Continuous soil temperature measurements at 10 cm depth from 3 month-long deployments in summer and winter within the Georgia Coastal Ecosystems Long Term Ecological Research (GCE-LTER) site in 2017 and 2018

To understand the influence of marsh elevation and flooding on soil temperature in Spartina alterniflora marsh, we measured soil temperature at 10 cm depth along two transects that spanned a marsh edge to interior gradient. We then associated those measurements with elevation, creek water height and vegetation characteristics. Soil temperature was logged every 15 min with a Hobo Onset Tidbit Pendant Temperature probe in Spartina alterniflora-dominated marsh near the Georgia Coastal Ecosystems Long Term Ecological Research (GCE-LTER) eddy covariance flux tower. Measurements were collected along two transects of approximately 250 m in length from 18 plots (transect 1) or 20 plots (transect 2) and over 3 sample deployments of approximately 1 month in length: 27 Jul – 31 Aug 2017 (transect 1), 8 Jan – 13 Feb 2018 (transect 1) and 23 Aug – 18 Sep 2018 (transect 2). Plot elevations along each transect were measured with a Trimble R6 RTK after probes were installed in the marsh. Creek water heights were estimated with the pressure transducer associated with the GCE-LTER eddy covariance flux tower data. Spartina alterniflora height forms were measured for each sample station during August as the mean of all stem heights within 0.25 m quadrants centered over each soil probe location. While these data are 24 hr soil temperature measurements, during all three deployments, we found that daily mean soil temperature was negatively correlated with marsh elevation on the marsh platform during low tide conditions, which represented the majority of the observations.