Effects Of Nitrogen Additions And Litter Multiplications On Soil Fauna Community Structure In The Poplar Plantations In A Coastal Area Of Eastern China

Nitrogen addition poses a threat to terrestrial ecosystems and marine ecosystems and becomes a global ecological problem.In order to study the effect of soil microenvironment and litter on soil fauna,five different treatments of nitrogen addition(0,5,10,15,30 g N·m-2·a-1)were set up in the poplar plantations.Three litter multiplications(litter removal,control,double litter)were set up under each treatment of nitrogen.The effects of nitrogen treatments and different litter multiplications on soil fauna density,group numbers,NH4+-N,NO3--N,TN,C/N,pH,SOC,MBC and the monthly dynamics of them are analyzed.The main results are as follows:(1)Nitrogen application had significant effect on soil fauna density and group numbers(P<0.05).The addition of nitrogen at the concentration of N2 and N3 had a significant promotion effect on soil fauna density and group numbers(P<0.05).There was a significant reduction in the diversity and evenness of soil fauna species under N4 treatment(P<0.05).The group numbers of herbivores,predatory and saprophagous was higher under additions of nitrogen.The density of Curculionidae larvae,Termiditae,Oribatida,Nematode,Onychiuridae,Sciaridae larvae,Ceratopogonidae larvae,Mycetobiidae larvae increased(P<0.05).(2)Litter multiplications did not change N2 and N3 on the promotion of soil fauna,the effect of N1 on soil fauna density and group numbers was significantly enhanced by double litter multiplication(P<0.05).Under the same concentration of nitrogen,the double litter multiplication had a significant effect on soil fauna density and group numbers(P<0.05).Litter removal significantly decreased soil fauna density and group numbers(P <0.05).The density of soil fauna with different litter multiplications: double litter multiplication> control> litter removal,double litter multiplication for soil fauna to provide habitat and food sources,as well as changes in soil physical and chemical properties,increasing the group numbers of predatory,saprophagous,fungivore soil fauna(P<0.05),and increasing the density of Oribatida,Prostigmata.The litter removal was significantly decreased the density of Oribatida(P<0.05),and it was not beneficial to the Formicidae,Therevidae larvae,Coleoptera larvae.The group numbers of Diptera larvae,Coleoptera larvae,saprophagous and predatory soil fauna was decreased under the removal of litter multiplication.(3)The contents of NO3--N,pH,TN and SOC were significantly affected by nitrogen addition(P<0.01).Compared with N0 under N3 and N4,the contents of NO3--N increased significantly(P<0.01),the soil pH was significantly decreased(P<0.05)and the content of TN was significant increased(P<0.05).The content of SOC was significantly higher under the additions of nitrogen(P<0.05).Under the same concentration of nitrogen addition,the contentsof NH4+-N and NO3--N significantly increased by litter multiplications(P<0.05).The contents of MBC,SOC and TN were significantly increased(P<0.05),the C/N was significantly decreased(P<0.05)by double litter multiplication.The soil pH was significantly decreased(P<0.01),the MBC was significantly decreased(P<0.05),and the C/N was significantly increased(P<0.05)under litter removal multiplication.Nitrogen treatments and litter multiplications both have influenced soil fauna by altering the microenvironment of the soil and the complex food web structure.