Static chamber fluxes of carbon dioxide and methane from coastal wetlands on Upper Cape Cod, Massachusetts and supporting environmental data, 2021

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
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  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
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  2. How were the data generated, processed, and modified?
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What does this data set describe?

1. How might this data set be cited?
   Sanders-DeMott, Rebecca, Eagle, Meagan J., Kroeger, Kevin D., Brooks, Thomas W., Jennifer A. O'Keefe Suttles, Nick, Sydney K., Mann, Adrian G., Kuhl, Sophie, and Gibson, Simone, 2022, Static chamber fluxes of carbon dioxide and methane from coastal wetlands on Upper Cape Cod, Massachusetts and supporting environmental data, 2021: data release DOI:10.5066/P9RRL3T0, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • https://doi.org/10.5066/P9RRL3T0
   • https://www.sciencebase.gov/catalog/item/629fa3e2d34ec53d276fd537

   This is part of the following larger work.
   Sanders-DeMott, Rebecca, Eagle, Meagan, Kroeger, Kevin, Wang, Faming, Brooks, T. Wallace, Jennifer A. O'Keefe Suttles, Nick, Sydney, Mann, Adrian, and Tang, Jianwu, 2022, Carbon dioxide and methane fluxes with supporting environmental data from coastal wetlands across Cape Cod, Massachusetts (ver 2.0, June 2022): data release DOI:10.5066/P9RRL3T0, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.5066/P9RRL3T0
   • https://www.sciencebase.gov/catalog/item/62557ae8d34e21f8276f4879

   Other_Citation_Details:

   Suggested citation: Sanders-DeMott, R., Eagle, M.J., Kroeger, K.D., Wang, F., Brooks, T.W., O'Keefe Suttles, J.A., Nick, S.K., Mann, A.G., and Tang, J. 2022, Carbon dioxide and methane fluxes with supporting environmental data from coastal wetlands across Cape Cod, Massachusetts (ver 2.0, June 2022): U.S. Geological Survey data release, https://doi.org/10.5066/P9RRL3T0.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -70.6703
   East_Bounding_Coordinate: -70.4984
   North_Bounding_Coordinate: 41.6015
   South_Bounding_Coordinate: 41.5295
   

3. What does it look like?

   https://www.sciencebase.gov/catalog/file/get/629fa3e2d34ec53d276fd537?name=phragmites_chamber.jpg&allowOpen=true (JPEG)

   Browse graphic is a photograph of a chamber sampling platform in a Phragmites wetland at Sage Lot Pond, Waquoit, MA.

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 25-Apr-2021

   Ending_Date: 18-May-2022

   Currentness_Reference:

   Ground condition. These dates bracket the period of monthly sampling when the measurements were made.

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: tabular digital data
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      

      Indirect_Spatial_Reference:

      Geographic Names Information System (GNIS) placenames are included as keywords to give the general location of core collections. The entity contains attributes with specific latitude and longitude of each core collection; several attributes are also included to describe the core collection location (nearest body of water and vegetation type). Refer to the entity and attribute definitions for "site_name", "veg_type", "site_name", "status", and "sampling_location_name" for details.

      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point
   2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 1.0E-5. Longitudes are given to the nearest 1.0E-5. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
      

7. How does the data set describe geographic features?

   chamber_fluxes_2021.csv

   Comma Separated Value (CSV) file containing data on methane and carbon dioxide fluxes. This dataset has 216 records. (Source: Producer Defined)

   date

   Date the measurement was collected in the format yyyy-mm-dd. (Source: Producer Defined) Numeric value representing the date

   start_datetime

   Date and time that the chamber incubation was started in local standard time (UTC - 05:00) in the format yyyy-mm-dd hh:mm:ss. (Source: Producer Defined) Numeric value representing the date and time.

   end_datetime

   Date and time that the chamber incubation was ended in local standard time (UTC - 05:00) in the format yyyy-mm-dd hh:mm:ss. (Source: Producer Defined) Numeric value representing the date and time.

   site_name

   Site name of sampling location (Source: Producer Defined)

   Value	Definition
   Sage Lot Pond	A site located within the Waquoit Bay National Estuarine Research Reserve in Waquoit, MA.
   Flat Pond	A site located within the Waquoit Bay National Estuarine Research Reserve in Waquoit, MA.
   Woods Hole Park	A site located in the village of Woods Hole, MA.
   Quaker Meeting House	A site located within West Falmouth, MA.

