PDF(Pubmed)
Abstract：
Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N2-fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N-cycling-related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta-diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short-term drought. Root biomass was the most important factor in driving soil bacterial community and N-cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N-cycle-related functional genes, copy numbers of ammonia-oxidizing bacteria (AOB) and autotrophic ammonia-oxidizing archaea (AOA), N2 fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N-cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N-cycling function in artificial forest ecosystems.
摘要：
落叶和常绿树木对干旱和氮（N）需求的反应不同。这些功能类型是否会影响干旱期间细菌群落在氮循环中的作用仍不确定。两种落叶树种（Alnuscremastogyne，一种固定N2的物种，和枫香）和两棵常绿树（杉木和马尾松）被用来评估控制根际土壤细菌群落和氮循环功能的因素。植物的光合速率和生物量生产，测定了根际土壤的16SrRNA测序和氮循环相关基因。门放线菌和Firmicutes的相对丰度较高，还有变形杆菌，酸杆菌,落叶乔木根际土壤中的Gemmaatimondaetes含量低于常绿。两种树木之间的细菌群落的β多样性也存在显着差异。在井水条件和短期干旱条件下，落叶树的净光合速率和生物量产量均明显高于常绿树种。根系生物量是驱动土壤细菌群落和氮循环功能的最重要因素，而不是总生物量和地上生物量。此外，响应降低的44个细菌属和46个分类单元显示沿根生物量梯度的响应增加。关于N周期相关的功能基因，氨氧化细菌（AOB）和自养氨氧化古菌（AOA）的拷贝数，N2固定基因（nifH），和反硝化基因(nirK，落叶乔木土壤中的nirS）明显高于常绿土壤。结构方程模型解释了50.2%，47.6%,48.6%,49.4%,nifH拷贝数的变异性为37.3%，AOB,AOA,nirk,和黑人，分别,根生物量对所有N循环功能基因的拷贝数都有显著的正向影响。总之,根系生物量在影响细菌群落结构和土壤氮素循环中起着关键作用。我们的发现对我们理解人工林生态系统中植物对细菌群落的控制和氮循环功能具有重要意义。
