不同林分土壤中氨氧化微生物的群落结构和硝化潜势差异及其驱动因子

The difference of ammonia-oxidizing microorganism communities structure and nitrification potential in soils of different forest stands and their driving factors

【目的】探究人为干扰较多的果园和观赏林土壤中氨氧化微生物的群落结构和硝化潜势差异及影响因素,为深入了解不同林分氮循环规律提供参考依据。【方法】以四川省南充市6种林分土壤(凤垭山和西山森林土壤及枇杷园、竹林、梨园、芭蕉园土壤)为研究对象,进行硝化潜势测定,以及基于氨氧化微生物amoA基因的荧光定量PCR和测序分析,并耦合土壤理化性质进行冗余分析。【结果】土壤有机质、总氮和硝态氮(NO3--N)含量及硝化潜势在不同林分土壤中差异显著(P<0.05,下同),土壤硝化潜势在7.01～59.88 mg/(kg·d),以森林土壤的硝化潜势最高,改耕为单一果林和观赏林后硝化潜势显著降低。6种土壤的氨氧化古菌(AOA)丰度(1.88×108～10.8×108copies/g干土)均高于氨氧化细菌(AOB)(2.87×107～27.6×107copies/g干土),AOA/AOB丰度比值为1.25～15.00,且该比值与土壤有机质含量呈显著负相关。相关性分析结果表明,土壤有机质和总氮含量与AOA菌群结构分别呈极显著(P<0.01)和显著相关,而土壤有机质含量与AOB菌群结构呈显著相关。冗余分析结果表明,不同土壤中AOA和AOB群落结构有所差异,6种土壤中的主导AOA菌群隶属于陆地分支Group 1.1b的54d9-like cluster,AOB的主导菌群隶属于Nitrosospira cluster 3。【结论】在土壤理化性质和硝化潜势显著差异的不同林分土壤中,氨氧化微生物群落结构存在明显的分异特征,土壤总氮和有机质为其主导驱动因子。

【Objective】The difference and influencing factors of ammonia-oxidizing microorganisms communities structure and nitrification potential in highly human-disturbed orchard and ornamental forest soils were explored in this study to provide references for thorough understanding of nitrogen cycling mechanism in different forest stands.【Method】Six forest stands soils in Nanchong,Sichuan,including soils from Fengya Mountain and Western Mountain and soils from loquat orchard,bamboo forest,pear orchard and plantain orchard,were used as research objects.The six soils were determined by nitrification potential,fluorescence quantitative PCR on basis of amoA gene in ammonia-oxidizing microorgaisms and sequencing analysis.And redundancy analysis was coupled to analyze soil physiochemical properties.【Result】Soil organic matter(SOM),total nitrogen(TN),nitrate nitrogen(NO3--N)contentsand nitrification potentialwere significantly different in the six soils(P<0.05,the same below).Soil nitrification potential ranged from 7.01 to 59.88 mg/(kg·d).The highest nitrification potential was found in the forest soils.The nitrification potential decreased significantly after the change of tillage to single-function fruit forest and ornamental forest.The abundances of ammonia-oxidizing archaea(AOA)(1.88×10^8/10.8×10^8 copies/g dry soil)in the six soils were predominant over that(2.87×10^7-27.6×10^7 copies/g dry soil)of ammonia-oxidizing bacteria(AOB).The AOA/AOB value varied from 1.25 to 15.00,and it had significant negative correlation with SOM.Correlation analysis indicated that SOM and TN contents showed extremely significant(P<0.01)and significant correlation with the change of AOA bacterial community structure respectively while SOM content showed significant correlation with AOB bacterial community structure.Redundancy analysis indicated that AOA and AOB communities structure varied among different soils.The dominant bacterial community of AOA in the six soils belonged to land branch Group 1.1b 54d9-like cluster and the dominant bacterial community of AOB belonged to Nitrosospira cluster 3.【Conclusion】In the different forest stand soils with distinct differences in soil physiochemicalproperties and nitrification potential,the ammonia-oxidizing microorganism communities structure shows great differentiation characteristics;and SOM and TN contents are the main driving factors.