Data from: CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana
Data files
Oct 16, 2024 version files 27.41 KB
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CO2_fluxes_TQ.xlsx
19.66 KB
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README.md
7.76 KB
Abstract
This dataset consists of carbon (C) flux measurements in May, July and September 2017 collected in a 2-year old created and a nearby natural reference marsh in the Chenier Plain Region of Louisiana. The purpose of this study was to examine seasonal C fluxes, specifically, gross ecosystem production (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE) of CO2 in unvegetated and vegetated (Spartina alterniflora) areas of a 2-year old created marsh and Spartina alterniflora and Spartina patens communities in a ‘natural’ reference brackish marsh. We also collected plant biomass, sediment chlorophyll a concentrations, marsh elevation, soil nitrogen and organic matter and bulk density to test for relationships to carbon fluxes.
README: Data from: CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana
https://doi.org/10.5061/dryad.xsj3tx9qt
Description of the data and file structure
README
Reference Information
Provenance for this README
*File Name: README_Dataset-CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana.txt
*Authors: Tracy Quirk
*Other contributors: Andy Muench, John White, Ron DeLaune
*Date Created:2024-09-20
Dataset Version and Release History
* Current Version:
* Number: 1.0.0
* Date: 2024-09-20
* Persistent identifier:
* Summary of changes: n/a
* Embargo Provenance: n/a
* Scope of embargo: n/a
* Embargo period: n/a
Dataset Attribution and Usage
* Dataset Title: "CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana"
* Dataset Contributors:
* Creators: Tracy Quirk, Andy Muench, John White and Ron DeLaune
* Date of Issue: 2024-08-21
* Publisher: Louisiana State University
* License: Use of these data is covered by the following license:
* Title: CC0 1.0 Universal (CC0 1.0)
* Specification: https://creativecommons.org/publicdomain/zero/1.0/; the authors respectfully request to be contacted by researchers interested in the re-use of these data so that the possibility of collaboration can be discussed.
* Suggested Citations:
Dataset citation:
\> Quirk, T. et al. 2024. "Dataset: CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana", Dryad,
Contact Information
* Name: Tracy Quirk
* Affiliations: Department of Oceanography and Coastal Sciences, Louisiana State University
* ORCID ID: https://orcid.org/0000-0002-2068-592X
* Email: tquirk@lsu.edu
* Address: e-mail preferred
Additional Dataset Metadata
Acknowledgements
* Funding sources: NOAA-Louisiana Sea Grant #: NA140AR4170099
Dates and Locations
* Dates of field sampling: May, July, and September 2017
* Geographic location: Sabine National Wildlife Refuge, Calcasieu, Louisiana
Methodological Information
* Experimental Design:
Ten plots were established in two marshes in the Chenier Plain Region, southwest Louisiana in Sabine National Wildlife Refuge, Hackberry, Louisiana. The marshes were brackish marshes: one was created using dredge sediment in 2015 and was largely unvegetated at the time of the study in 2017 but had sparse clones of Spartina alterniflora that were naturally colonizing and spreading and the other marsh was a natural reference marsh dominated by Spartina alterniflora and Spartina patens along with some other species. Five plots were established in unvegetated areas and five plots in Spartina alterniflora areas of the created marsh and five plots each in Spartina alterniflora and Spartina patens in the natural reference marsh for measurement of carbon dioxide (CO2) fluxes to calculate gross ecosystem productivity (GEP; gross uptake of CO2 by plants and algae), ecosystem respiration (ER; CO2 respiration from primary producers and heterotrophs including microbial decomposers), and net ecosystem exchange (NEE; a measure of the net sink or source of CO2 based on the net of uptake through photosynthesis and losses through respiration). Chambers were established in all plots and CO2 fluxes were measured in May, July and September 2017 within clear chambers for NEE and opaque chambers for ER. Plant biomass, plot elevation, soil nitrogen availability and soil organic matter content and bulk density were also collected to examine relationships to carbon fluxes. Two measures of soil nitrogen were used: extractable ammonium and potentially mineralizable nitrogen.
\- Marsh type: Natural Reference and Created
\- Habitat: Natural Reference: Spartina alterniflora and Spartina patens; Created: unvegetated and Spartina alterniflora (n = 5)
\- Month: May, July and September
Data and File Overview
Summary Metrics
* File count: 1
* Total file size: 13 KB
* File formats: .csv
File Details
Details: CO2 fluxes_TQ.csv
* Description: a comma-delimited file containing temperature, photosynthetically active radiation, Gross Ecosystem Productvity (GEP), Ecosystem Respiration (ER), Net Ecosystem Exchange (NEE), marsh elevation, plant biomass, sediment chlorophyll a, extractable ammonium (NH4+) and potential mineralizable nitrogen (PMN), soil organic matter content (%) and soil bulk density for two soil depths (0 - 10 cm and 10 - 20 cm).
