火干扰对油松林土壤细菌群落的影响

Effects of fire disturbance on soil bacterial community in Pinus tabuliformis forest

以河北省平泉市油松天然次生林火烧迹地的土壤细菌群落为对象,利用高通量测序技术(16S rRNA)测定不同火强度样地土壤样品的OTU,并在不同分类水平进行注释,分析细菌优势群体在对照样地、轻度火烧样地、中度火烧样地、重度火烧样地的数量变化特征,并综合土壤理化性质(有机碳、铵态氮、硝态氮、速效磷、含水率、pH)、土壤酶活性(脲酶、蛋白酶、过氧化氢酶、脱氢酶),分析火干扰后土壤微环境变化和土壤细菌群落的关系。结果表明:不同火强度改变细菌群落构成,门水平上以变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、疣微菌门(Verrucomicrobia)、绿弯菌门(Chloroflexi)为优势群体。属水平上以Candidatus_Udaeobacter(疣微菌门、Chthoniobacterales目)、慢生根瘤菌(Bradyrhizobium,变形菌门、根瘤菌目)、RB41(酸杆菌门、Pyrinomonadales目)、uncultured_Acidobacteria_bacterium(酸杆菌门、嗜邻聚杆菌目)、分枝杆菌(Mycobacterium,放线菌门、Corynebacteriales目)为优势群体。火干扰对细菌群落分布具有显著影响,不同火强度分组之间的差异显著(P<0.05)。Alpha多样性指标中,Chao1在中度火烧样地最高,Observed_species在轻度火烧样地最高,PD_whole_tree和香农指数在轻度、中度和重度火烧样地普遍高于对照样地。中度火烧有助于维持群落较高多样性,重度火烧则增加群落异质性导致生境破碎化,在多年后仍具有影响;脲酶和脱氢酶活性对不同火强度样地细菌群落组成具有最大解释度,脲酶活性与Candidatus_Udaeobacter、uncultured_Acidobacteria_Bacteria、RB41高度正相关,脱氢酶活性与Candidatus_Solibacter、苔藓杆菌、慢生根瘤菌和uncultured_Acidobacteria_Bacteria高度正相关。

High⁃throughput sequencing technology(16S rRNA)was used to measure OTU of soil bacterial commu⁃nity in plots with different fire intensities(no fire(control),light intensity,moderate intensity,and high intensity)in a secondary Pinus tabuliformis forest in Pingquan City,Hebei Province.OTUs were annotated at different taxonomic levels,which were used to analyze the quantitative changes of dominant soil bacterial groups under differ⁃ent fire intensities.Soil physicochemical properties(soil organic carbon,NH4+⁃N,NO3-⁃N,available phosphorus,water content,pH)and soil enzyme activity(urease,protease,catalase,and dehydrogenase)were used to analyze the relationship between soil microenvironment changes and soil bacterial communities after fire disturbance.The re⁃sults showed that the composition of bacterial community varied across different fire intensities.At the phylum level,Proteobacteria,Acidobacteria,Actinobacteria,Verrucomicrobia,Chloroflexi dominated the communities.At the genus level,Candidatus_Udaeobacter(Verrucomicrobia,Chthoniobacterales),Bradyrhizobium(Proteobacteria,Rhizobiales),RB41(Acidobacteria,Pyrinomonadales),uncultured_Acidobacteria_bacterium(Acidobacteria,Vic⁃inamibacterales),Mycobacterium(Actinobacteria,Corynebacteriales)dominated the communities.Fire disturb⁃ance had a significant effect on the distribution of bacterial communities,with significant differences among different fire intensities(P<0.05).Among the alpha diversity indices,the value of Chao1 was the highest in the moderate fire intensity plots,and Observed_species was the highest in the light fire intensity plots.PD_whole_tree and Shan⁃non index were generally higher in the light,moderate,and high fire intensity plots than in the control plots.Moderate⁃intensity fire maintained a high diversity of soil bacterial community,while high⁃intensity fire increased com⁃munity heterogeneity and led to habitat fragmentation,which a legacy effect after many years.Urease and dehydro⁃genase activities had the greatest degree of interpretation for bacterial community composition in different fire inten⁃sity plots.Urease activity was highly positively correlated with Candidatus_Udaeobacter,uncultured_Acidobacteria_Bacteria,RB41.Dehydrogenase activity was highly positively correlated with Candidatus_Solibacter,Bryobacteri⁃um,Bradyrhizobia and uncultured_Acidobacteria_Bacteria.