   status

   Hydrological management status of the sampling location (Source: Producer Defined)

   Value	Definition
   Unrestricted	Indicates that the sampling location experiences natural, unrestricted tidal exchange.
   Impounded	Indicates that at this sampling location water is retained but tidal exchange is limited or excluded by infrastructure such as dikes, roads, or culverts.

   veg_type

   Dominant vegetation at sampling location (Source: Producer Defined)

   Value	Definition
   Phragmites Wetland	Sampling location is a wetland dominated by Phragmites australis
   Typha/Schoenoplectus Wetland	Sampling location is a wetland dominated by Typha latifolia and Schoenoplectus

   sampling_location_name

   Sampling location name indicating both the hydrological management and salinity status relative to the geographical site as referenced in the related publication (Sanders-DeMott and others, 2022) (Source: Producer Defined)

   Value	Definition
   Unrestricted-High	Sampling location that experiences natural, unrestricted tidal exchange and is the high salinity plot of the site pair at Sage Lot Pond as referenced in the related publication (Sanders-DeMott and others, 2022)
   Unrestricted-Low	Sampling location that experiences natural, unrestricted tidal exchange and is the low salinity plot of the site pair at Sage Lot Pond as referenced in the related publication (Sanders-DeMott and others, 2022)
   Impounded-FPP	Sampling location that experiences tidal exchange that is limited or excluded and is located in a Phrgamites stand at Flat Pond
   Impounded-FPTS	Sampling location that experiences tidal exchange that is limited or excluded and is located in a mixed Typha latifolia and Schoenoplectus stand at Great Flat Pond
   Impounded-WH	Sampling location that experiences tidal exchange that is limited or excluded and is located in Woods Hole Park in Woods Hole, MA
   Impounded-QMH	Sampling location that experiences tidal exchange that is limited or excluded and is located on Quaker Meeting House property in West Falmouth, MA

   chamber_rep

   Identifier of the chamber replicate at each sampling location (Source: Producer Defined)

   Range of values
   Minimum:	1
   Maximum:	3

   latitude

   Latitude decimal degrees north, NAD83 (Source: Producer Defined)

   Range of values
   Minimum:	41.52952
   Maximum:	41.60149
   Units:	decimal degrees

   longitude

   Longitude decimal degrees west, NAD83. The negative value indicates a location in the western hemisphere. (Source: Producer Defined)

   Range of values
   Minimum:	-70.67031
   Maximum:	-70.49842
   Units:	decimal degrees

   elevation

   Elevation relative to NAVD88 datum in meters. (Source: Producer Defined)

   Range of values
   Minimum:	0.15
   Maximum:	1.36
   Units:	meters

   chamber_transparency

   Indicator of whether chamber incubation was conducted with transparent chamber to allow light exposure or opaque chamber to block out light. (Source: Producer Defined)

   Value	Definition
   opaque	Chamber incubation conducted with an opaque cover to block out sunlight and assess fluxes in the dark.
   transparent	Chamber incubation conducted with a transparent chamber to allow sunlight and assess fluxes in the light.

   CH4_flux

   Flux of methane calculated from the slope of CH4 concentration change in nanomoles of CH4 per square meter per second (nmol CH4 m-2 sec-1). Positive values indicate a flux of methane out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. (Source: Producer Defined)

   Range of values
   Minimum:	0.38
   Maximum:	587.62
   Units:	nmol CH4 m-2 sec-1

   CH4_flux_ebullition

   Flux of methane calculated in nanomoles of CH4 per square meter per second (nmol CH4 m-2 sec-1) when ebullition was suspected. Calculation is based on the difference between initial and final concentration as applicable when ebullition was suspected due to non-linear changes in CH4 concentration during incubation. Positive values indicate a flux of methane out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. (Source: Producer Defined)

   Value	Definition
   empty cell	No ebullition was observed

   Range of values
   Minimum:	49.16
   Maximum:	344.48
   Units:	nmol CH4 m-2 sec-1

   CO2_flux

   Flux of carbon dioxide calculated from the slope of CO2 concentration change in micromoles of CO2 per square meter per second (umol CO2 m-2 sec-1). Positive values indicate a flux of CO2 out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. (Source: Producer Defined)

