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.草坪草皮（Turf）由密植的草坪草植株及其下伏土壤构成，是一类受高强度人为管理的独特生态系统。土壤有机碳与氮可快速积累，并在草坪草建植后约20至50年达到平衡状态。尽管资源可利用性是影响微生物物种丰富度的重要驱动因素，但其效应会因与其他协同变化的土壤因子、以及施肥、农药施用、灌溉和修剪等反复管理措施间的复杂互作而被削弱。本研究基于建植年限分别为1、15、20及109年的草坪草皮年龄序列（turf chronosequence），通过16S与ITS扩增子测序技术，旨在探究草坪发育过程对微生物物种丰富度、群落组成，以及参与氮循环的推定功能基因丰度的影响；为更精准地开展评估，本研究同时纳入了邻近的原生松林样地。研究结果显示，资源可利用性对微生物物种丰富度的影响微弱，但对群落组成具有显著调控作用。微生物对资源可利用性及pH等其他土壤因子的响应具有类群特异性：部分菌门（如变形菌门（Proteobacteria））对土壤pH与资源可利用性无明显响应，其余菌门的相对丰度则随土壤有机碳、氮水平呈现单调变化或曲线型变化。部分菌门（如拟杆菌门（Bacteroidetes）、放线菌门（Actinobacteria）与球囊菌门（Glomeromycota））的相对丰度曲线变化规律，其生态调控机制与生态学意义仍有待进一步研究。