Microbial community structure and functions differ between native and novel (exotic-dominated) grassland ecosystems in an 8-year experiment

Abstract

Aims Grasslands dominated by non-native (exotic) species have replaced purely native-dominated areas in many parts of the world forming 'novel' ecosystems. Altered precipitation patterns are predicted to exacerbate this trend. It is still poorly understood how soil microbial communities and their functions differ between high diversity native-and low diversity exotic-dominated sites and how altered precipitation will impact this difference. Methods We sampled 64 experimental grassland plots in central Texas with plant species mixtures of either all native or all exotic species; half with summer irrigation. We tested how native vs. exotic plant species mixtures and summer irrigation affected bacterial and fungal community composition and structure, the influence of niche vs. neutral processes for microbial phylotype cooccurrence (C-score analysis), and rates of phosphorus and nitrogen mineralization across an 8-year experiment. Results Native and exotic-dominated plots had significantly different fungal community composition and structure, but not diversity, throughout the length of the study, while changes in bacterial communities were limited to certain wet and cool years. Nitrogen and phosphorus mineralization rates were higher under native plant mixtures and correlated with the abundance of particular fungal species. Microbial communities were more structured in exotic than native grassland plots, especially for the fungal community. Conclusions The results indicate that conversion of native to exotic C 4 dominated grasslands will more strongly impact fungal than bacterial community structure. Furthermore, these impacts can alter ecosystem functioning belowground via changes in nitrogen and phosphorus cycling.

Soil depth and grassland origin cooperatively shape microbial community co‐occurrence and function

“…As we found previously (Checinska‐Sielaff et al. ), fungal communities were more strongly impacted by the plant community treatment than bacterial communities, demonstrating that novel grassland ecosystems have altered soil fungal communities compared with the native grasslands that they replaced. Although irrigation did not alter the composition of detected microbes (active, dormant, relic), the interactions among community members responded to irrigation.…”

“…Native and exotic communities differed in fungal community composition in the upper soil layer (up to 10 cm) over eight years in a previous study at this site (Checinska‐Sielaff et al. ). However, this is the first study to show that conversion from native to exotic plant species has impacts well beyond the surface soil.…”

Effects of plant community history, soil legacy and plant diversity on soil microbial communities

“…In terms of bacterial and fungal community composition, our samples tended to cluster along a plant species richness gradient from monocultures to 60 species‐mixtures (Figure 1), indicating that plant diversity led to ‘directed’ microbial species turnover, as has been found in previous biodiversity experiments (Grüter et al., 2006; LeBlanc et al., 2015; Schlatter et al., 2015). However, another study with bulk soil from a grassland ecosystem in Texas found that fungal community composition was not influenced by plant diversity but rather by the addition of a single exotic plant species (Checinska Sielaff et al., 2018). Overall, these studies suggest bulk soil microbial communities are less strongly influenced by plant species richness than rhizosphere microbial communities.…”

Effects of plant community history, soil legacy and plant diversity on soil microbial communities

“…1), indicating that plant diversity led to “directed” microbial species turnover, as has been found in previous biodiversity experiments (Grüter et al, 2006; LeBlanc et al, 2015; Schlatter et al, 2015). However, another study with bulk soil from a grassland ecosystem in Texas found that fungal community composition was not influenced by plant diversity but rather by the addition of a single exotic plant species (Checinska Sielaff et al, 2018). Overall, these studies suggest bulk soil microbial communities are less strongly influenced by plant species richness than rhizosphere microbial communities.…”