Li Daiyan, Meng Meng, Ren Baihui, Ma Xinwei, Bai Long, Li Jiahuan, Bai Guohua, Yao Fengjun, Tan Chunming
College of Horticulture, Shenyang Agricultural University, Shenyang, Liaoning, China.
Zhangwu County Forest and Grass Development Service Center, Fuxin, Liaoning, China.
Front Microbiol. 2023 Sep 6;14:1211768. doi: 10.3389/fmicb.2023.1211768. eCollection 2023.
Continuous nitrogen deposition increases the nitrogen content of terrestrial ecosystem and affects the geochemical cycle of soil nitrogen. Forest-grassland ecotone is the interface area of forest and grassland and is sensitive to global climate change. However, the structure composition and diversity of soil microbial communities and their relationship with soil environmental factors at increasing nitrogen deposition have not been sufficiently studied in forest-grassland ecotone.
In this study, experiments were carried out with four nitrogen addition treatments (0 kgN·hm·a, 10 kgN·hm·a, 20 kgN·hm·a and 40 kgN·hm·a) to simulate nitrogen deposition in a forest-grassland ecotone in northwest Liaoning Province, China. High-throughput sequencing and qPCR technologies were used to analyze the composition, structure, and diversity characteristics of the soil microbial communities under different levels of nitrogen addition.
The results showed that soil pH decreased significantly at increasing nitrogen concentrations, and the total nitrogen and ammonium nitrogen contents first increased and then decreased, which were significantly higher in the N10 treatment than in other treatments (N:0.32 ~ 0.48 g/kg; NH-N: 11.54 ~ 13 mg/kg). With the increase in nitrogen concentration, the net nitrogen mineralization, nitrification, and ammoniation rates decreased. The addition of nitrogen had no significant effect on the diversity and structure of the fungal community, while the diversity of the bacterial community decreased significantly at increasing nitrogen concentrations. Ascomycetes and Actinomycetes were the dominant fungal and bacterial phyla, respectively. The relative abundance of Ascomycetes was negatively correlated with total nitrogen content, while that of Actinomycetes was positively correlated with soil pH. The fungal community diversity was significantly negatively correlated with nitrate nitrogen, while the diversity of the bacterial community was significantly positively correlated with soil pH. No significant differences in the abundance of functional genes related to soil nitrogen transformations under the different treatments were observed. Overall, the distribution pattern and driving factors were different in soil microbial communities in a forest-grassland ecotone in northwest Liaoning. Our study enriches research content related to factors that affect the forest-grassland ecotone.
持续的氮沉降增加了陆地生态系统的氮含量，并影响土壤氮的地球化学循环。森林草原交错带是森林和草原的交界区域，对全球气候变化敏感。然而，在森林草原交错带，氮沉降增加时土壤微生物群落的结构组成、多样性及其与土壤环境因子的关系尚未得到充分研究。
本研究设置了四个氮添加处理（0 kgN·hm·a、10 kgN·hm·a、20 kgN·hm·a和40 kgN·hm·a），以模拟中国辽宁省西北部森林草原交错带的氮沉降。采用高通量测序和qPCR技术分析不同氮添加水平下土壤微生物群落的组成、结构和多样性特征。
结果表明，随着氮浓度增加，土壤pH显著降低，全氮和铵态氮含量先增加后降低，N10处理显著高于其他处理（全氮：0.32 ~ 0.48 g/kg；铵态氮：11.54 ~ 13 mg/kg）。随着氮浓度增加，净氮矿化、硝化和氨化速率降低。添加氮对真菌群落的多样性和结构无显著影响，而随着氮浓度增加，细菌群落的多样性显著降低。子囊菌门和放线菌门分别是优势真菌和细菌门类。子囊菌门的相对丰度与全氮含量呈负相关，而放线菌门的相对丰度与土壤pH呈正相关。真菌群落多样性与硝态氮显著负相关，而细菌群落多样性与土壤pH显著正相关。不同处理下与土壤氮转化相关的功能基因丰度未观察到显著差异。总体而言，辽宁省西北部森林草原交错带土壤微生物群落的分布格局和驱动因素不同。我们的研究丰富了影响森林草原交错带因素的相关研究内容。
