Ren Baihui, Ma Xinwei, Li Daiyan, Bai Long, Li Jiahuan, Yu Jianxin, Meng Meng, Li Haoyan
College of Horticulture, Shenyang Agricultural University, Shenyang, China.
Front Microbiol. 2024 May 30;15:1290248. doi: 10.3389/fmicb.2024.1290248. eCollection 2024.
The impact of nitrogen (N) deposition on the soil N-transforming process in grasslands necessitates further investigation into how N input influences the structural composition and diversity of soil N-cycling microbial communities across different grassland types.
In this study, we selected two types of grassland soils in northwest Liaoning, temperate steppe and warm-temperate shrub, and conducted short-term N addition experiments using organic N, ammonium N, and nitrate N as sources with three concentration gradients to simulate N deposition. Illumina MiSeq sequencing technology was employed to sequence genes associated with N-cycling microbes including N-fixing, ammonia-oxidizing and denitrifying bacteria, and ammonia-oxidizing archaea.
The results revealed significant alterations in the structural composition and diversity of the N-cycling microbial community due to N addition, but the response of soil microorganisms varied inconsistent among different grassland types. Ammonium transformation rates had a greater impact on soils from temperate steppes while nitrification rates were more influential for soils from warm-temperate shrubs. Furthermore, the influence of the type of N source on soil N-cycling microorganisms outweighed that of its quantity applied. The ammonium type of nitrogen source is considered the most influential driving factor affecting changes in the structure of the microbial community involved in nitrogen transformation, while the amount of low nitrogen applied primarily determines the composition of soil bacterial communities engaged in nitrogen fixation and nitrification. Different groups of N-cycling microorganisms exhibited distinct responses to varying levels of nitrogen addition with a positive correlation observed between their composition, diversity, and environmental factors examined. Overall findings suggest that short-term nitrogen deposition may sustain dominant processes such as soil-N fixation within grasslands over an extended period without causing significant negative effects on northwestern Liaoning's grassland ecosystems within the next decade.
氮（N）沉降对草原土壤氮转化过程的影响，使得有必要进一步研究氮输入如何影响不同草原类型土壤氮循环微生物群落的结构组成和多样性。
在本研究中，我们选择了辽宁西北部的两种草原土壤，温带草原和暖温带灌丛，以有机氮、铵态氮和硝态氮为氮源，设置三个浓度梯度进行短期氮添加实验，以模拟氮沉降。采用Illumina MiSeq测序技术对与氮循环微生物相关的基因进行测序，包括固氮菌、氨氧化细菌、反硝化细菌和氨氧化古菌。
结果表明，氮添加导致氮循环微生物群落的结构组成和多样性发生显著变化，但不同草原类型土壤微生物的响应不一致。铵转化速率对温带草原土壤的影响更大，而硝化速率对暖温带灌丛土壤的影响更大。此外，氮源类型对土壤氮循环微生物的影响大于施用量的影响。铵态氮源被认为是影响参与氮转化的微生物群落结构变化的最主要驱动因素，而低氮施用量主要决定了参与固氮和硝化的土壤细菌群落的组成。不同组的氮循环微生物对不同水平的氮添加表现出不同的响应，其组成、多样性与所检测的环境因素之间呈正相关。总体研究结果表明，短期氮沉降可能在较长时期内维持草原土壤固氮等主要过程，在未来十年内不会对辽宁西北部的草原生态系统造成显著负面影响。