   Range of values
   Minimum:	-24.92
   Maximum:	21.29
   Units:	umol CO2 m-2 sec-1

   soil_moisture

   Soil volumetric water content (VWC) in percent integrated over the top 5 cm of soil. Measured with handheld Meter Group Inc., TEROS-10 just outside each collar after gas sampling. (Source: Producer Defined)

   Value	Definition
   empty cell	No measurement recorded due to flooded surface

   Range of values
   Minimum:	32
   Maximum:	74.1
   Units:	percent

   salinity

   Salinity in practical salinity units (psu) at time of chamber sampling measured within 2 meters of chamber collar in a ~30 cm deep 3 cm-diameter PVC well screened from 0 to 20 cm depth and equipped to continuously (15-minute intervals) monitor water-table depth relative to the soil surface, salinity, and water temperature (In-Situ Inc., Aqua TROLL 200). This is a specific subsample of a larger time series dataset. Full dataset available in O'Keefe Suttles and others, 2022.
   O'Keefe Suttles, J.A., Eagle, M.J., Sanders-DeMott, R., Nick, S.K., Brooks, T.W., Mann, A.G., and Kroeger, K.D., 2022, Continuous water level, salinity, and temperature data from coastal wetland monitoring wells, Cape Cod, Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P9T1KOTW. (Source: Producer Defined)

   Range of values
   Minimum:	0.143
   Maximum:	23.916
   Units:	psu

   dbs

   Water table depth relative to the soil surface in meters (where negative values indicate water level is below the soil surface and positive values indicate flooded conditions with water table above the soil surface) at time of chamber sampling. Measurements were within 2 meters of chamber collar in a ~30 cm deep 3 cm-diameter PVC well screened from 0 to 20 cm depth and equipped to continuously (15-minute intervals) monitor water-table depth relative to the soil surface, salinity, and water temperature (In-Situ Inc., Aqua TROLL 200). This is a specific subsample of a larger time series dataset. Full dataset available in O'Keefe Suttles and others, 2022.
   O'Keefe Suttles, J.A., Eagle, M.J., Sanders-DeMott, R., Nick, S.K., Brooks, T.W., Mann, A.G., and Kroeger, K.D., 2022, Continuous water level, salinity, and temperature data from coastal wetland monitoring wells, Cape Cod, Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P9T1KOTW. (Source: Producer Defined)

   Range of values
   Minimum:	-0.172
   Maximum:	0.267
   Units:	meters

   water_temp

   Water temperature in degrees Celsius at time of chamber sampling measured within 2 meters of chamber collar in a ~30 cm deep 3 cm-diameter PVC well screened from 0 to 20 cm depth and equipped to continuously (15-minute intervals) monitor water-table depth relative to the soil surface, salinity, and water temperature (In-Situ Inc., Aqua TROLL 200). This is a specific subsample of a larger time series dataset. Full dataset available in O'Keefe Suttles and others, 2022.
   O'Keefe Suttles, J.A., Eagle, M.J., Sanders-DeMott, R., Nick, S.K., Brooks, T.W., Mann, A.G., and Kroeger, K.D., 2022, Continuous water level, salinity, and temperature data from coastal wetland monitoring wells, Cape Cod, Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P9T1KOTW. (Source: Producer Defined)

   Range of values
   Minimum:	12.5
   Maximum:	20.053
   Units:	degrees Celsius

   soil_temp

   Soil temperature in degrees Celsius measured at 10 cm depth below the soil surface at the time of chamber sampling. This is a specific subsample of a larger time series dataset. Full dataset available in air_soil_temp_2021-2022.csv (part of this data release). (Source: Producer Defined)

   Range of values
   Minimum:	13.016
   Maximum:	21.62
   Units:	degrees Celsius

   air_temp

   Air temperature in degrees Celsius measured at 1 m height above the soil surface at the time of chamber sampling. This is a specific subsample of a larger time series dataset. Full dataset available in air_soil_temp_2021-2022.csv (part of this data release) (Source: Producer Defined)

   Range of values
   Minimum:	18.96
   Maximum:	32.0
   Units:	degrees Celsius

   par

   Photosynthetically active radiation (PAR) in micromoles photons per meter squared per second (umol photons m-2 sec-1) at the time of chamber sampling. (Source: Producer Defined)

