模拟酸雨对毛竹入侵阔叶林缓冲区土壤细菌群落多样性的影响

为了分析酸雨对毛竹入侵阔叶林缓冲区土壤细菌群落多样性的影响，以浙江省天目山国家级自然保护区毛竹扩张形成的竹阔混交林为研究对象，选取T₁（pH=4.0）、T₂（pH=2.5）两个模拟酸雨梯度，并以pH=5.5为对照（CK），应用Illumina MiSeq高通量测试技术分析不同强度酸雨胁迫下土壤细菌群落组成和多样性变化及其关键影响因素.结果表明:①随着酸雨强度增加，竹阔混交林土壤w（TN）（TN为总氮）、w（OC）（OC为有机碳）、C/N和w（AN）（AN为碱解氮）显著升高，而pH、w（DOC）（DOC为可溶性有机碳）、w（MBC）（MBC微生物量碳）和w（MBN）（MBN为微生物量氮）显著下降（P < 0.05）.②与CK相比，模拟酸雨处理（T₁、T₂）显著降低了细菌群落的OTUs数量、Chao1指数和Ace指数（P < 0.05）.③竹阔混交林土壤细菌包括34门96纲247目401科698属，其中变形菌门、酸杆菌门、绿弯菌门、放线菌门为3种处理下共有的优势菌门（相对丰度>1%）.变形菌门和放线菌门相对丰度在CK处理下最高，酸杆菌门和绿弯菌门相对丰度在T₂处理下最高.与CK相比，Arthrobacter属和Elsterales属相对丰度变化显著，可作为酸雨胁迫下土壤细菌群落结构变化的指示种.主坐标（PCoA）分析和相似性检验结果显示，模拟酸雨改变了土壤细菌群落结构.④冗余分析（RDA）和相关性分析表明，不同酸雨处理的竹阔混交林土壤细菌多样性与土壤pH、w（TN）密切相关（P < 0.05）.研究显示，不同模拟酸雨处理下土壤细菌群落结构和多样性有明显差异，主要可能受到土壤pH、w（TN）的影响. 

Effects of Simulated Acid Rain on Soil Bacterial Community Diversity in Buffer Zone of Broad-Leaved Forest Invaded by Moso Bamboo

In order to determine the effect of acid rain on the diversity of bacterial community of forest soil, the typical transition zone of Moso bamboo (Phyllostachys edulis) and broad-leave mixed forests in the Tianmu Mountain Nature Reserve, Zhejiang Province, China was selected as the study object. Soil samples were collected from a mixed Moso bamboo and broad-leaved forest (or transition forest). Three gradients of simulated acid rain treatment (T₁ (pH=2.5), T₂(pH=4.0) and CK (pH=5.5)) were designed to determine the effects of simulated acid rain on soil bacterial community diversity in the transition forest. The changes of soil bacterial community composition and diversity under different acid rain stress and the key influencing factors were analyzed using Illumina sequencing. The results showed that with the increase of acid rain, soil w(TN), w(OC), C/N and w(AN) increased significantly, and soil pH, w(DOC), w(MBC) and w(MBN) reduced significantly (P<0.05). Compared with CK, simulated acid rain significantly reduced the OTU number, Chao 1 index and Ace index of bacterial community (P<0.05). Community analysis of soil bacteria identified 34 phyla, 96 classes, 247 orders, 401 families and 698 genera in the soil of Moso bamboo and broad-leave mixed forests. Among them, Proteobacteria, Acidobacteria, Chloroflexi and Actinobacteria were the predominant bacterial phyla (relative abundance of >1%) under the three treatments. The changes in soil bacterial community structure were mainly related to the in relative abundance of genus Arthrobacter and genus Elsterales could be utilized as an indicator species to indicate changes in soil bacterial community structure. The relative abundance of Proteobacteria and Actinobacteria was the highest in CK treatment, while the relative abundance of Acidobacteria and Chloroflexi was the highest in T₂ treatment. Redundancy and correlation analysis demonstrated that the relative abundance of Proteobacteria and Actinobacteria was significantly positively correlated with pH (P<0.05), and negatively correlated with w(TN) (P<0.05). The relative abundance of Chloroflexi and Actinobacteria was significantly negatively correlated with pH (P<0.05), and significantly positively correlated with w(TN) (P<0.05). These results showed the soil bacterial community and diversity were significantly different for the acid rain treatment, and provided a basis for understanding the impact of acid rain stress on bamboo invasion.