AIMS Talladega Greenhouse Gas Data (AIMS_SE_TAL_GHGS)

This resource specifically includes the greenhouse gas (GHGS) seasonal (approach 2) and synoptic (approach 3) sample datasets collected in our Talladega research watershed, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Approach 2 and approach 3 sampling campaigns conducted in Talladega research watershed were designed in support of the sampling goals of the NSF funded Aquatic Intermittency effects on Microbiomes in Streams (AIMS) project (EPSCoR funded project, OIA 2019603). Specifically, the MIMS dissolved gas data was collected by the biogeochemistry team to better understand the effects of stream drying on dissolved gases in the southeastern US. The Talladega National Forest (Cleburne County, AL, USA; Watershed Outlet Lat/Long: 33.76219799, -85.59550775) contains a non-perennial unnamed tributary of Pendergrass Creek, where our study sites were located, as well as 0.92 km^2 of mixed coniferous and deciduous forest in the Piedmont Upland physiographic section. The research watershed also spans an elevation range from 345 to 456 m above sea level and is a tributary to the Coosa River (within the larger Mobile-Tombigbee basin). The region has a humid subtropical climate, with mean daily January and July air temperatures of 5.3°C and 25.3°C respectively, and mean annual precipitation of 1,400 mm/yr.

On six different occasions from June 29, 2022 to January 29, 2024, we collected dissolved gas (GHGS) samples seasonally across 7 sampling locations (approach 2). On one separate occasion during June 2022, we collected GHGS samples from 49 sampling locations (approach 3) within the same Talladega research watershed. For the approach 3 sampling campaign, the sites were selected to balance multiple competing priorities: (i) strategically targeting existing monitoring infrastructure with long-term data; (ii) including sites near several known springs and tributary junctions; and (iii) including a range of drainage area and topographic wetness index (TWI) values, both of which have been correlated with flow permanence. Briefly, the sites selected based on drainage area and TWI were chosen by binning drainage area into 10 bins and then binning TWI into quintiles within each drainage area bin. We then randomly selected a point in each bin after accounting for points selected based on existing infrastructure, springs, and tributaries, as well as enforcing a minimum spacing of 100 m between locations. We then made minor adjustments to points to account for field conditions, for instance adjusting locations with respect to a road crossing.

Included in the Content section is the sampling datasheet that was used during field collection, as well as one compiled excel file containing approach 2 and 3 GHGS TAL data. Within the compiled excel file, the 'Working Files' tab contains the processed GHGS data before taking averages of all the replicates. The 'Final Data' tab has the data that should be used for analyses with the averages of all 3 replicates and standard deviations (sd) in uM units. Also, there are columns regarding whether the sample was from approach 2 or 3. Approach 1 samples were any MIMS samples collected at Talladega watershed outlet site (TLMO1) during approach 2 or 3 sampling campaigns.

本数据集专属收录了塔拉迪加研究流域内采集的温室气体（Greenhouse Gas, GHGS）季节采样（方法2）与天气尺度采样（方法3）样本数据集，涵盖二氧化碳（Carbon Dioxide, CO₂）、甲烷（Methane, CH₄）及一氧化二氮（Nitrous Oxide, N₂O）。塔拉迪加研究流域内开展的方法2与方法3采样工作，均为支撑美国国家科学基金会（National Science Foundation, NSF）资助的“溪流间歇特性对微生物组的影响（Aquatic Intermittency effects on Microbiomes in Streams, AIMS）”项目的采样目标而设计（该项目为EPSCoR资助项目，项目编号OIA 2019603）。具体而言，生物地球化学团队采集了膜进样质谱（Membrane Inlet Mass Spectrometry, MIMS）溶解气体数据，以深入解析美国东南部溪流干涸过程对水体溶解气体的影响。塔拉迪加国家森林（位于美国阿拉巴马州克莱本县；流域出口经纬度：33.76219799, -85.59550775）内分布有彭德格拉斯溪的一条季节性无名支流，本研究采样点位即布设于此；同时该流域涵盖皮德蒙特高地地貌区的0.92平方千米针阔混交林。本研究流域海拔范围为345至456米（以海平面为基准），同时作为库萨河的支流隶属于更大的莫比尔-通比格比流域。该区域属亚热带湿润气候，1月与7月的日均气温分别为5.3℃与25.3℃，年平均降水量达1400毫米/年。

2022年6月29日至2024年1月29日期间，我们共计开展6次野外采样工作，通过方法2在7个采样点位完成季节性溶解气体（GHGS）样本采集。2022年6月另有1次独立采样工作，通过方法3在同一塔拉迪加研究流域内的49个采样点位完成GHGS样本采集。针对方法3采样工作，点位遴选需兼顾多项存在竞争关系的优先级目标：（1）优先覆盖已积累长期监测数据的现有监测基础设施；（2）纳入多处已知泉点及支流汇口附近的采样点位；（3）涵盖一系列汇水面积与地形湿度指数（Topographic Wetness Index, TWI）区间，上述两项指标均与河道径流持久性存在显著相关性。简言之，基于汇水面积与地形湿度指数遴选点位时，首先将汇水面积划分为10个区间，再在每个汇水面积区间内将地形湿度指数划分为5个分位数区间。在扣除基于现有监测设施、泉点及支流已遴选的点位后，我们在每个区间内随机选取采样点位，并强制要求点位间最小间距不低于100米。随后我们针对实地勘测条件对部分点位进行微调，例如调整跨道路采样点的位置。

本数据集内容包含野外采样时使用的采样记录表，以及1份整合了方法2与方法3的GHGS TAL数据的Excel文件。在整合后的Excel文件中，"Working Files"工作表包含所有重复样本取平均前的预处理GHGS数据；"Final Data"工作表包含可供分析使用的最终数据，其中包含3次重复样本的平均值及以微摩尔（uM）为单位的标准差。此外，表格中设有标注样本所属采样方法（方法2或方法3）的列。方法1样本指在方法2或方法3采样工作期间，于塔拉迪加流域出口点位（TLMO1）采集的所有MIMS样本。