Carbon dioxide and methane chamber flux data from temperate S. alterniflora salt-marsh

A collection of carbon dioxide (CO2), methane (CH4) gas flux and leaf area index (LAI) datasets from a temperate salt-marsh with S. alternifloria vegetation cover (39.09 ˚N, 75.44 ˚W). Measurements were collected from May 2020 through December of 2020 with 2 separate collection times per month for a total of 16 field sampling campaigns. Measurements were performed on 5 plots located within the footprint of an eddy covariance tower which collects ecosystem scale CO2 and CH4 fluxes (Ameriflux Site ID: StJ). Supporting measurements were also performed for leaf-level photosynthesis rates and plot LAI during each chamber campaign. <br> The dark and light flux chambers each occupied 1.0 m2 ground area and the vegetation stand was fully enclosed by the chambers. The sediment chambers each occupied 0.025 m2 ground area and the vegetation stand was excluded from the chambers. CO2 and CH4 fluxes from all chambers were measured with a portable greenhouse gas analyzer (LGR Los Gatos Research, Model 915-0011, San Jose, CA) for approximately 2-3 min after chamber closure. The dark and soil chambers were 100% opaque while the light chamber allowed for 90% transmission of photosynthetically active radiation. Sediment fluxes and leaf-level photosynthesis was measured from 2 points within each of the larger chamber plots. Leaf-level photosynthesis was measured with a portable photosynthesis meter (Li-6400, Licor, Lincoln, NE) and LAI was measured with a ceptometer (Accupar LP80, Meter Inc, Pullman, WA, USA). All measurements were made consecutively over the span of 2-3 hours with leaf-level measurements preformed first, followed by light chambers, dark chambers, sediment chambers and plot LAI. <br> <br>本数据集涵盖了坐标为北纬39.09°、西经75.44°的温带盐沼的相关观测数据，该盐沼植被覆盖为互花米草（S. alternifloria），包含二氧化碳（carbon dioxide, CO₂）、甲烷（methane, CH₄）气体通量与叶面积指数（leaf area index, LAI）三类数据。观测周期为2020年5月至2020年12月，每月开展2次独立采样，总计16次野外采样活动。所有观测均在涡度协方差塔（eddy covariance tower）的通量足迹范围内的5个样地内进行，该塔用于采集生态系统尺度的CO₂与CH₄通量（美国通量网Ameriflux站点编号：StJ）。每次箱式采样期间，还同步开展了叶片级光合速率与样地叶面积指数的辅助观测。<br>暗通量箱与光照通量箱的占地面积均为1.0 m²，可完全包裹植被群落；沉积物箱占地面积为0.025 m²，采样时不包含植被群落。所有箱式装置的CO₂与CH₄通量均采用便携式温室气体分析仪（LGR Los Gatos Research，型号915-0011，加利福尼亚州圣何塞市）测定，测定时长为箱室封闭后约2~3分钟。暗箱与沉积物箱为100%不透光结构，而光照箱可透过90%的光合有效辐射（photosynthetically active radiation, PAR）。沉积物通量与叶片级光合速率在每个大箱样地内的2个测点开展测定。叶片级光合速率采用便携式光合仪（Li-6400，Licor公司，内布拉斯加州林肯市）测定，叶面积指数采用冠层分析仪（Accupar LP80，Meter Inc公司，美国华盛顿州普尔曼市）测定。所有观测均在2~3小时内连续完成，测定顺序依次为：叶片级光合速率、光照通量箱、暗通量箱、沉积物箱及样地叶面积指数。<br><br>