16S bacterial sequences from a soil community in marginal lands with or without switchgrass cultivation Metagenome

Switchgrass (SG; Panicum virgatum L.) is a perennial C4 grass native to the tallgrass prairies and a most promising feedstock in the U.S. for bioenergy production. SG has been shown to input carbon into the soil and thus has the potential to increase C sequestration. However, to fully evaluate the sustainability of SG-based biofuel production, it is crucial to understand the impacts of SG establishment on biotic/abiotic characteristics of nutrient-poor soils. Here, we aim to characterize the ecosystem-scale consequences of SG cultivation in comparison with native annual grassland fallows (FL) at two field sites (designated Sandy loam-SL and Clay loam-CL) in Oklahoma that are low in N and P nutrient availability. We hypothesize that SG sustainability relates to improvements of soil quality mediated by its influence on the soil microbial communities and the activation of beneficial plant-microbe interactions. This will ultimately result in measurable effects on key ecosystem functions like C sequestration and greenhouse gas (GHG) mitigation. During the first two growing seasons, these four plots were monitored monthly. We measured topsoil chemistry, GHG fluxes (CO2 and CH4), and characterized microbial communities using 16S rRNA high-throughput sequencing. GHG concentrations were measured using cavity ring-down spectrometry (i.e. Picarro G2508 analyzer).

柳枝稷（Switchgrass, SG; *Panicum virgatum L.*）是原产于高草草原的多年生C4草本植物，亦是美国极具应用前景的生物能源原料。研究表明，柳枝稷可向土壤输入碳，因此具备提升碳固存（C sequestration）能力的潜力。然而，若要全面评估柳枝稷基生物燃料生产的可持续性，明晰柳枝稷定植对养分贫瘠土壤的生物/非生物特性的影响至关重要。本研究选取美国俄克拉荷马州两处氮、磷养分水平均较低的野外样地（分别命名为砂壤土-SL与黏壤土-CL），以原生一年生草地撂荒地（FL）为对照，旨在表征柳枝稷种植相较于撂荒地的生态系统尺度效应。我们提出研究假说：柳枝稷的可持续性与其通过调控土壤微生物群落、激活有益植物-微生物互作来改善土壤质量的作用密切相关，这最终将对碳固存、温室气体（Greenhouse Gas, GHG）减排等核心生态系统功能产生可量化的影响。在首个两个生长季内，我们对这四块样地开展了月度监测，测定了表层土壤化学性质、温室气体通量（CO₂与CH₄），并通过16S rRNA高通量测序对微生物群落进行了表征。温室气体浓度采用腔环衰荡光谱法（即Picarro G2508分析仪）进行测定。