洮河上游不同海拔紫果云杉根际与非根际土壤细菌多样性及影响因子

Diversity and influencing factors of bacteria in rhizosphere and non-rhizosphere soil of Picea purpurea at different altitudes in the upstream of Taohe river

摘要:

【背景】紫果云杉天然林在维护洮河上游生态环境安全方面发挥着重要作用，不同海拔梯度如何影响紫果云杉根际与非根际细菌多样性、土壤养分因子及三者之间的相关性尚不清楚。【目的】深入探索紫果云杉根际与非根际土壤细菌群落结构组成及受控因子。【方法】采用Illumina Miseq平台对洮河上游不同海拔紫果云杉天然林根际与非根际土壤细菌进行测序分析，分析土壤理化因子与细菌多样性随海拔的变化趋势，并通过相关性与冗余分析探究环境因子对细菌群落的影响。【结果】土壤养分因子随海拔升高呈先增加后降低趋势；根际土养分因子组间差异显著(P<0.05)，非根际组间差异不显著(P>0.05)。随海拔升高根际微生物物种多样性指数(H)、均匀度指数(E)、丰富度指数(Chao1/ACE)和OTU数目呈单峰型变化趋势；非根际多样性指数随海拔升高呈双峰型变化趋势。土壤细菌多样性与养分因子密切相关，其中有机质、全氮和碱解氮呈显著正相关(P<0.05)，而土壤pH和有效磷与细菌多样性呈负相关但不显著(P>0.05)。不同海拔梯度下紫果云杉天然林细菌群落结构一致性较高，从30个样本中获得7 159个细菌OTU，注释到37个门；细菌优势类群为放线菌门、变形菌门、酸杆菌门和绿弯菌门。不同细菌门对土壤养分因子的响应各不相同，有机质、全氮和碱解氮与变形菌门呈显著正相关(P<0.05)。【结论】土壤理化因子能够显著影响紫果云杉根际与非根际细菌多样性和组成，海拔和水热条件等环境因子对植物和土壤的驱动影响是细菌群落结构稳定组成的重要原因。本研究有助于深入理解紫果云杉天然林土壤细菌多样性的变化和驱动机制，为洮河上游天然林恢复与生态恢复提供借鉴。

Abstract:

[Background] The natural forest dominated by Picea purpurea plays an important role in maintaining ecological security in the upstream of Taohe river. It is still unclear how altitude influences the bacterial diversity and nutrients in rhizosphere and non-rhizosphere soil of P. purpurea, and how the altitude, soil nutrients, and bacterial diversity interact with each other. [Objective] To explore the community structures of bacteria in rhizosphere and non-rhizosphere soil of P. purpurea and the influencing factors.[Methods] Illumina Miseq was employed for sequence analysis of the rhizosphere and non-rhizosphere bacteria in the natural P. purpurea forest at different elevations in the upper reaches of Taohe river. The changes of soil physical and chemical factors and bacterial diversity with altitude were analyzed. Correlation and redundancy analysis was performed to elucidate the effect of some environmental factors on bacterial community. [Results] The nutrients of rhizosphere and non-rhizosphere soil samples of P. purpurea increased first and then decreased with the rise of altitude. The intergroup difference was significant for rhizosphere soil nutrients (P<0.05) but insignificant for non-rhizosphere soil nutrients (P>0.05). The rhizosphere species diversity index (H), evenness index (E), richness index (Chao1/ACE), and number of operational taxonomic units (OTU) demonstrated a unimodal trend with the increase in altitude. The non-rhizosphere bacteria diversity showed a bimodal variation trend with the rise of elevation. Bacteria diversity was in close correlation with soil nutrients, particularly in positive correlation with organic matter, total nitrogen, and available nitrogen (P<0.05) but in negative correlation with pH and available phosphorus (P>0.05). The community structures of bacteria in the forest at different elevations were highly consistent. A total of 7 159 bacterial OTUs were identified from 30 samples, which belonged to 37 phyla. The dominant bacteria phyla were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi, respectively. The response of different bacteria phyla to soil nutrients was different, and organic matter, total nitrogen, and available nitrogen were in positive correlation with Proteobacteria (P<0.05). [Conclusion] Composition and diversity of rhizosphere and non-rhizosphere soil bacteria of P. purpurea are significantly influenced by soil physical and chemical factors. The driving effects of environmental factors such as altitude and hydrothermal conditions on plants and soil are important reasons for the stable bacterial community structure. This study is expected to help gain a clearer insight into the variation of soil bacteria diversity of P. purpurea and the driving mechanism, which is expected to provide a reference for natural forest restoration in the upstream of Taohe river.