This resource specifically includes the Membrane Inlet Mass Spectrometer (MIMS) dissolved gas seasonal (approach 2) and synoptic (approach 3) sample datasets collected in our Talladega research watershed, including Argon (Ar), Oxygen (O2), Nitrogen (N2), N2:Ar ratio, and O2:Ar ratio. 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 March 29, 2022 to January 29, 2024, we collected dissolved gas (MIMS) samples seasonally across 7 sampling locations (approach 2). On one separate occasion during June 2022, we collected MIMS 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 MIMS TAL data. Within the compiled excel file, the 'Working Files' tab contains the processed MIMS 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. The raw MIMS data was processed and calculated via the package 'MIMSY' (R Package; M. Kelly (2020), https://cran.r-project.org/package=mimsy) and has 3 data points per replicate.