The soil microbial community of turf: structural and functional evolutions over time

Turf, consisting of closely-spaced turfgrass plants and the subtending soil, is a unique ecosystem subject to intense management. And yet, soil organic C and N can be accumulated quickly and reach an equilibrium about 20 to 50 years after turfgrass establishment. While resource availability is an important driver for microbial species richness, its effects can be lessened due to complex interactions with co-varied other edaphic factors and repeated management events, such as fertilization, pesticide use, irrigation and mowing. In this work, we aimed to examine the impacts of turf development on microbial species richness, community composition, and the abundances of putative functional genes involved in N cycle from a turf chronosequence (i.e., 1, 15, 20, and 109 years old) through 16S and ITS amplicon sequencing. Adjacent native pine was also included for a better evaluation. Our results showed that resource availability influenced little on microbial species richness and yet significantly on community composition. Microbial responses to resource availability and other edaphic factors, such as pH were taxonomically specific. While some phyla showed no response to soil pH and resource availability, such as Proteobacteria, others showed either monotonically or curvilinear change with soil organic C and N status. The curvilinear function of relative abundances for some phyla, e.g., Bacteroidetes, Actinobacteria, and Glomeromycota, needs to be investigated further in terms of ecological controls and significance.