Effects of Long-term Different N Application Rates on Aggregate Distribution and Fungal Community Composition in Fluvo-aquic Soil
[Objective]The aggregate distribution,the composition of the fungal community,and the production of biological binding agents can be significantly changed by different nitrogen(N)application rates.However,whether there is a correlation between these properties remains unclear.[Method]A 16-year field experiment located in Fengqiu Agro-ecological National Experimental Station was used as the research platform,and this included five levels of N application rates,i.e.(1)F0:0,(2)F1:150 kg·hm-2,(3)F2:190 kg·hm-2,(4)F3:230 kg·hm-2,and(5)F4:270 kg·hm-2.The effects of different N application rates on water-stable aggregate distribution(>2 000 µm,2 000-250 µm,250-53 µm and<53 µm)were explored,and the correlation between aggregate distribution and the major biological binding agents(glomalin-related soil proteins(GRSP)and microbial biomass carbon(MBC))and soil fungal community was studied.[Result]The soil aggregate distribution and fungal community composition were divided into three significantly different groups:F0,F1 and F2,F3 and F4,respectively.The results showed that:(1)F1 and F2 treatments had the highest mean weight diameter of soil aggregates and significantly increased the proportion of>2 000 µm aggregates and this was mainly related to the enrichment of Pyrenochaetopsis;(2)F1 and F2,F3 and F4 treatments all increased the proportion of 2 000-250 µm aggregates,while they significantly decreased the proportion of<53 µm aggregates.The increase of the proportion of 2 000-250 µm aggregates was significantly positively correlated with the ratio of easily extractable glomalin-related soil proteins to total glomalin-related soil proteins(EE-GRSP/T-GRSP)and easily extractable glomalin-related soil proteins(EE-GRSP).However,it was significantly negatively correlated with the relative abundance of Didymella and Mortierella.The decrease of the proportion of<53 µm aggregates was significantly positively correlated with the relative abundance of Mortierella,Phlebia,Melanospora,Fusicolla,Podospora and Didymella,but significantly negatively correlated with EE-GRSP and/or the relative abundance of Acremonium,Scytalidium and Exophiala,EE-GRSP/T-GRSP and MBC.[Conclusion]The variation of soil aggregate stability was affected by the level of N application.Also,the stability of soil aggregates under N application rates of 150 kg·hm-2 and 190 kg·hm-2 was higher than that under N application rates of 230 kg·hm-2 and 270 kg·hm-2,which was significantly correlated with the changes in fungal community composition and biological binding agents under different N application rates.
Long-term experimentNitrogen application ratesAggregate stabilityBiological binding agentsFungal community
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