亚热带常见造林树种对土壤细菌及微生物功能群的影响

为揭示亚热带人工林常见造林树种对森林土壤微生物群落的影响,本研究选取马尾松、米老排、枫香、冬青、火力楠、麻栎和光皮桦7个树种为研究对象,采用16S rRNA高通量测序和实时荧光定量PCR技术,探究不同树种土壤细菌的多样性、群落构成以及微生物功能群基因丰度。结果表明: 变形菌门、酸杆菌门和放线菌门是亚热带造林树种的优势细菌门,不同树种细菌多样性和丰富度指数无显著差异。冗余分析表明,土壤容重、土壤C/N、凋落物氮和凋落物C/N是影响土壤细菌组成的主要环境因子。不同造林树种土壤中氨氧化古菌、氨氧化细菌和完全氨氧化菌amoA基因丰度均具有显著差异。完全氨氧化菌在数量上占据优势地位,但只有氨氧化古菌amoA基因丰度与土壤硝态氮呈显著正相关关系,表明氨氧化古菌在亚热带酸性森林土壤自养硝化作用中可能发挥主要作用。相关分析表明,凋落物氮是不同树种影响氨氧化微生物丰度变化的关键驱动因子。本研究表明,土壤微生物功能群对树种的响应比细菌群落结构更加敏感,未来应从微生物功能群角度深入探究不同造林树种对森林生态系统功能的影响机制。

Effects of common afforestation tree species on soil bacterial community and microbial functional guilds in subtropical forests

To understand the effects of common afforestation tree species on soil microbial community in subtropical forests, seven different tree species were selected as the research object, including Pinus massoniana, Mytilaria laosensis, Liquidambar formosana, Ilex chinensis, Michelia macclurei, Quercus acutissima and Betula luminifera. Based on 16S rRNA high-throughput sequencing and real-time quantitative PCR techniques, we explored the effects of different tree species on soil bacterial community composition, diversity and microbial functional guilds. The results showed that Acidobacteria, Proteobacteria, and Actinobacteria were the dominant bacterial phyla, and that there was no significant difference in bacterial diversity or richness index among different tree species. Results of redundancy analysis suggested that soil bulk density, soil C/N, litter nitrogen content, and litter C/N were the predominant factors determining soil bacterial community composition. The afforestation tree species had significant effects on functional gene abundances of ammonia oxidizing archaea, ammonia oxidizing bacteria and complete ammonia oxidation. Comammox were dominant in abundance. Ammonia oxidizing archaea amoA gene was the only type whose abundance showed significant correlation with soil nitrate content, suggesting that ammonia oxidizing archaea could play a dominant role in the autotrophic nitrification in the acidic subtropical forest soils. The afforestation tree species had significant effects on functional gene abundances of ammonia oxidizing microorganisms. Results of correlation analysis showed that litter nitrogen content was the driving factor for the abundance of ammonia oxidizing microorganisms. Our study provided strong evidence that the responses of soil microbial functional guilds to tree species were more sensitive than bacterial community composition. Future studies should explore the mechanisms of tree plantations on forest ecosystem functioning from the perspective of microbial functional guilds.