   Range of values
   Minimum:	164.1
   Maximum:	2131.2
   Units:	umol photons m-2 sec-1

   air_soil_temp_2021-2022.csv

   Comma Separated Value (CSV) file containing data on soil and air temperature. The dataset has 307729 records. (Source: Producer Defined)

   datetime

   Date and time that sensor measurement was logged in local standard time (UTC - 05:00) in the format yyyy-mm-dd hh:mm:ss. (Source: Producer Defined) A numeric value representing date and time.

   site_name

   Site name of sampling location (Source: Producer Defined)

   Value	Definition
   Sage Lot Pond	A site located within the Waquoit Bay National Estuarine Research Reserve in Waquoit, MA.
   Flat Pond	A site located within the Waquoit Bay National Estuarine Research Reserve in Waquoit, MA.
   Woods Hole Park	A site located in the village of Woods Hole, MA.
   Quaker Meeting House	A site located within West Falmouth, MA.
   Herring River	A site located within the Cape Cod National Seashore in Wellfleet, MA.

   status

   Hydrological management status of the sampling location (Source: Producer Defined)

   Value	Definition
   Unrestricted	Indicates that the sampling location experiences natural, unrestricted tidal exchange.
   Impounded	Indicates that at this sampling location water is retained but tidal exchange is limited or excluded by infrastructure such as dikes, roads, or culverts

   veg_type

   Dominant vegetation at sampling location (Source: Producer Defined)

   Value	Definition
   Phragmites Wetland	Sampling location is a wetland dominated by Phragmites australis
   Typha/Schoenoplectus Wetland	Sampling location is a wetland dominated by Typha lattifolia and Schoenoplectus

   sampling_location_name

   Sampling location name indicating both the hydrological management and salinity status relative to the geographical site as referenced in the related publication (Sanders-DeMott and others, 2022) (Source: Producer Defined)

   Value	Definition
   Unrestricted-High	Sampling location that experiences natural, unrestricted tidal exchange and is the high salinity plot of the site pair at Sage Lot Pond as referenced in the related publication (Sanders-DeMott and others, 2022)
   Unrestricted-Low	Sampling location that experiences natural, unrestricted tidal exchange and is the low salinity plot of the site pair at Sage Lot Pond as referenced in the related publication (Sanders-DeMott and others, 2022)
   Impounded-FPP	Sampling location that experiences tidal exchange that is limited or excluded and is located in a Phragamites stand at Flat Pond
   Impounded-FPTS	Sampling location that experiences tidal exchange that is limited or excluded and is located in a mixed Typha latifolia and Schoenoplectus stand at Flat Pond
   Impounded-WH	Sampling location that experiences tidal exchange that is limited or excluded and is located in Woods Hole Park in Woods Hole, MA
   Impounded-QMH	Sampling location that experiences tidal exchange that is limited or excluded and is located on Quaker Meeting House property in West Falmouth, MA
   Impounded-High	Sampling location that experiences tidal exchange that is limited or excluded and is the high salinity plot of the site pair at Herring River as referenced in the related publication (Sanders-DeMott and others, 2022)
   Impounded-Low	Sampling location that experiences tidal exchange that is limited or excluded and is the low salinity plot of the site pair at Herring River as referenced in the related publication (Sanders-DeMott and others, 2022)

   latitude

   Latitude decimal degrees north, NAD83 (Source: Producer Defined)

   Range of values
   Minimum:	41.52952
   Maximum:	41.93784
   Units:	decimal degrees

   longitude

   Longitude decimal degrees west, NAD83. The negative value indicates a location in the western hemisphere. (Source: Producer Defined)

   Range of values
   Minimum:	-70.67029
   Maximum:	-70.05472
   Units:	decimal degrees

   air_temp_1m

   Air temperature recorded at 1 meter height above the sediment surface (Source: Producer Defined)

   Value	Definition
   empty cell	No Data due to instrument malfunction

   Range of values
   Minimum:	-20.9
   Maximum:	39.0
   Units:	degrees Celsius

   soil_temp

   Soil temperature recorded at 10 cm depth below the sediment surface (Source: Producer Defined)

   Value	Definition
   empty cell	No Data due to instrument malfunction

   Range of values
   Minimum:	0.9
   Maximum:	24.8
   Units:	degrees Celsius

   sensor

   Sensor manufacturer and model (Source: Producer Defined)

