4.3 Predominant factors governing bacterial, fungal, and protist communities
Soil C, N, and P were strongly linked to Proteobacteria, Acidobacteria, Ascomycota, and Cercozoa (Fig. 5). Nutrient cycling‒related Proteobacteria and Acidobacteria are copiotrophic and oligotrophic, respectively, and are sensitive to changes in nutrient levels (Ai et al., 2015; Fierer et al., 2007). Increasing soil C and N availability stimulates Proteobacteria growth whereas Acidobacteria prefer to live under nutrient-poor conditions (Ai et al., 2015; Dai et al., 2018; Fierer et al., 2012). Ascomycota are free-living saprotrophic fungi that are involved in organic matter decomposition and regulate resource availability (Baldrian et al., 2011; Chen et al., 2021). Here, Proteobacteria, Acidobacteria, Ascomycota, and Cercozoa were the dominant taxa and played important roles in modulating the soil C, N, and P nutrient content.
In this study, temperature, vegetation type, and soil properties markedly influenced the composition of bacterial, fungal, and protist communities. Temperature was the key climate factor affecting bacterial and fungal community composition. Bacterial and fungal activity increased with soil temperature in the range of 5–30 °C (BÁRcenas-Moreno et al., 2009; Pettersson and Bååth, 2003; Pietikainen et al., 2005). The increased in soil temperature improved the growth of certain bacterial and fungal taxa, thereby altering bacterial and fungal community composition. Fungi, such as mycorrhizal fungi form beneficial mutualistic association with the roots of their plant host (Johnson et al., 2004; Smith and Read, 2010). Compared with bacterial community composition, fungal community composition was more strongly affected by vegetation type. However, protist community composition was more sensitive to vegetation type and soil physicochemistry than it was to soil temperature. These discoveries confirm those of previous studies reporting that differences in precipitation rate and water availability rather than changes in soil temperature were limiting factors influencing protist abundance (Stefan et al., 2014). Taken together, temperature and vegetation were the primary factors for predicting the changes in bacterial and fungal community composition, while vegetation and soil property are the main determinants of protist taxa.