorous nematodes was the common dominant nutritional group of the two rotation methods.The two rotation methods had little effect on the density,Shannon index,Simpson index and Pielou index(P>0.05),and only had significant effect on the Richness(P<0.05).The maize-rape rotation sharply increased the number of soil nematode groups.The increase of the years of rotation significantly increased density,Shannon index and Richness of soil nematode community(P<0.05 or 0.01),and sharply decreased the Simpson index(P<0.05).The results showed that different rotation methods had little effect on soil nematode communities,but the extension of rotation years was beneficial to soil nematode community.The abundance of bacterial-feeding nematodes was much higher than that of fungal nematode under the two rotation modes,indicated that both rotation modes were beneficial to the fungal nematode.The channel index of both rotation methods were less than 50,it showed that the two rotation methods were mainly based on bacterial decomposition.The research results show that the response of soil fauna community in farmland to different straw returning amounts is stronger than that of different rotation methods,and both the years of straw mulching and crop rotation have significant influence on soil fauna community.When the level of 50–100% of straw returning were optimal in purple soil area in terms of maximizing arthropod diversity,and 50% is also conducive to maintain the diversity of nematode community.The increase of straw returning can change the structure and function of nematode food network,thus affecting the material circulation and energy utilization efficiency of farmland ecosystem and enhance the stability of soil ecosystem.We suggest that more than 50% crop straw should be returned to the farmland in purple soil area for a long time,which is conducive to maintaining higher soil biodiversity and exerting normal ecological function. |
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