贺兰山不同林分凋落物微生物群落特征与影响因素

贺兰山是我国重要生态屏障，贺兰山生态森林生态系统保护受到极大关注，森林凋落物及土壤微生物对全球气候变化研究具有重要意义。目前，贺兰山不同林分的凋落物分解过程中微生物群落结构特征差异、不同凋落物化学组成对微生物群落结构的影响尚不清楚。以贺兰山具有代表性的3种林分（油松林、青海云杉林以及油松-山杨混交林）凋落物为研究对象，开展凋落物化学组成、微生物群落组成及多样性特征研究，揭示不同林分凋落物的优势微生物群落特征和影响因子。结果表明，3种林分凋落物的细菌和真菌在多个多样性指数之间差异性均不显著，但是在多样性指数中真菌PD whole tree指数显著大于细菌，真菌Shannon指数与Ghao1指数却显著小于细菌。在门水平上不同林分凋落物的微生物优势菌类无显著差异，但在属水平上差异显著，而且细菌差异小于真菌，在各个分类水平上，凋落物细菌和真菌群落组成均表现为油松-山杨混交林＜青海云杉林＜青海云杉林，凋落物微生物多样性在青海云杉林中最为丰富。细菌不同节点间连接线负相关数量略大于正相关，真菌则相反。油松林凋落物与其它林分凋落物相比，微生物群落之间联系更加紧密。油松林凋落物OC含量最大、青海云杉林凋落物的TK含量最大、油松-山杨混交林的TN含量最大，且在3种林分中显著差异。相关性分析表明OC、TN、TP、TK是影响凋落物细菌和真菌群落组成及多样性的主要因素，冗余分析表明不同林分凋落物的微生物多样性指数受养分影响，凋落物OC、TN、TP、TK是影响微生物群落组成和多样性的重要因素，其中OC与微生物群落多样性相关性最显著，是影响凋落物细菌和真菌群落组成和多样性最主要的因子。

Microbial community characteristics and influencing factors of litter in different forest stands in Helan Mountains

Helan Mountains is an important ecological barrier in China, Enhancing the protection of ecological forest ecosystem in Helan Mountains has received great attention. Litter is the main source of soil nutrients, and forest litter and soil microorganisms are of great significance to the study of global climate change, while Difference of microbial community structure in litter decomposition of different forest types in Helan Mountains and the influence of different litter physical and chemical groups on microbial community structure are not fully revealed. In this study, composition and diversity characteristics of microbial communities in litter of Qinghai spruce forest, and Pinus tabulaeformis, and mixed forest of Pinus tabulaeformis and Populus davidiana were studied, sampling routine methods and high throughput sequencing methods were used to reveal difference in chemical composition, microbial community composition and diversity characteristics, and explore impact factors of advantage. Results showed that organic carbon content was the largest in the three kinds of forest litters, total phosphorus, the contents of organic carbon, total nitrogen and total potassium in the litter of Pinus tabulaeformis forest, coniferous and broad-leaved mixed forest and Picea crassifolia forest were the largest, and the differences were significant. The C/N and C/P ratios of the litter of Pinus tabulaeformis forest were significantly higher than those of the other two stands, and the value of N/P ratio of the litter of Picea crassifolia forest was significantly lower than that of the other two stands. There was no significant difference in dominant fungi at phylum level among different stands, but there was significant difference at genus level, and the difference of fungi was greater than that of bacteria. At each classification level, the composition of bacteria and fungi community was as follows:coniferous and broadleaved mixed forest