Physical Controls On The Spatial And Temporal Biogenic Gas Dynamics In Two Subtropical Wetland Ecosystems In Florida

The spatial and temporal distribution of biogenic gas accumulation and release within peatland soils and their controls (i.e. both physical and environmental) remain highly uncertain. While several recent studies show the importance of the pore structure when defining gas dynamics, and particularly when modeling rapid gas releases (i.e. ebullition), it is unclear how different ecosystems (and particularly for subtropical systems) may show differences on such dependence. The study presented here investigates the spatial and temporal variability in biogenic gas accumulation and release in two 38-liter peat monoliths from two different wetland ecosystems in central Florida (pine flatwoods and emergent wetlands) at the laboratory scale. An array of non-invasive hydrogeophysical methods (using ground-penetrating radar, GPR) was combined with gas traps, time-lapse cameras, and direct measurements (i.e. porosity and bulk density) to explore gas content variability (i.e. build-up and release) within the peat matrix over a period of five months. The results show that specific physical soil properties for different types of wetland ecosystems play a critical role at controlling the dynamics of gas accumulation and release from peat soils. Furthermore, these differences are consistent with results on soils from other studies within similar ecosystems. This work has implications for better understanding how different types of ecosystem in subtropical systems may contribute differently to the production, accumulation, and release of greenhouse gases.泥炭地土壤中生物成因气体的聚集与释放的时空分布规律，及其调控机制（即物理与环境双重因素）目前仍存在较大不确定性。尽管近期多项研究表明，孔隙结构在阐释气体动力学特征、尤其是模拟快速气体释放（即气泡式逸出）过程中至关重要，但目前尚不清楚不同生态系统（尤其是亚热带生态系统）在这种依赖关系上存在何种差异。本研究针对佛罗里达州中部两种不同湿地生态系统（松灌平原湿地与挺水湿地）的两块38升泥炭原状土柱，在实验室尺度下探究了生物成因气体聚集与释放的时空变异性。本研究采用一系列无创水文地球物理方法（探地雷达（ground-penetrating radar, GPR）），结合气体捕集装置、定时延时相机以及直接测量手段（即孔隙度与容重），在为期5个月的观测周期内探究了泥炭基质内气体含量的变化特征（即气体聚集与释放过程）。研究结果表明，不同湿地生态系统特有的土壤物理性质，在调控泥炭土壤气体聚集与释放的动力学过程中发挥着关键作用。此外，本研究发现的这些差异，与同类生态系统中其他相关研究的土壤观测结果相一致。本研究有助于更深入理解亚热带地区不同类型生态系统在温室气体产生、聚集与释放过程中所发挥的差异化贡献。