Changes in bacterial community composition across natural grassland and pine forests in the Bunya Mountains in subtropical Australia

Abstract

Tree and grass species coexist in many ecosystems worldwide and support multiple ecosystem functions and services. However, the distribution of bacterial communities and factors driving coexistence in tree–grass associations and their ecosystem functions remain poorly understood. In this study, the distribution of soil bacteria and their link to changes in abiotic factors were investigated in adjacent montane grassland (C4 plants) and pine forest (bunya pine and hoop pine; C3 plants) sites in the Bunya Mountains, subtropical Australia. Different vegetation (grassy balds and forest) had a substantial effect on terrestrial ecosystem properties, with higher levels of soil nutrients (e.g. total nitrogen (N), total phosphorus (P)) and electrical conductivity (EC), and lower δ13C values and pH under forests compared with grassland. Bacterial α-diversity (total species per operational taxonomic unit richness) did not differ between grassland and pine forest sites, whereas strong shifts in the bacterial community composition and structure were evident. Patterns in bacterial community structure were strongly associated with changes in soil pH, EC, total P and δ13C. Different bacterial groups associated with pine forest (Gammaproteobacteria and Alphaproteobacteria) and grassland (Acidobacteria and Verrucomicrobia) were identified as key groups contributing to the segregation of these two ecosystems in the Bunya Mountains. These findings suggest that heterogeneity in soil edaphic properties (e.g. key nutrients) likely contributed to variation in bacterial β-diversity of grassland and pine forest, which has potential implications for species coexistence and ecosystem function in montane eastern Australia.

Soil properties and microbiome of annual and perennial cultivated grasslands on theQinghai–TibetanPlateau

“…At the genus level, soil properties explained approximately 78% of soil bacteria variation (Figure 5a), concurring with Yang et al (2018). Among these soil properties, N tot , SOC, and , were the dominant factors influencing soil bacterial community composition (Table 3), similar to reports of many other studies (Gömöryová et al, 2009; Li et al, 2020; Shen et al, 2019). This is because the quantity and quality of external inputs are important drivers of soil bacterial activity and structure and affect substrates on which the bacteria depend (Huang et al, 2017; Rodrigues et al, 2013).…”

“…Changes in soil pH influence resource acquisition and utilization (Cheng et al, 2021) and membrane‐bound proton pumps and protein stability; thus, soil pH constrains microbial physiological activity by limiting the survival rate of individual taxa (Booth, 1985; Zhou et al, 2020). It has been reported that soil pH is an important factor affecting soil bacterial communities (e.g., Hu et al, 2019; Shen et al, 2019; Zhou et al, 2017) as found in the present study (Table 3).…”

Soil organic matter and geochemical characteristics shape microbial community composition and structure across different land uses in an Australian wet tropical catchment

“…Actinobacteria are considered to play an important role in decomposition of organic materials, particularly for degradation of macromolecules such as cellulose, hemicellulose, lignin and chitin (Steger et al, 2007) and mostly benefit from the availability of a rich substrate with high C sources (Shen et al, 2019).…”

“…In this study, a significant shift in soil microbial community occurred across land uses through compositional and structural changes of discrete bacterial and fungal groups (Figures 3 and 6). Such variations were attributed to multiple mechanisms such as the impact of vegetation type and management practices on nutrient, energy flow and heterogeneity of soil physicochemical conditions across land uses (Figure 5) (Lauber et al, 2008; Shen et al, 2019; Subrahmanyam et al, 2021). Generally, SOM characteristics were more influential on structuring soil microbial community across land uses compared with soil geochemical characteristics, while the shift in soil bacterial community was more strongly correlated to variability of soil geochemical and organic matter characteristics compared with fungi (Figure 7).…”

“…For example, the relative abundance of Actinobacteria, as the second most dominant group of bacteria in soils, was significantly correlated with TOC:TN ratios. Actinobacteria are considered to play an important role in decomposition of organic materials, particularly for degradation of macromolecules such as cellulose, hemicellulose, lignin and chitin (Steger et al, 2007) and mostly benefit from the availability of a rich substrate with high C sources (Shen et al, 2019).…”