I. Data Set Descriptors A. Title: Steven C. Pennings. 2025. Marsh vegetation and soil survey at Marsh Landing, Sapelo Island GA from July 1999.. Georgia Coastal Ecosystems LTER Data Catalog (data set MSH-GCED-2511; /data/MSH-GCED-2511) B. Accession Number: MSH-GCED-2511 C. Description 1. Originator(s): Name: Steven C. Pennings Address: Department of Biology and Biochemistry University of Houston Houston, Texas 77204-5513 Country: USA Email: scpennin@central.uh.edu 2. Abstract: To document edaphic and vegetation patterns in a Georgia marsh, I sampled seven vegetation "zones" at Marsh Landing on Sapelo Island in July, 1999. Vegetation zones were delineated based on vegetation composition. I located 8 transects running from the Juncus zone in the high marsh down into the short S. alterniflora zone. The tall Spartina zone was not sampled. I sampled a single quadrat (0.25 m x 0.25 m) in each vegetation zone along each transect, for a total of 56 plots. I measured canopy height with a meter stick. I harvested aboveground biomass within each quadrat, sorted it to species, dried and weighed it. I measured soil water content gravimetrically by drying surface (4 cm deep) soil cores and expressing results as (water mass)/(mass of wet core). I determined porewater salinity by rehydrating dried soil cores with a known volume of deionized water, measuring the salinity of the supernatant after 48 h, and back-calculating to the volume of water originally present. I measured soil organic content as loss on ignition of dried soil cores at 450oC for 12 h. I measured relative elevation of each vegetation zone with a theodolite, with the elevation of the lowest zone arbitrarily set to zero. The resulting dataset describes how plant species composition, richness, height and biomass varies as a function of abiotic conditions in the upper part of a Georgia marsh. 3. Study Type: Directed Study 4. Study Themes: Marsh Ecology, Plant Ecology 5. LTER Core Areas: Primary Production 6. Georeferences: none 7. Submission Date: Nov 11, 2025 D. Keywords: biomass, canopy cover, elevation, GCE, Georgia, Georgia Coastal Ecosystems, LTER, Marsh Landing, plant biomass, Primary Production, Sapelo Island, soil organic matter, soil water content, Spartina alterniflora, species richness, USA II. Research Origin Descriptors A. Overall Project Description 1. Project Title: Georgia Coastal Ecosystems LTER Project 2. Principal Investigators: Name: James T. Hollibaugh Address: Dept. of Marine Sciences University of Georgia Athens, Georgia 30602-3636 Country: USA Email: aquadoc@uga.edu 3. Funding Period: May 01, 2000 to May 01, 2006 4. Objectives: To investigate the linkages between coastal and distant upland areas in central Georgia mediated by surface and ground water delivery to the coastal zone. This will be addressed by examining the relationship between variability in environmental factors driven by river flow, primarily salinity, and ecosystem processes and structure. 5. Abstract: We propose to establish a Long Term Ecological Research site on the central Georgia coast in the vicinity of Sapelo Island. This is a barrier island and marsh complex with the Altamaha River, one of the largest and least developed rivers on the east coast of the US, as the primary source of fresh water. The proposed study would investigate the linkages between local and distant upland areas mediated by water - surface water and ground water - delivery to the coastal zone. We would explicitly examine the relationship between variability in environmental factors driven by river flow, primarily salinity because we can measure it at high frequency, and ecosystem processes and structure. We will accomplish this by comparing estuary/marsh complexes separated from the Altamaha River by one or two lagoonal estuary/marsh complexes that damp and attenuate the river signal. This spatial gradient is analogous to the temporal trend in riverine influence expected as a result of development in the watershed. We will implement a monitoring system that documents physical and biological variables and use the time trends and spatial distributions of these variables and