   Value	Definition
   HOBO U23-003 Temp/Temp	Manufacturer and model of sensor used to record both air and soil temperature
   HOBO MX2303 Temp/Temp	Manufacturer and model of sensor used to record both air and soil temperature

   slp_met_2021-2022.csv

   Comma Separated Value (CSV) file containing meteorological data. This dataset has 36069 records. (Source: Producer Defined)

   datetime

   Date and time that sensor measurement was logged in local standard time (UTC - 05:00) in the format yyyy-mm-dd hh:mm:ss. (Source: Producer Defined) A numeric value representing date and time.

   site_name

   Site of the sampling location (Source: Producer Defined)

   Value	Definition
   Sage Lot Pond	A site located within the Waquoit Bay National Estuarine Research Reserve in Waquoit, MA.

   status

   Hydrological management status of the sampling location (Source: Producer Defined)

   Value	Definition
   Unrestricted	Indicates that the sampling location experiences natural, unrestricted tidal exchange.

   veg_type

   Dominant vegetation at sampling location (Source: Producer Defined)

   Value	Definition
   Phragmites Wetland	Sampling location is a wetland dominated by Phragmites australis

   latitude

   Latitude decimal degrees north, NAD83 (Source: Producer Defined)

   Range of values
   Minimum:	41.55773
   Maximum:	41.55773
   Units:	decimal degrees

   longitude

   Longitude decimal degrees west, NAD83. The negative value indicates a location in the western hemisphere. (Source: Producer Defined)

   Range of values
   Minimum:	-70.50443
   Maximum:	-70.50443
   Units:	decimal degrees

   air_temp_3m

   Air temperature recorded at 3 meters height above the sediment surface with Onset HOBO Temperature/RH Smart Sensor S-THB-M00x (Source: Producer Defined)

   Value	Definition
   empty cell	No Data due to instrument malfunction.

   Range of values
   Minimum:	-12.6
   Maximum:	33.9
   Units:	degrees Celsius

   RH

   Relative humidity recorded at 3 meters height above the sediment surface with Onset HOBO Temperature/RH Smart Sensor S-THB-M00x (Source: Producer Defined)

   Value	Definition
   empty cell	No Data due to instrument malfunction.

   Range of values
   Minimum:	20.5
   Maximum:	100.0
   Units:	percent

   PAR

   Incoming photosynthetically active radiation (PAR) in micromoles photons per meter squared per second (umol photons m-2 sec-1) recorded at 3 meters height above the sediment surface with Onset HOBO Photosynthetically Active Radiation Smart Sensor S-LIA-M003 (Source: Producer Defined)

   Value	Definition
   empty cell	No Data due to instrument malfunction.

   Range of values
   Minimum:	1.2
   Maximum:	2511.2
   Units:	umol photons m-2 sec-1

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Rebecca Sanders-DeMott
   • Meagan J. Eagle
   • Kevin D. Kroeger
   • Thomas W. Brooks
   • Jennifer A. O'Keefe Suttles
   • Sydney K. Nick
   • Adrian G. Mann
   • Sophie Kuhl
   • Simone Gibson
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   Rebecca Sanders-Demott

   U.S. Geological Survey, NORTHEAST REGION

   384 Woods Hole Road

   Woods Hole, MA
   

   US

   508-548-8700 x2255 (voice)

   rsanders-demott@usgs.gov

Why was the data set created?

How was the data set created?

1. From what previous works were the data drawn?
2. How were the data generated, processed, and modified?

   Date: 15-Oct-2021 (process 1 of 6)

