外源氮素调控碳氮比对杉木林凋落叶细菌群落结构的影响

为探究不同碳氮比对杉木凋落叶分解特性的影响,通过添加外源氮,采用分解袋法,分析林下植被保留和林下植被去除2 种林分中不同碳氮比值的杉木凋落叶分解300 d 时细菌群落结构差异。研究显示一定范围内,初始碳氮比降低有利于杉木凋落叶分解和细菌群落多样性提升,过低的碳氮比则具有抑制作用;相比于林下植被去除,林下植被保留管理措施更有利于杉木凋落叶的分解,且细菌群落多样性更高,但当初始碳氮比值为20. 3 时,杉木凋落叶分解所受的抑制作用更为明显;在门水平上,变形菌门、放线菌门和浮霉菌门为杉木凋落叶中主要优势种群;在属水平上,慢生根瘤菌属、嗜酸栖热菌属和Singulisphaera属在杉木凋落叶中相对丰度较高;不同处理间的杉木凋落叶细菌群落结构具有显著差异,变形菌门、放线菌门和酸杆菌门等细菌门中的多类细菌相对丰度差异显著;在门分类水平上,杉木凋落叶碳氮比值与主要细菌种群相对丰度的相关性最高,碳磷比值与杉木凋落叶细菌群落结构变异的相关性最高;在属水平上,杉木凋落叶全碳含量、碳氮比值和全钾含量与主要细菌种群相对丰度的相关性最高,全钾含量与杉木凋落叶细菌群落结构变异的相关性最高。结果表明初始碳氮比的降低改变了杉木凋落叶细菌群落结构,进而作用于杉木凋落叶的分解。

To investigate the effects of different C/N ratios on the decomposition characteristics of Chinese fir leaf litter, we added exogenous nitrogen, adopted the litterbag method, and analyzed the differences in bacterial community structure of Chinese fir leaf litter with varying C/N ratios under two stand management practices (retention and removal of understory vegetation) after 300 days of decomposition. The results showed that within a certain range, reducing the initial C/N ratio was conducive to the decomposition of Chinese fir leaf litter and the improvement of bacterial community diversity, while an excessively low C/N ratio had an inhibitory effect. Compared with the removal of understory vegetation, the management practice of retaining understory vegetation was more beneficial to the decomposition of Chinese fir leaf litter and had higher bacterial community diversity, but when the initial C/N ratio was 20.3, the inhibitory effect on the decomposition of Chinese fir leaf litter was more pronounced. At the phylum level, Proteobacteria, Actinobacteriota, and Planctomycetota were the main dominant populations in Chinese fir leaf litter. At the genus level, Bradyrhizobium, Acidothermus, and Singulisphaera had relatively high abundances in Chinese fir leaf litter. The bacterial community structure of Chinese fir leaf litter differed significantly among different treatments, and the relative abundances of multiple bacterial taxa within phyla such as Proteobacteria, Actinobacteriota, and Acidobacteriota showed significant differences. At the phylum classification level, the C/N ratio of Chinese fir leaf litter had the highest correlation with the relative abundances of dominant bacterial populations, while the C/P ratio had the highest correlation with the variation in bacterial community structure of Chinese fir leaf litter. At the genus level, the total carbon content, C/N ratio, and total potassium content of Chinese fir leaf litter had the highest correlations with the relative abundances of dominant bacterial populations, while the total potassium content had the highest correlation with the variation in bacterial community structure of Chinese fir leaf litter. The results indicated that reducing the initial C/N ratio altered the bacterial community structure of Chinese fir leaf litter, thereby affecting its decomposition.