Changes in diversity, composition and assembly processes of soil microbial communities during Robinia pseudoacacia L. restoration on the Loess Plateau, China

Abstract

Robinia pseudoacacia L. (RP) restoration has increased vegetation cover in semi-arid regions on the Loess Plateau of China, but ecological problems have also occurred due to RP restoration, such as reduced soil moisture. Further, it is still uncertain how microbial diversity, composition and assembly processes change with RP restoration in semi-arid regions. Therefore, amplicon sequencing of small subunit ribosomal ribonucleic acid (16S rRNA) and internal transcribed spacer (ITS) genes was performed to study soil bacterial and fungal diversity, composition and assembly processes at four study sites with different stand ages of RP plantations (Y10, RP plantation with stand ages less than 10 a; Y15, RP plantation with stand ages approximately 15 a; Y25, RP plantation with stand ages approximately 25 a; and Y40, RP plantation with stand ages approximately 40 a) along a 40-a chronosequence on the Loess Plateau. The diversity of soil bacteria and fungi increased significantly during the restoration period from 10 to 15 a (P<0.05). However, compared with Y15, bacterial diversity was lower at Y25 and Y40, and fungal diversity remained stable during the restoration period between 25 and 40 a. The relative abundances of Proteobacteria and Ascomycota increased during the restoration period from 10 to 15 a. Conversely, after 15 a of restoration, they both decreased, whereas the relative abundances of Actinomycetes, Acidobacteria and Basidiomycota gradually increased. The variations in soil bacterial communities were mainly related to changes in soil total nitrogen, nitrate nitrogen and moisture contents, while soil fungal communities were mainly shaped by soil organic carbon and nitrate nitrogen contents. Bacterial communities were structured by the heterogeneous selection and stochastic process, while fungal communities were structured primarily by the stochastic process. The RP restoration induced an increase in the relative importance of heterogeneous selection on bacterial communities. Overall, this study reveals the changes in microbial diversity, community composition and assembly processes with RP restoration on the Loess Plateau and provides a new perspective on the effects of vegetation restoration on soil microbial communities in semi-arid regions.

Short-Term Vegetation Restoration Enhances the Complexity of Soil Fungal Network and Decreased the Complexity of Bacterial Network

“…Previous studies have found positive [62,63] or negative [47,64] effects of vegetation restoration on fungal diversity. For example, the decrease in plant diversity in the sown treatments was followed by a decline in the diversity of plant litter and root exudates; a reduction in the heterogeneity of resources may induce a reduction in the fungal diversity [10,64].…”

“…In addition, revegetation by the sowing of a single species led to a reduction in the diversity of bacteria which was determined by a reduction in the plant diversity [10]. Thus, the different effects of vegetation restoration on the bacterial community's diversity may be determined by the soil nutrient status [71,72], restoration vegetation selection [62,69,72], plant diversity level [10,71,73], and restoration time [62,73]. Previous results found that the bacterial community's structure is closely related to the soil's nutrients in artificial vegetation restoration [69,70].…”

Differences in Juniperus przewalskii Rhizosphere Microbiomes across Age Classes: Community Diversity and Assembly

“…In this study, microbial communities in class III showed higher connectivity and complexity than those in class I and class II, indicating that the complexity of the microbial networks tended to increase with forest age ( Table 3 and Figure 3 ), which led to higher community stability [ 66 ]. This finding may be attributable to the increase in plant diversity and nutrient content availability throughout their growth cycle [ 23 ]. Wang et al [ 16 ] have revealed that the complexity of the Pinus tabulaeformis bacterial networks tended to increase markedly from 15 years to 60 years [ 16 ].…”

“…In soil ecosystems, microbial species coexist in complex arrays through positive (e.g., symbiosis) and negative (e.g., competition) associations [ 17 , 18 ], which can regulate the microbial community structure and thus adjust the functions it provides to the ecosystem [ 19 , 20 ]. Co-occurrence networks are increasingly used to infer linkages among microbial species in many different environments, including the human gut [ 21 ], oceans [ 22 ], and soils [ 23 , 24 , 25 , 26 ]. Networks analyses can be instrumental in describing network topological properties and inferring community assembly processes [ 26 ].…”

Implications of microbial community assembly for ecosystem restoration: patterns, process, and potential

“…In turn, the ratio of immigration/emigration influences community biodiversity. Differences in assembly between bacteria and fungi [59], heterotrophs and autotrophs [36], specialists and generalists [54], and abundant and rare taxa [60][61][62][63] influence community composition.…”