甘肃民勤荒漠区两种主要固沙植物影响下的土壤细菌群落分布特征研究

旨在研究荒漠化区域土壤细菌群落受优势固沙植物影响下的分布特征及土壤细菌群落多样性。采集民勤的固定沙地、半固定沙地及流动沙地上白刺(Nitraria tangutorum Bobr)和梭梭(Haloxylon ammodendron)的根际及非根际土壤,通过土壤理化性质分析了解造成微生物群落变异的关键因素,并利用Illumina MiSeq 250高通量测序技术,对土壤细菌16Sr DNA的V4+V5区进行测序,分析土壤细菌群落多样性。在所有土壤样品中均存在放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、浮霉菌门(Planctomycetes)、绿弯菌门(Chloroflexi)和酸杆菌门(Acidobacteria)等菌门,主要菌属为乳球菌属(Lactococcus)、芽孢杆菌属(Bacillus)、节细菌属(Arthrobacter)、Subgroup6norank、Nitrosomonadaceaeuncultured、类诺卡氏菌属(Nocardioides)和土壤芽孢杆菌属(Solibacillus)。研究发现在该区域优势固沙植物白刺和梭梭植物根际分泌物是影响土壤细菌群落分布的重要因素,根际细菌群落结构与非根际土壤细菌群落结构相比具有显著差异,然而两种植物与不同沙地间差异不显著。根际与非根际样品间存在大量共有的OTU(Operational Taxonomic Units),同时在根际中存在大量特有的OTU。对土壤细菌群落与主要环境因子的冗余分析结果显示3个沙丘的根际土壤样品具有接近的土壤性质及细菌群落特征,并与K^+、Ca^2+离子负相关,而非根际土壤样品在土壤性质及细菌群落结构上差异较大,这与沙土及电导率呈正相关。得出固沙植物可以通过根系分泌物对其根际土壤细菌群落进行调节,并体现出了对特定菌群的选择作用。与非根际相比,根际土壤中具有更高丰度的放线菌门、拟杆菌门和变形菌门,而非根际土壤中的浮霉菌门相对丰度高于根际土壤。研究位点是否定植有固沙植物是决定土壤细菌群落形成的首要因素,沙地类型是次要因素,而寄主植物类型的影响不显著。研究该区域优势固沙植物影响下的土壤细菌群落分布特征,可为民勤沙漠化地区的生态恢复提供重要的理论依据。

Research on the Distribution Characteristics of Soil Bacteria Communities under the Influence of Two Main Sand-fixing Plants in Minqin Desert Area of Gansu Province

To study the distribution characteristics and diversity of soil bacterial community under the influence of dominant sand-fixing plants in desertification areas.The rhizosphere and bulk soils of Nitraria tangutorum Bobr.and Haloxylon ammodendron on fixed sandy land,semi-fixed sandy land and moving sandy land in Minqin were collected.Through the analysis of soil physical and chemical properties to understand the key factors causing microbial community variation,and by using IlluminaMiSeq250 high-throughput sequencing technology,the V4+V5 region of soil bacteria 16 S rDNA was sequenced to analyze the diversity of soil bacterial community.Actinobacteria,Firmicutes,Proteobacteria,Bacteroidetes,Planctomycetes,Chloroflexi and Acidobacteria were found in all soil samples.The main bacteria genera were Lactococcus,Bacillus,Arthrobacter,Subgroup6norank,Nitrosomonadaceaeuncultured,Nocardioides and Solibacillus.The study found that the rhizosphere exudates of dominant sand-fixing plants in this region were an important factor affecting the distribution of soil bacterial community,and the structure of rhizosphere bacterial community was significantly different from that of bulk soil,but there was no significant difference between the two plants and different sandy land.There were a large number of common OTU(Operational Taxonomic Units)between rhizosphere and bulk soil samples,and a large number of unique OTU in rhizosphere.The results of redundancy analysis of soil bacterial community and main environmental factors show that the rhizosphere soil samples of the three dunes had similar soil properties and bacterial community characteristics,and were negatively correlated with K+and Ca2+,while the bulk soil samples were significantly different in soil properties and bacterial community structure,which was positively correlated with sand and electrical conductivity.Sand-fixing plants can regulate the bacterial community of rhizosphere soil through the exudates of root system,and show the selective effect on the specific flora.Compared with the bulk soil,Actinobacteria,Proteobacteria and Bacteroidetes with higher abundance were found in the rhizosphere soil,while the relative abundance of Planctomycetes in the bulk soil was higher than that in the rhizosphere soil.Whether the studied sites were colonized with sand-fixing plants was the primary factor determining the formation of soil bacterial community,sandy land type was a secondary factor,however,the influence of host plant type was not significant.The study on the distribution characteristics of soil bacterial community under the influence of dominant sand-fixing plants in this area provides an important theoretical basis for the ecological restoration of desertification areas in Minqin.