of their variance structure to address questions about the factors controlling distributions, trophic structure, diversity, and biogeochemistry. An existing GIS-based hydrologic model will be modified to incorporate changes in river water resulting from changes in land use patterns that can be expected as the watershed develops. This model will be linked to ecosystem models and will serve as an heuristic and management tool. Another consequence of coastal development is that as river flow decreases, groundwater flow increases and becomes nutrified. We will compare the effects of ground water discharge from the surficial aquifer in relatively pristine (Sapelo Island) versus more urbanized (mainland) sites to assess the relative importance of fresh water versus nutrients to productivity, structure and biomass turnover rate in marshes influenced by groundwater. We will also investigate the effect of marine processes (tides, storm surge) on mixing across the fresh/salt interface in the surficial aquifer. Additional physical studies will relate the morphology of salt marsh - tidal creek channel complexes to tidal current distributions and exchange. These findings will be incorporated into a physical model that will be coupled to an existing ecosystem model. The land/ocean margin ecosystem lies at the interface between two ecosystems in which distinctly different groups of decomposers control organic matter degradation. The terrestrial ecosystem is largely dominated by fungal decomposers, while bacterial decomposers dominate the marine ecosystem. Both groups are important in salt marsh-dominated ecosystems. Specific studies will examine, at the level of individual cells and hyphae, the relationship bacteria and fungi in the consortia that decompose standing dead Spartina and other marsh plants and examine how, or if, this changes along the salinity gradient. 6. Funding Source: NSF OCE 9982133 B. Sub-project Description 1. Site Description a. Geographic Location: ML -- Marsh Landing, Sapelo Island, Georgia, USA Coordinates: ML -- NW: 081 17 50.80 W, 31 25 08.03 N NE: 081 17 40.58 W, 31 25 08.03 N SE: 081 17 40.58 W, 31 24 59.03 N SW: 081 17 50.80 W, 31 24 59.03 N b. Physiographic Region: ML -- Barrier island c. Landform Components: ML -- Intertidal salt marsh d. Hydrographic Characteristics: ML -- Site borders the Duplin River and is subject to 2-3m semi-diurnal tides e. Topographic Attributes: ML -- Flat, with elevations ranging from 0-3m above mean low tide f. Geology, Lithology and Soils: ML -- unspecified g. Vegetation Communities: ML -- Spartina alterniflora in low marsh, salt pan and salt-tolerant vegetation mixture in high marsh h. History of Land Use and Disturbance: none recorded i. Climate: Climate summary for Sapelo Island, Georgia, based on NWS data from 1980-2010: Daily-aggregated Values: Mean (sample standard deviation) mean air temperature: 20.09°C (7.28°C) minimum air temperature: 15.02°C (7.96°C) maximum air temperature: 24.82°C (6.98°C) total precipitation: 3.26mm (10.3mm) Yearly-aggregated Daily Values: Mean (sample standard deviation) total precipitation (1980-2010): 1124mm (266mm) 2. Experimental or Sampling Design a. Design Characteristics: I located 8 transects running from the Juncus zone in the high marsh down into the short S. alterniflora zone. The tall Spartina zone was not sampled. b. Permanent Plots: not specified c. Data Collection Duration and Frequency: I sampled a single quadrat (0.25 m x 0.25 m) in each vegetation zone along each transect, for a total of 56 plots. Beginning of Observations: Jan 20, 1999 End of Observations: Jan 20, 1999 3. Research Methods a. Field and Laboratory Methods: Sampling -- I measured canopy height with a meter stick. I harvested aboveground biomass within each quadrat, sorted it to species, dried and weighed it. I measured soil water content gravimetrically by drying surface (4 cm deep) soil cores and expressing results as (water mass)/(mass of wet core). I determined porewater salinity by rehydrating dried soil cores with a known volume of deionized water, measuring the salinity of the supernatant after 48 h, and back-calculating