赤水河流域典型植被类型的土壤微生物群落结构与多样性

土壤微生物是反映土壤环境质量的重要指标,为明确赤水河流域典型植被类型土壤微生物群落特征及优势菌属,为生态系统的恢复与管理提供理论依据,采用高通量测序技术研究了赤水河流域的5种典型植被类型(灌丛、针阔混交林、常绿阔叶林、杉木林和竹林)土壤的微生物群落结构及多样性,并探讨了其主要影响因子。结果表明:(1)不同植被类型的细菌和真菌丰富度Chao1指数差异均不显著,说明二者所观测到的物种总数没有差异。Shannon指数显示各植被类型微生物多样性存在一定差异,细菌多样性以竹林最低,显著性低于灌丛和针阔混交林(p<0.05); 真菌多样性以灌丛和杉木林显著性高于其他3种植被类型(p<0.05)。(2)5种植被类型土壤细菌优势门(相对丰度>10%)主要有变形菌门(Proteobacteria)、放线菌门(Actinobacteriota)和酸杆菌门(Acidobacteriota)。其中变形菌门(Proteobacteria)在灌丛、针阔混交林和常绿阔叶林中占绝对优势(相对丰度为29.70%～33.62%),而放线菌门(Actinobacteriota)则在杉木林和竹林中最为丰富,相对丰度占比分别为32.88%,29.88%。各植被类型土壤真菌门以子囊菌门(Ascomycota)为绝对优势菌群(相对丰度>49%)。(3)5种植被类型土壤细菌和真菌中优势菌属差异较大。在细菌属水平上,针阔混交林和竹林分别以未定名的Vicinamibacterales和芽孢杆菌属(Bacillus)为优势,而其他3种植被类型则以节杆菌属(Arthrobacter)最丰富。在真菌属水平上,灌丛和常绿阔叶林中优势关键属为子囊菌门(Ascomycota)未分类真菌属(unclassified_p_Ascomycota),杉木林以被孢霉属(Mortierella)最丰富,而针阔混交林和竹林中均以沙蜥属(Saitozyma)相对丰度最高。(4)NMDS分析表明,土壤细菌与真菌群落空间分布差异显著。(5)冗余分析表明,土壤含水量、pH值和TN(总氮)对土壤细菌群落结构具有显著性的影响,而pH值、容重、TOC(总有机碳)、TN和TP(总磷)对真菌群落结构影响显著。综合分析可知,针阔混交林土壤细菌群落较丰富,杉木林土壤真菌生长较旺盛,而灌丛土壤细菌和真菌多样性均较高,应采取有效措施提高主要林分土壤养分,从而激发微生物的生长,改善土壤环境。

Soil Microbial Community Structure and Diversity of Typical Vegetation Types in Chishui River Basin

Soil microorganism is an important indicator of soil environmental quality. The characteristics and dominant species of soil microbial community under typical vegetation types in the Chishui River Basin were clarified in order to provide a theoretical basis for ecosystem restoration and management. In this study, high-throughput sequencing technology was used to determine the microbial community structure and diversity of soil in five typical vegetation types such as shrub(SH), mixed conifer broadleaf forest(MCBF), evergreen broad-leaved forest(EBF), Chinese fir forest(CFF)and bamboo forest(BF)and to investigate the main influencing factors. The results showed that:(1)There was no significant difference in the Chao1 index of bacteria and fungi among the different vegetation types, indicating that there was no difference in the total number of species observed among five vegetation types. The Shannon index showed that there were certain differences in microbial diversity among the five vegetation types. BF had the lowest bacterial diversity, which was significantly lower than that of SH and MCBF(p<0.05). The fungal diversity in SH and CFF was significantly higher than that in the other three planting types(p<0.05).(2)The dominant group of bacteria phylum(relative abundance>10%)in five vegetation types were Proteobacteria, Actinobacteriota and Acidobacteriota. Proteobacteria was dominant in SH, MCBF and EBF(the relative abundance ranged from 29.70% to 33.62%). But Actinobacteriota was the most abundant in CFF and BF, accounting for 32.88% and 29.88%, respectively. Ascomycota was the absolute dominant group of soil fungi in different vegetation types(with the highest relative abundance>49%).(3)The dominant genus in soil bacteria and fungi of five vegetation types were significantly different. At the genus level of bacteria, Vicinamibacterales and Bacillus were dominant in MCBF and BF, respectively. While Arthrobacter was the most dominant species in the other three vegetation types. At the fungal level, the dominant genus in SH and EBF was unclassified_p_Ascomycota. Mortierella was the most abundant taxa in CFF, while Saitozyma in MCBF and BF had the highest relative abundance.(4)NMDS analysis showed that there was significant differences in the spatial distribution of soil bacterial and fungal communities among different vegetation types.(5)Redundancy analysis showed that soil moisture content, pH value and TN had significant effects on soil bacterial community structure, while fungal community structure was significantly driven by pH, bulk density, TOC, TN and TP. Comprehensive analysis showed that MCNF had rich soil bacterial community and the growth of soil fungi in CFF was vigorous. While soil bacterial and fungal diversity were high in SH. It is necessary to take effective measures to improve soil nutrients of the main stand, to stimulate the growth of microorganisms and improve the soil environment.