Land use effects on soil protists and their top-down regulation on bacteria and fungi in soil profiles

Soil protists play an essential role in shaping microbial community structure and soil nutrient cycling. However, our understanding of land use effects on soil protists and their functions in the microbial food web in soil profiles is still limited. This study is designed to i) compare the community distributions of soil protists along soil depths in different land uses (forest vs vineyard agricultural), and ii) investigate the role of protists in microbial top -down regulation on bacteria and fungi. Soils were sampled in native forest and vineyard agricultural ecosys-tems in the Hunter Valley, New South Wales, Australia at depths: 5-15 cm, 45-55 cm, and 90-100 cm. We found that: 1) different protist community structures were observed between topsoils and subsoils, and the influence of land use decreased with depth; 2) protists community was largely driven by soil properties, i.e., soil pH and soil organic carbon; 3) protists functioning as consumers constitute the largest part of soil protists community (e.g., >75 % in topsoils), which regulated bacterial and fungal community diversity. This study presents the varying distribution patterns of soil protists in soil profiles from different land uses and highlights the importance of soil protists on microbial community regulation. Manipulation of the soil protist community may influence microbial functions in soils.