   Six sampling locations were established across several villages of Falmouth, MA for static chamber sampling. Two sampling locations were established at a site with natural, unrestricted tidal exchange at Sage Lot Pond, two in an impounded marsh at Flat Pond, one site in West Falmouth behind a Quaker Meeting House, and one site in Woods Hole behind Woods Hole Park. Each sampling location was equipped with three replicate collars for static chamber measurements and one pair of air/soil temperature sensors. The two sites at Sage Lot Pond were part of a prior study established in 2020 and data collected in 2020 from those sites is available at https://www.sciencebase.gov/catalog/item/62557ae8d34e21f8276f4879.
   To facilitate static chamber CH4 and CO2 flux measurements, round PVC collars (55 cm inner diameter, 24 cm height, 3 replicates per sampling location (n = 6)) were inserted into the sediment surrounding intact vegetation to a depth of at least 10 cm more than four weeks prior to initial sampling to allow the soil to equilibrate from disturbance. On each sample collection date, we used a modular system of clear, round acrylic chambers to enclose the vegetation and sediment surface for flux measurement. Chamber sections were 55 cm diameter and 0.91 meters (m) tall. Depending on the height of the vegetation at the sampling location we used either one, two, or three stacked chambers for a total chamber height of 0.91, 1.83 or 2.74 m and empty chamber volume of 0.22, 0.43 or 0.64 cubic meters (m3). The topmost chamber always had a transparent lid permanently affixed with silicone caulking and a vent tube to allow for pressure equilibration. Two battery-powered fans (10 cm in diameter) were attached to the inside of the chamber to homogenize air and temperature sensors (HOBO TidbiT v2, Onset Computer Corporation) were mounted to the inside of the top and bottom chambers to record chamber air temperature. All samples were collected during mid-day hours between 10:00-14:00 local standard time. Chamber air was considered equilibrated based on visual inspection of the stability of a linear concentration change in the gases of interest, this was typically less than 60 seconds.
   Field data required to calculate fluxes (i.e., chamber head space, chamber deployment time) were recorded on field datasheets and later entered into electronic spreadsheets. Concentrations of CH4 and CO2 during 2-5 minutes incubations were measured and recorded using a portable optical feedback-cavity enhanced absorption spectrometer (LI-7810 CH4/CO2/H2O Trace Gas Analyzer, LI-COR, Inc.) sampling at 1 Hz. Chamber flux incubations were conducted both in the light with transparent chambers to quantify net ecosystem exchange, and in the dark with opaque covering of the chambers to quantify ecosystem respiration in the absence of photosynthesis.
   We used a sliding regression (“rollRegres” package in R, Christoffersen, 2019) to identify the 120-second window during the incubation where a simple linear regression of CH4 or CO2 concentration by time had a maximum R2. We verified that all linear models used to calculate flux had a significant slope (p less than 0.001) and an RMSE ≤ 1 ppm for CO2 and ≤ 10 ppb for CH4. Four CO2 measurements did not have a slope significantly different than 0, and therefore those fluxes were set to 0. Three additional CO2 measurements were rejected for low R2 and RMSE > 1 ppm.
   We also assessed each incubation for non-linear changes in CH4 concentration over time as a signal of potential ebullition. When potential ebullition was observed, in addition to applying the sliding regression described above, we estimated CH4 concentration change based on the initial and final concentration of CH4 gas (VCS, 2015).
   The rate of concentration change of CO2 and CH4 (slope or the difference between final and initial when ebullition was suspected) was converted to an area-based flux using the Ideal Gas Law and the volume and footprint of the chamber, along with measured chamber air temperature (pooled across the two temperature sensors). Calculations were executed with the “conc_to_flux” function in the R package “ecoflux” (Shannon, 2018).
   This process step and all subsequent process steps (unless otherwise noted) were performed by the same person, Rebecca Sanders-Demott.
   Christoffersen, B., 2019, rollRegres: Fast Rolling and Expanding Window Linear Regression. R package version 0.1.3. https://CRAN.R-project.org/package=rollRegres
   Shannon, J., 2018, ecoFlux: Functions for ecological flux studies including sap flux and soil/stem C efflux (0.3.1). https://rdrr.io/github/jpshanno/ecoflux/
   Verified Carbon Standard (VCS), 2015, Approved VCS Methodology VM 0033: Methodology for Tidal Wetland and Seagrass Restoration. Version 1.0, 20 November 2015, Sectoral Scope 14. Developed by Verra with Restore America’s Estuaries and Silvestrum. 1–115. https://verra.org/wp-content/uploads/2018/03/VM0033-Tidal-Wetland-and-Seagrass-Restoration-v1.0.pdf Person who carried out this activity:
   

   Rebecca Sanders-Demott

   U.S. Geological Survey, NORTHEAST REGION

   384 Woods Hole Road

   Woods Hole, MA
   

   US

   508-548-8700 x2255 (voice)

   rsanders-demott@usgs.gov

   Date: 15-Oct-2021 (process 2 of 6)

   Soil volumetric water content (VWC) integrated over the top 5 cm was measured (Meter Group Inc., TEROS-10) just outside each collar after gas sampling. Values were recorded by hand on a field data sheet and later entered into an electronic spreadsheet.

