Effects of Spartina alterniflora Invasion on Soil Microbial Community Structure and Ecological Functions

Abstract

It has been reported that the invasion of Spartina alterniflora changed the soil microbial community in the mangrove ecosystem in China, especially the bacterial community, although the response of soil fungal communities and soil microbial ecological functions to the invasion of Spartina alterniflora remains unclear. In this study, we selected three different communities (i.e., Spartina alterniflora community (SC), Spartina alterniflora-mangrove mixed community (TC), and mangrove community (MC)) in the Zhangjiangkou Mangrove Nature Reserve in China. High-throughput sequencing technology was used to analyze the impact of Spartina alterniflora invasion on mangrove soil microbial communities. Our results indicate that the invasion of Spartina alterniflora does not cause significant changes in microbial diversity, but it can alter the community structure of soil bacteria. The results of the LEfSe (LDA Effect Size) analysis show that the relative abundance of some bacterial taxa is not significantly different between the MC and SC communities, but different changes have occurred during the invasion process (i.e., TC community). Different from the results of the bacterial community, the invasion of Spartina alterniflora only cause a significant increase in few fungal taxa during the invasion process, and these taxa are at some lower levels (such as family, genus, and species) and classified into the phylum Ascomycota. Although the invasion of Spartina alterniflora changes the taxa with certain ecological functions, it may not change the potential ecological functions of soil microorganisms (i.e., the potential metabolic pathways of bacteria, nutritional patterns, and fungal associations). In general, the invasion of Spartina alterniflora changes the community structure of soil microorganisms, but it may not affect the potential ecological functions of soil microorganisms.

Keywords: Spartina alterniflora invasion; community structure; ecological functions; funguild analysis; high throughput sequencing; mangrove; soil microbial; tax4fun analysis.

Figure 1

The relative abundance of bacteria (a) and fungi (b) phylum (% of the total number of reads) in the Spartina alterniflora community (SC), Spartina alterniflora–mangrove mixed community (TC), and the mangrove community (MC) samples, where 1 represents the 0–15 cm soil layer and 2 represents the 15–30 cm soil layer.

Figure 2

LEfSe analysis showing the significant differences at different bacterial taxonomic levels among SC, TC, and MC communities in 0–15 cm soil layer (a,c,e) and 15–30 cm soil layer (b,d,f). The colors of red, green, and yellow correspond to the SC, TC, and MC communities, respectively. Abbreviation: p—phylum; c—class; o—order; f—family; and g—genus.

Figure 3

LEfSe analysis showing the significant differences at different fungal taxonomic levels among SC, TC, and MC communities in 0–15 cm soil layer (a,b,d) and 15–30 cm soil layer (c,e). The colors of red, green, and yellow correspond to the SC, TC, and MC communities, respectively. Abbreviation: p—phylum; c—class; o—order; f—family; g—genus; Phia_dimor—Phialemonium_dimorphosporum; and Spo_sp_1_CMW9492—Sporothrix_sp_1_CMW9492.

Figure 4

Venn diagram showing the unique and shared OTUs among the SC, TC, and MC samples in soil layer 0–15 cm (a,c) and 15–30 cm (b,d) in bacterial (a,b) and fungal (c,d) communities.

Figure 5

Results of PCoA showing the first two principal coordinates that combined explain 46.26% and 35.48% of the observed variation in bacterial (a) and fungal (b) community. The shapes of up triangle and square on the figure legend correspond to the soil layer of 0–15 cm and 15–30 cm, and the colors of red, green, and yellow correspond to the SC, TC, and MC communities, respectively. The ellipsoids corresponds to the differences among plant communities (PerMANOVA test, p < 0.05).