Understory Dwarf Bamboo Affects Microbial Community Structures and Soil Properties in a Betula ermanii Forest in Northern Japan

Abstract

In order to understand the relationships between understory bamboo and soil properties, we compared microbial community structures in the soil of a Betula ermanii boreal forest with Sasa kurilensis present and removed using high-throughput DNA sequencing. The presence of understory S. kurilensis strongly affected soil properties, including total carbon, total nitrogen, nitrate, and the C:N ratio as well as relative soil moisture. Marked differences were also noted in fungal and bacterial communities between plots. The relative abundance of the fungal phylum Ascomycota was 13.9% in the Sasa-intact plot and only 0.54% in the Sasa-removed plot. Among the Ascomycota fungi identified, the most prevalent were members of the family Pezizaceae. We found that the abundance of Pezizaceae, known to act as mycorrhizal fungi, was related to the amount of total carbon in the Sasa-intact plot. The relative abundance of Proteobacteria was significantly higher, whereas those of Planctomycetes and Actinobacteria were lower in the Sasa-intact plot than in the Sasa-removed plot. Furthermore, the results obtained suggest that some species of the phylum Planctomycetes are more likely to occur in the presence of S. kurilensis. Collectively, these results indicate that the presence of S. kurilensis affects microbial communities and soil properties in a B. ermanii boreal forest.

Keywords: Sasa kurilensis; bacteria; boreal forest; fungi; high-throughput sequencing.

Fig. 1

Locations of three sampling circles used in both study plots (Sasa-intact and Sasa-removed).

Fig. 2

Monthly mean (A) soil moisture (squares) and (B) temperature (circles) of three sampling circles in Sasa-intact (filled) and Sasa-removed (open) plots between July 2014 and June 2015. T1: air temperature; T2: soil surface temperature; T3: 15-cm-deep soil temperature.

Fig. 3

Differences in soil physicochemical properties between Sasa-intact (gray) and Sasa-removed (white) plots according to a generalized linear mixed model. The superscript asterisk indicates significance at p<0.05. The response variable was the concentration of soil properties, the fixed effect was the two study plots, and the random effect was the five sampling dates. Mean values with different letters denote significant differences among the pooled data (i.e., data for five sampling dates for both plots) (p<0.05; Tukey’s HSD, n=9). TN: total nitrogen; TC: total carbon; NH₄-N: ammonium; NO₃-N: nitrate. Vertical lines indicate standard errors.

Fig. 4

Rarefaction curves for microbial OTUs in the three circles on five sampling dates, with clustering at a 97% rRNA sequence similarity. Solid and dashed lines represent the OTUs of the bacterial and fungal communities, respectively.

Fig. 5

Differences in the relative abundance of soil microbial communities in Sasa-intact and Sasa-removed plots for five sampling dates according to a Kruskal–Wallis test. The asterisk indicates significance (p<0.05; n=15). (A) Bacterial phyla; (B) Fungal phyla; (C) Fungal classes.

Fig. 6

Redundancy analysis of main (A) bacterial and (B) fungal communities in Sasa-intact (solid circles) and Sasa-removed (open circles) plots based on Canoco 4.5. The purple, light green, orange, aqua, and pink colors represent the sampling dates of 23 July 2014, 1 October 2014, 3 June 2015, 4 August 2015, and 1 October 2015, respectively. Blue and dark green arrows indicate the abundance of microbes and values of soil properties, respectively. TN: total nitrogen; TC: total carbon; NH₄-N: ammonium; NO₃-N: nitrate.