to the volume of water originally present . I measured soil organic content as loss on ignition of dried soil cores at 450oC for 12 h. I measured relative elevation of each vegetation zone with a theodolite, with the elevation of the lowest zone arbitrarily set to zero. b. Protocols: none c. Instrumentation: none d. Taxonomy and Systematics: not applicable e. Speclies List: f. Permit History: not applicable 4. Project Personnel a. Personnel: Steven C. Pennings b. Affiliations: University of Houston, Houston, Texas III. Data Set Status and Accessibility A. Status 1. Latest Update: 13-Nov-2025 2. Latest Archive Date: 13-Nov-2025 3. Latest Metadata Update: 13-Nov-2025 4. Data Verification Status: Reviewed by IM B. Accessibility 1. Storage Location and Medium: Stored at GCE-LTER Data Management Office Dept. of Marine Sciences Univ. of Georgia Athens, GA 30602-3636 USA on media: electronic data download (WWW) or compact disk 2. Contact Person: Name: Wade M. Sheldon, Jr. Address: 130 Marine Sciences Marine Sciences Building Athens, Georgia 30602-3636 Country: USA Email: sheldon@uga.edu 3. Copyright Restrictions: not copyrighted 4. Restrictions: This information is licensed under a Creative Commons Attribution 4.0 International License (see: https://creativecommons.org/licenses/by/4.0/). The consumer of these data ("Data User" herein) has an ethical obligation to cite it appropriately in any publication that results from its use. The Data User should realize that these data may be actively used by others for ongoing research and that coordination may be necessary to prevent duplicate publication. The Data User is urged to contact the authors of these data if any questions about methodology or results occur. Where appropriate, the Data User is encouraged to consider collaboration or co-authorship with the authors. The Data User should realize that misinterpretation of data may occur if used out of context of the original study. While substantial efforts are made to ensure the accuracy of data and associated documentation, complete accuracy of data sets cannot be guaranteed. All data are made available "as is." The Data User should be aware, however, that data are updated periodically and it is the responsibility of the Data User to check for new versions of the data. The data authors and the repository where these data were obtained shall not be liable for damages resulting from any use or misinterpretation of the data. a. Release Date: Affiliates: Nov 11, 2025, Public: Nov 11, 2027 b. Citation: Data provided by the Georgia Coastal Ecosystems Long Term Ecological Research Project, supported by funds from NSF OCE 9982133 (data set MSH-GCED-2511) c. Disclaimer: The user assumes all responsibility for errors in judgement based on interpretation of data and analyses presented in this data set. 5. Costs: free electronic data download via WWW, distribution on CD may be subject to nominal processing and handling fee IV. Data Structural Descriptors A. Data Set File 1. File Name: MSH-GCED-2511_1_0.CSV 2. Size: 56 records 3. File Format: ASCII text (comma-separated value format) 3a. Delimiters: single comma 4. Header Information: 5 lines of ASCII text 5. Alphanumeric Attributes: 6. Quality Control Flag Codes: Q = questionable value, I = invalid value, E = estimated value 7. Authentication Procedures: 8. Calculations: Mass of water divided by mass of wet soil: (Mass of water)/(mass of wet soil) Porewater_salinity_PSU: (Salinity of supernatant) x (ml of DI water added)/(ml of water present in soil before drying) Soil_organic_content_percent: 100 x (mass of organic matter)/(mass of dry soil) 9. Processing History: Software version: GCE Data Toolbox Version 3.9.10 (23-May-2022) Data structure version: GCE Data Structure 1.1 (29-Mar-2001) Original data file processed: MSH-GCED-2511.txt (56 records) Data processing history: 13-Nov-2025: new GCE Data Structure 1.1 created ('newstruct') 13-Nov-2025: 56 rows imported from ASCII data file 'MSH-GCED-2511.txt' ('imp_ascii') 13-Nov-2025: 13 metadata fields in file header parsed ('parse_header') 13-Nov-2025: data structure validated ('gce_valid') 13-Nov-2025: Q/C