三峡库区消落带落羽杉人工林土壤细菌群落结构多样性及动态变化

Structural Diversity and Its Temporal Variation in the Soil Bacterial Community Under Plantations of Taxodium distichum in the Riparian Zone of the Three Gorges Reservoir Area

消落带是连接陆地与水域的交错地带,具有重要的生态功能,其适生木本植物的种植对消落带土壤的生物地球化学循环起着重要的作用.为探究适生植物对三峡库区消落带环境的适应机制,采用高通量测序技术对消落带退水后适生植物落羽杉(Taxodium distichum)不同生长时期(T1:5月、T2:7月和T3:9月)的土壤细菌群落组成及多样性进行研究,同时采用PICRUSt2对细菌功能进行预测.结果表明,土壤pH值、硝态氮、铵态氮、土壤蔗糖酶、磷酸酶和脲酶等理化指标随时间变化显著(P<0.05);土壤细菌多样性、丰富度和结构也随时间变化而变化,除Chao1以外,根际土壤细菌的α多样性均表现为:T1>T2>T3,非根际土壤细菌α多样性则表现为:T3>T1>T2.RDA分析表明,影响细菌群落的理化指标主要有土壤pH值、脲酶、铵态氮和硝态氮.所有土壤样本中共检测到细菌60门,其中以变形菌门和酸杆菌门为优势细菌门.根据PICRUSt2预测,代谢是落羽杉土壤细菌群落中普遍存在的基本功能,与C、N和P有关的各代谢途径存在一定的时间差异.以上研究结果有助于加深对三峡消落带植被修复后土壤微生物群落特征的认识.

The riparian zone supports important ecological functions and acts as an ecotone connecting terrestrial and aquatic areas.Soil microbes under the revegetation of woody species are crucial to the biogeochemical cycle of nutrients.Here,soil samples were collected to examine the soil microbes during different emergence phases in 2019(May:T1,July:T2,and September:T3)in the riparian zone of the Three Gorges Reservoir,China.The variations in the bacterial community were evaluated using high-throughput sequencing.The results showed that:during the emergence phases,soil properties such as pH value(pH),ammonium nitrogen(NH_(+)^(4)-N),and nitrate-nitrogen(NO_(3)^(-)-N)and soil enzymes changed significantly(P<0.05),and soil bacterialαdiversity also changed with time.Except for the Chao1 index,the richness of rhizosphere soil bacteria showed T1>T2>T3,whereas theαdiversity of non-rhizosphere soil bacteria showed T3>T1>T2.The redundancy analysis(RDA)test implied that soil urease,NH_(+)^(4)-N,pH,and NO_(3)^(-)-N were the key factors structuring the microbial community.Proteobacteria and Acidobacteria were the two dominant components among the 60 phyla that were detected in the soil.Based on phylogenetic investigation of communities by reconstruction of unobserved states(PICRUSt2)prediction,metabolism was the basic function of soil bacterial communities of Taxodium distichum;in the secondary functional layer,the metabolic pathways related to carbon,nitrogen,and phosphorus mainly included amino acid metabolism,carbohydrate metabolism,lipid compound metabolism,and energy metabolism,and the relative abundance of each metabolic function had a certain time difference in different periods.These findings could help us better understand how soil microbes change after restoring vegetation in the Three Gorges Reservoir area.