Shi Jia-Mian, Song Ge, Liu Shan-Shan, Zheng Yong
Key Laboratory for Humid Subtropical Eco-geographi-cal Processes of the Ministry of Education, Fujian Normal University, Fuzhou 350117, China.
School of Geographi-cal Sciences, Fujian Normal University, Fuzhou 350117, China.
Ying Yong Sheng Tai Xue Bao. 2023 Dec;34(12):3291-3300. doi: 10.13287/j.1001-9332.202312.017.
Arbuscular mycorrhizal (AM) fungi play an important role in plant nutrient absorption and stress resistance. AM fungal spore-associated bacteria are essential for mycorrhizal colonization, but their responses to environmental changes remain largely unknown. We collected surface soil samples from a Chinese fir plantation in both summer and winter to investigate the responses of AM fungal morphological traits and spore-associated bacterial communities to simulated nitrogen deposition (40 kg N·hm·a addition) and drought (-50% precipitation exclusion). Our results showed that nitrogen addition and precipitation exclusion significantly affected AM fungal spore density and extraradical hyphal length, respectively. AM fungal intraradical colonization rate, extraradical hyphal length and spore density were significantly differed between the two seasons. Compared to control (no nitrogen addition and no precipitation exclusion treatment), both nitrogen addition and precipitation exclusion significantly reduced spore density in winter, while precipitation exclusion alone and the combined nitrogen addition and precipitation exclusion significantly increased extraradical hyphal length in summer. The dominant spore-associated bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Planctomycetes. Nitrogen addition and precipitation exclusion did not affect the diversity of spore-associated bacteria. However, the combined nitrogen addition and precipitation exclusion treatment altered the composition of the bacterial community, with significant variations between the two seasons. The spore-associated bacterial diversity was significantly higher and community variability (or turnover) was lower during summer than winter. Soil total nitrogen, nitrate nitrogen and dissolved organic carbon were important factors influencing the bacterial community composition. In all, the effects of nitrogen addition and precipitation exclusion on the morphological traits of AM fungi are seasonally dependent. The combination of nitrogen addition and precipitation exclusion has a significant impact on AM fungal spore-associated bacterial community structure.
丛枝菌根（AM）真菌在植物养分吸收和抗逆性方面发挥着重要作用。AM真菌孢子相关细菌对于菌根定殖至关重要，但其对环境变化的响应仍 largely未知。我们在夏季和冬季从一个杉木人工林中采集了表层土壤样本，以研究AM真菌形态特征和孢子相关细菌群落对模拟氮沉降（添加40 kg N·hm·a）和干旱（排除50%降水）的响应。我们的结果表明，添加氮和排除降水分别显著影响了AM真菌的孢子密度和根外菌丝长度。AM真菌的根内定殖率、根外菌丝长度和孢子密度在两个季节之间存在显著差异。与对照（不添加氮和不排除降水处理）相比，添加氮和排除降水在冬季均显著降低了孢子密度，而仅排除降水以及添加氮和排除降水的组合在夏季显著增加了根外菌丝长度。孢子相关细菌的优势菌门为变形菌门、酸杆菌门、放线菌门、绿弯菌门和浮霉菌门。添加氮和排除降水并未影响孢子相关细菌的多样性。然而，添加氮和排除降水的组合改变了细菌群落的组成，在两个季节之间存在显著差异。夏季孢子相关细菌的多样性显著高于冬季，且群落变异性（或周转率）低于冬季。土壤总氮、硝态氮和溶解有机碳是影响细菌群落组成的重要因素。总之，添加氮和排除降水对AM真菌形态特征的影响具有季节依赖性。添加氮和排除降水的组合对AM真菌孢子相关细菌群落结构有显著影响。