flagging criteria applied, 'flags' field updated ('dataflag') 13-Nov-2025: automatically assigned study date metadata descriptors based on the range of date values in date/time columns (add_studydates) 13-Nov-2025: Name of column Plant_mass_0.0625m2 changed to Plant_mass_quadra ('ui_editor') 13-Nov-2025: updated 1 metadata fields in the Dataset section(s) ('addmeta') 13-Nov-2025: imported Dataset, Project, Site, Study, Status, Supplement metadata descriptors from the GCE Metabase ('imp_gcemetadata') 13-Nov-2025: updated 57 metadata fields in the Dataset, Project, Site, Status, Study, Supplement section(s) ('addmeta') 13-Nov-2025: updated 6 metadata fields in the Data section(s) ('addmeta') 13-Nov-2025: updated 15 metadata fields in the Status, Data sections to reflect attribute metadata ('updatecols') 13-Nov-2025: parsed and formatted metadata ('listmeta') B. Variable Information 1. Variable Name: column 1. Day column 2. Month column 3. Year column 4. Vegetation column 5. Soil_water_proportion column 6. Porewater_salinity_PSU column 7. Elevation_m column 8. Species_richness column 9. Canopy_height_cm column 10. Plant_mass_quadrat column 11. Soil_organic_content_percent 2. Variable Definition: column 1. Day of month when sampling was done column 2. Month when sampling was done column 3. Year when sampling was done column 4. Dominant vegetation type column 5. Mass of water divided by mass of wet soil column 6. Salinity of porewater column 7. Elevation of plot relative to average of lowest vegetation type column 8. Number of species in 0.25 x 0.25 m quadrat column 9. Height of canopy column 10. Dry mass of live vegetation in 0.25 x 0.25 m quadrat column 11. Organic matter as a percentage of total soil dry mass 3. Units of Measurement: column 1. D column 2. M column 3. YYYY column 4. none column 5. none column 6. PSU column 7. meters column 8. none column 9. centimeters column 10. grams column 11. % 4. Data Type a. Storage Type: column 1. integer column 2. integer column 3. integer column 4. string column 5. floating-point column 6. floating-point column 7. floating-point column 8. integer column 9. floating-point column 10. floating-point column 11. floating-point b. Variable Codes: c. Numeric Range: column 1. 20 to 20 column 2. 7 to 7 column 3. 1999 to 1999 column 4. (none) column 5. 0.16 to 0.59 column 6. 21.4 to 234.3 column 7. -0.0456 to 0.3574 column 8. 0 to 8 column 9. 4 to 80 column 10. 0 to 100.2 column 11. 0.84 to 14.18 d. Missing Value Code: 5. Data Format a. Column Type: column 1. numerical column 2. numerical column 3. numerical column 4. text column 5. numerical column 6. numerical column 7. numerical column 8. numerical column 9. numerical column 10. numerical column 11. numerical b. Number of Columns: 11 c. Decimal Places: column 1. 0 column 2. 0 column 3. 0 column 4. 0 column 5. 2 column 6. 1 column 7. 4 column 8. 0 column 9. 1 column 10. 1 column 11. 2 6. Logical Variable Type: column 1. datetime (discrete) column 2. datetime (discrete) column 3. datetime (discrete) column 4. nominal (none) column 5. calculation (continuous) column 6. calculation (continuous) column 7. data (continuous) column 8. data (discrete) column 9. data (continuous) column 10. data (continuous) column 11. calculation (continuous) 7. Flagging Criteria: column 1. x<1="I";x>31="I";x<1="Q";x>31="Q" column 2. x<1="I";x>12="I";x<1="Q";x>12="Q" column 3. none column 4. none column 5. x<0="I";x>1="I";x<0="Q";x>1="Q" column 6. x<0="I";x>300="I";x<0="Q";x>300="Q" column 7. x<-1="Q";x>1="Q" column 8. x<0="I";x>10="I";x<0="Q";x>10="Q" column 9. x<0="I";x>300="I";x<0="Q";x>300="Q" column 10. x<0="I";x>200="I";x<0="Q";x>200="Q" column 11. x<0="I";x>25="I";x<0="Q";x>25="Q" C. Data Anomalies: V. Supplemental Descriptors A. Data Acquisition 1. Data Forms: 2. Form Location: 3. Data Entry Validation: B. Quality Assurance/Quality Control Procedures: C. Supplemental Materials: D. Computer Programs: E. Archival Practices: F. Publications: not specified G. History of Data Set Usage 1. Data Request History: not specified 2. Data Set Update History: none 3. Review History: none 4. Questions and Comments from Users: none