Rhizosphere soil bacterial communities and nitrogen cycling affected by deciduous and evergreen tree species

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.

Comparative analysis of nitrogen content and its influence on actinorhizal nodule and rhizospheric microorganism diversity in three Alnus species

“…Nonmetric multidimensional scaling (NMDS) analysis also illustrated greater differences in microorganisms between the root nodules of the three alders, although the differences in potential nitrogen-fixing microorganism by the nifH gene were lower than those in actinobacteria by 16S rRNA sequencing because the formation of actinorhizal root nodules is the result of the combined action between the plant genotype, Frankia genotype and environment ( Chaia et al, 2010 ). The classification results indicated that the dominant phyla in the root nodules and rhizosphere soil of the three alders was phylum Actinomycetota, which was similar to the results for the nonleguminous species sea buckthorn ( Hippophae rhamnoides L.) and actinorhizal species A. cremastogyne ( Liu et al, 2022 ; Keyao et al, 2023 ). The biogeographic patterns and assembly process of the rhizobium communities differed in the rood nodule and the rhizosphere soil, which derived the significant differences in bacterial community composition in the root nodules and rhizosphere soils ( Jing et al, 2022 ).…”

“…These results reflected a plant’s selective ability to shape microbial communities at the classification and functional levels ( Mendes et al, 2014 ). A previous study showed that Pseudomonadota was one of the dominant phylum in A. cremastogyne monocultures and mixed plantations ( Liu et al, 2022 ). The phylum Pseudomonadota was also the dominant phyla in the root nodules of the three alders, which is similar to the findings that phylum Pseudomonadota is the main nitrogen-fixing group in the forest ecosystem ( Izquierdo and Nüsslein, 2006 ).…”

Responses of Rhizosphere and Root Surface Bacterial Communities and biomass of Cunninghamia lanceolata and Schima superba Seedlings to Nitrogen Forms

“…It has been suggested that root biomass, rather than total biomass and aboveground biomass, is the most important factor driving soil bacterial communities and nitrogen cycling functions (Liu et al 2022).…”

“…It can be seen that the negative correlation between NH 4 + -N and Acidobacteriota is not strong, especially in the SRS, but is positively correlated, and the ratios of 5:5 and 0:10 are also positively correlated. The rhizosphere of S. superba is more strongly related to the root surface and Acidobacteriota, which may be related to the N forms in the treatment, tree species and the environment of sand culture substrate (Liu et al 2022;Marschner et al 2004). In summary, under different N forms environment, there are some differences in the main dominant bacteria phyla of C. lanceolata and S. superba, which also shows the differences in rhizosphere soil bacterial communities between coniferous and broad-leaved trees (Hu et al 2021).…”