长期施肥对土nir S型反硝化细菌的影响及其与N_(2)O排放的关系

Effect of Long-Term Fertilization on nir S-Type Denitrifer and Its Relationship with N_(2)O Emission in Eum-Orthic Anthrosols

土壤反硝化作用是土壤N_(2)O产生的重要过程,亚硝酸盐还原酶(NIR)催化的亚硝态氮(NO_(2))还原为一氧化氮(NO)是反硝化作用的关键环节,研究长期施肥对反硝化微生物的影响及其与N_(2)O排放的关系对于全面理解土壤反硝化过程具有重要意义。基于28年的旱作雨养长期施肥试验,通过常规监测、定量PCR和高通量测序等探讨了长期不同施肥(不施肥CK、偏施肥的单施氮肥N和氮钾配施NK、以及氮磷钾平衡施肥NPK)下土N_(2)O排放和nir S反硝化细菌群落特征及两者之间的关系。结果表明:长期化肥施用(N,NK和NPK)均显著提高了N_(2)O累积排放量,其中平衡施肥(NPK)最高。长期化肥施用对nir S基因丰度和nir S型反硝化细菌的α-多样性无显著影响,但长期平衡施用化肥提高了uncultured_bacterium_2303和Rhodanobacter_sp._D206a的相对丰度,降低了unclassified_k_norank_d_Bacteria和unclassified_p_Proteobacteria的相对丰度,从而改变了nir S型反硝化细菌的群落结构组成。雨养旱作条件下,土壤有机碳(SOC)、全氮(TN)、有效磷(AP)和pH等土壤性质是土nir S型反硝化细菌群落结构组成变化的主要影响因素。土nir S型反硝化细菌群落结构组成对土壤N_(2)O排放具有显著影响,而nir S基因丰度和nir S型反硝化细菌多样性并没有显著影响。

Soil denitrification is an important process for the production of soil N_(2)O,and that Nitrite reductase(NIR)catalyzes the reduction of nitrite nitrogen(NO_(2))to nitric oxide(NO)is the key step of denitrification.The study on the impact of long-term fertilization on denitrifying microorganisms and its relationship with soil N_(2)O emissions is of great significance for a comprehensive understanding of the soil denitrification process.Based on 28 years of long-term fertilization experiments in rain-fed dry farming system,the characteristics of soil nir S-type denitrifying bacterial communities and N_(2)O emission and their relationship were investigated under different types of long-term fertilization(No fertilization of CK,only N fertilization and NK combined fertilization of partial fertilizations,and balanced fertilization of NPK)by conventional monitoring,quantitative PCR and high-throughput sequencing.The results showed that all types of long-term fertilization(N,NK and NPK)significantly increased the cumulative N_(2)O emission(EN_(2)O),in which balanced fertilization(NPK)caused the the highest cumulative N_(2)O emission;long-term fertilization had no significant effect on nir S gene abundance and theα-diversity of nir S-type denitrifying bacteria,while long-term balanced fertilization increased the relative abundance of uncultured_bacterium_2303 and Rhodanobacter_sp._D206a,and reduced the relative abundance of unclassified_k_norank_d_Bacteria and unclassified_p_Proteobacteria,thereby changed the community structure of nir S-type denitrifying bacteria.Soil properties such as soil organic carbon,total nitrogen,available phosphorusand pH are the main factors influencing the nirS-type denitrifying bacterial community structure that has a significant effect on soil N_(2)O emission,while the abundance of nir S gene abundance and the diversity of nir S-type denitrifying bacteria have no significant effects in Eum-Orthic Anthrosols under rain-fed dry farming system.