   Date: 15-Oct-2021 (process 3 of 6)

   Photosynthetically active radiation (PAR) was measured concurrent with chamber sampling with a PAR sensor (Onset Photosynthetically Active Radiation (PAR) Smart Sensor, model S-LIA-M003) deployed on a portable 4-meter tall tripod mast that was set up adjacent to each site during sampling. Data were logged every 1 minute from the time we arrived on site until chamber sampling was completed on an Onset HOBO USB Microstation Logger. When daily sampling was completed, data files were downloaded to a field laptop via HOBOware software (version 3.7.2.1), converted to .csv files, and matched by timestamp to the chamber incubation data via R.

   Date: 18-May-2022 (process 4 of 6)

   At each chamber sampling location, the three replicate collars were paired with one soil temperature sensor (10 cm depth) and one air temperature sensor (1 m height) mounted on a PVC well in April 2021. Air and soil temperature were logged every 15 minutes. Raw data files were downloaded in the field monthly. Ultimately all data were uploaded as .hobo files to the Woods Hole Coastal and Marine Science Center (WHCMSC) network server. Raw data files were converted to CSV files in the software: HOBOware (version 3.7.2.1). Data were plotted to check for any irregularities in sensor functioning (e.g. outliers or unrealistic values). All found irregularities were removed from the final dataset.

   Date: 18-Nov-2021 (process 5 of 6)

   Latitude and longitude of each chamber and sensor location, along with elevation of chambers was measured with a Trimble Real-Time Kinematic (RTK) GPS. Accuracy was 2-3 cm according to instrument corrections. Data files were exported from the instrument via a .csv file and appended to the data files of calculated fluxes or sensors via R.

   Date: 15-Apr-2022 (process 6 of 6)

   After all chamber flux data were finalized, we exported the sensor data (logged at 15-minute intervals) that most closely matched the timestamp of the chamber incubation and appended those values to the chamber fluxes data table using R for user convenience. Sensor data included are air and soil temperature described here and availanble in the file air_soil_temp_2021-2022.csv (part of this data release), as well as data on water temperature, water table depth below surface, and salinity, which are available in O'Keefe Suttles and others, 2022.
   O'Keefe Suttles, J.A., Eagle, M.J., Sanders-DeMott, R., Nick, S.K., Brooks, T.W., Mann, A.G., and Kroeger, K.D., 2022, Continuous water level, salinity, and temperature data from coastal wetland monitoring wells, Cape Cod, Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P9T1KOTW.

3. What similar or related data should the user be aware of?
   Sanders-DeMott, Rebecca, Eagle, Meagan J., Kroeger, Kevin D., Wang, Faming, Brooks, Thomas W., O'Keefe Suttles, Jennifer A., Nick, Sydney K., Mann, Adrian G., and Tang, Jianwu, 2022, Impoundment increases methane emissions in Phragmites-invaded coastal wetlands: Global Change Biology DOI:10.1111/gcb.16217, Wiley, Hoboken, New Jersey.

   Online Links:

   • https://doi.org/10.1111/gcb.16217

   Other_Citation_Details:

   Journal article based on prior data from some of the sampling locations included in this data release.

   Jennifer A. O'Keefe Suttles, Eagle, Meagan J., Sanders-DeMott, Rebecca, Nick, Sydney K., Brooks, Thomas W., Mann, Adrian G., and Kroeger, Kevin D., 2022, Continuous Water Level, Salinity, and Temperature Data from Coastal Wetland Monitoring Wells, Cape Cod, Massachusetts: data release DOI:10.5066/P9T1KOTW, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.5066/P9T1KOTW
   • https://www.sciencebase.gov/catalog/item/624b1581d34e21f827635bd0

   Other_Citation_Details:

   Provides continuous data on water level, salinity, and water temperature concurrent with chamber flux measurements presented in this data release.

