氮沉降和降水变化对荒漠草原土壤氨氧化细菌群落的影响

Effects of nitrogen deposition and precipitation changes on the soil ammonia-oxidizing bacteria community in desert steppe

为研究氮沉降和降水变化对土壤氨氧化细菌(AOB)群落的影响.以短花针茅荒漠草原为研究对象,采用裂区设计,主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)3个水分梯度,副区为0(N0/CK),30(N30),50(N50)和100(N100)kg/(hm^(2)∙a)4个氮素梯度共12个处理,通过高通量测序分析土壤氨氧化细菌群落的多样性和组成.结果表明:荒漠草原土壤AOB主要来源于norank_d__Bacteria、unclassified_k__norank_d__Bacteria及亚硝基螺旋菌属.自然降雨下,随施氮量增加,土壤AOB-氨单加氧酶(amoA)基因拷贝数升高,减雨处理下AOB-amoA基因拷贝数在N50处理显著增高,而AOB-amoA基因拷贝数在N100处理显著下降,表明在短花针茅荒漠草原地区N50处理为土壤AOB数量的阈值.增雨促进了Alpha多样性增加,并且通过主坐标分析表明氮素添加后,土壤AOB群落结构在不同处理之间存在显著差异.RDA分析表明土壤含水量、硝态氮、铵态氮及全氮是驱动土壤AOB群落变化的主要环境因子.

To explore the effects of nitrogen deposition and precipitation changes on the soil ammonia-oxidizing bacteria(AOB)community,we conducted a split-plot experiment in a desert steppe dominated by Stipabreviflora.The main plots include three water regimes:natural rainfall(CK),a 30%increase in rainfall(W),and a 30%decrease in rainfall(R).The subplots were treated with four nitrogen levels:0(N0/CK),30(N30),50(N50),and 100(N100)kg/(hm^(2)·a).High-throughput sequencing was utilized to assess the diversity and composition of the soil AOB community.Our findings revealed that the dominant AOB in the desert steppe soils are norank_d__Bacteria,unclassified_k__norank_d__Bacteria,and the genus Nitrosospira.Under natural rainfall conditions,the AOB-amoA gene copy number increased with higher nitrogen application.However,in the reduced rainfall treatment,the AOB-amoA gene copy number significantly rose at the N50 level but sharply declined at the N100 level,suggesting that N50 is a threshold for soil AOB abundance in the desert steppe.Furthermore,higher alpha diversity was associated with increased rainfall.Significant differences in soil AOB community structure across the various nitrogen treatments were revealed by principal coordinate analysis.Redundancy analysis identified soil moisture content,nitrate nitrogen,ammonium nitrogen,and total nitrogen as the key environmental factors driving changes of the soil AOB community.