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?
   The LI-7810 CH4/CO2/H2O Trace Gas Analyzer has a precision of 0.60 parts per billion (ppb) at 2 parts per million (ppm) with 1 second averaging for methane (CH4) and of 3.5 ppm at 400 ppm with 1 second averaging for carbon dioxide (CO2). The instrument calibration was checked using laboratory calibration gases prior to field measurements in spring 2020. All calculated slopes used to calculate fluxes were subject to statistical checks as outlined in Process Step 1. Each sampling location was measured in triplicate for gas fluxes and with ten replicates for biomass assessments to reduce uncertainty. Manufacturer's specifications for the dual channel temperature logger (used in this study for continuous measurement of soil and air (-10 cm and 1 m respectively from land surface; Onset, model type HOBO U23 Pro v2 and MX2303) for accuracy is +/- 0.21 degrees Celsius from 0 degrees Celsius to 50 degrees Celsius; the manufacturer's specification for resolution is 0.02 degrees Celsius at 25 degrees Celsius. Accuracy of the photosynthetically active raditation (PAR) sensor +/- 5 micromoles per meter squared per second and resolution of the PAR sensor is 2.5 micromoles per meter squared per second. Relative humidty (RH) sensor was enclosed within a solar radiation shield and deployed on a mast with other meteorological sensors. Typical accuracy of the RH sensor is +/-2.5 percent and resolution is 0.1 percent RH. No formal attribute accuracy tests were conducted.
2. How accurate are the geographic locations?
   Latitude and Longitude were measured for each of the chamber gas sampling collars (3 per sampling location) and the paired soil and air temperature sensors (1 per sampling location) by Trimble Real-Time Kinematic (RTK) GPS at the end of the sampling season. Recorded Horizontal Dilution of Precision (HDOP) was 0.600 or less for all measurements. Average horizontal accuracy of this method is +/- 30 centimeters. No formal positional accuracy tests were conducted.
3. How accurate are the heights or depths?
   Land surface elevations were measured for each of the chamber gas sampling collars (3 per sampling location) and the paired soil and air temperature sensors (1 per sampling location) by Trimble Real-Time Kinematic (RTK) GPS at the end of the sampling season. Recorded Vertical Dilution of Precision (VDOP) was 0.900 or less for all measurements. Average vertical accuracy of this method is +/- 5 centimeters. No formal positional accuracy tests were conducted.
4. Where are the gaps in the data? What is missing?
   Gaps in the continuous data record for a given parameter may have been the result of one of several sources: sensor not deployed during that time period, vandalism of an instrument by humans or destruction by chewing animals, removal of an instrument for maintenance, corrupt data file due to malfunctioning instrument, or data excluded based on quality assessment described in process step. Exclusions of data from the continuous record are coded as blank cells.
5. How consistent are the relationships among the observations, including topology?
   Each logged parameter set was queried for maximum and minimum values to be sure logged data fell within expected ranges for the environmental conditions.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   ScienceBase

   U.S. Geological Survey

   Denver Federal Center, Building 810, Mail Stop 302

   Denver, CO
   

   United States

   1-888-275-8747 (voice)

   sciencebase@usgs.gov
2. What's the catalog number I need to order this data set? The dataset contains three CSV files containing the data (chamber_fluxes_2021.csv; air_soil_temp_2021-2022.csv; slp_met_2021-2022.csv), the browse graphic (phragmites_chamber.jpg), and the FGDC CSDGM metadata in XML format.
3. What legal disclaimers am I supposed to read?
   Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	The data release includes 3 comma separated files, a browse graphic, and the FGDC CSDGM metadata. in format CSV (version Microsoft Excel Office 365) Size: 1
     Network links:	https://www.sciencebase.gov/catalog/file/get/629fa3e2d34ec53d276fd537 https://www.sciencebase.gov/catalog/item/629fa3e2d34ec53d276fd537 https://doi.org/10.5066/P9RRL3T0

   • Cost to order the data: None

5. What hardware or software do I need in order to use the data set?
   The data release includes 3 comma-delimited text files. The user must have software capable of opening the text file and reading the data formats.

Who wrote the metadata?

Dates:

Last modified: 15-Jun-2022

Metadata author:

Rebecca Sanders-Demott

U.S. Geological Survey, NORTHEAST REGION

384 Woods Hole Road

Woods Hole, MA

US

508-548-8700 x2255 (voice)

whsc_data_contact@usgs.gov

Contact_Instructions:

The metadata contact email address is a generic address in the event the person is no longer with USGS.

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)