* Format(s): .csv
* Size(s): 16 KB
* Dimensions: 61 rows X 21 columns
* Variables:
\* Marsh Type: Created or Natural
\* Veg: Bare (unvegetated), Salt (Spartina alterniflora), Spat (Spartina patens)
\* Treatment: CB (created bare), CS (created Salt), NSa (natural Salt), NSp (natural Spat)
\* Plot #: 1 - 10
\* TEMP: average temperature in celsius in chamber
\* AVG PAR: average PAR (photosynthetically active radiation) in chamber
\* GEP (umol s-1 m-2): Gross Ecosystem Productivity (positive = C-uptake)
\* ER (umol s-1 m-2): Ecosystem Respiration
\* Elevation (m, NAVD88): marsh elevation in meters relative to the datum North American Vertical Datum 1988
\* NEE (umol s-1 m-2): Net Ecosystem Exchange (balance of GEP and ER)
\* Sed chl a (mg/kg soil): sediment chloropyll a concentration
\* Plant biomass (g/m2):aboveground biomass
\* Soil org matter (%) 0 - 10 cm:percent soil organic matter in 0 - 10 cm depth
\* Soil org matter (%) 10 - 20 cm:percent soil organic matter in 10 - 20 cm depth
\* Soil bulk density (g cm-3) 0 - 10 cm: soil bulk density in 0 - 10 cm depth
\* Soil bulk density (g cm-3) 10 - 20 cm:soil bulk density in 0 - 10 cm depth
\* NH4 0 -10 cm (ug cm-3):extractable ammonium (NH4+) in 0 - 10 cm depth
\* NH4 10 - 20 cm (ug cm-3):extractable ammonium (NH4+) in 10 - 20 cm depth
\* PMN 0 -10 cm (ug cm-3 d-1): potential mineralizable nitrogen in 0 - 10 cm depth
\* PMN 10 - 20 cm (ug cm-3 d-1):potential mineralizable nitrogen in 10 - 20 cm depth
* Missing data codes: blank cell
END OF README
Files and variables
File: CO2_fluxes_TQ.csv
Description:
Variables
- * Marsh Type: Created or Natural
* Veg: Bare (unvegetated), Salt (Spartina alterniflora), Spat (Spartina patens)
* Treatment: CB (created bare), CS (created Salt), NSa (natural Salt), NSp (natural Spat)
* Plot #: 1 - 10
* TEMP: average temperature in celsius in chamber
* AVG PAR: average PAR (photosynthetically active radiation) in chamber
* GEP (umol s-1 m-2): Gross Ecosystem Productivity (positive = C-uptake)
* ER (umol s-1 m-2): Ecosystem Respiration
* Elevation (m, NAVD88): marsh elevation in meters relative to the datum North American Vertical Datum 1988
* *NEE (umol s-1 m-2): Net Ecosystem Exchange (balance of GEP and ER)
* * Sed chl a (mg/kg soil): sediment chloropyll a concentration
* Plant biomass (g/m2):aboveground biomass
* Soil org matter (%) 0 - 10 cm:percent soil organic matter in 0 - 10 cm depth
* Soil org matter (%) 10 - 20 cm:percent soil organic matter in 10 - 20 cm depth
* Soil bulk density (g cm-3) 0 - 10 cm: soil bulk density in 0 - 10 cm depth
* Soil bulk density (g cm-3) 10 - 20 cm:soil bulk density in 0 - 10 cm depth
* NH4 0 -10 cm (ug cm-3):extractable ammonium (NH4+) in 0 - 10 cm depth
* NH4 10 - 20 cm (ug cm-3):extractable ammonium (NH4+) in 10 - 20 cm depth
* PMN 0 -10 cm (ug cm-3 d-1): potential mineralizable nitrogen in 0 - 10 cm depth
* PMN 10 - 20 cm (ug cm-3 d-1):potential mineralizable nitrogen in 10 - 20 cm depth
Methods
For this study, we tested seasonal carbon dioxide fluxes in unvegetated and newly vegetated (with Spartina alterniflora) areas of a 2-year old Created coastal marsh constructed in 2015 and in two vegetated communities (Spartina alterniflora and Spartina patens) a nearby ‘natural’ Reference marsh. The Reference marsh is representative of remnant brackish marshes in this system that have been subject to indirect human alterations of hydrology combined with natural changes to the system. The Reference marsh was dominated by a mix of species with stands of S. alterniflora at lower elevations and S. patens at higher elevations. At the time of the study in 2017, the 2-year old Created marsh had large unvegetated areas and sparse clones of S. alterniflora, which expanded over the study period. Clone patches of S. alterniflora in the Created marsh were heterogeneous, varying in size and biomass.
Carbon fluxes
Four habitats were the focus of this study, two representative of the Created marsh: (1) unvegetated sediments, where algae and microphytobenthos may be dominant primary producers (‘UC’); and (2) newly colonized S. alterniflora clones (‘SaC’); and two in the Reference marsh: (3) S. alterniflora (‘SaR’); and (4) S. patens (‘SpR’). Carbon dioxide fluxes were measured in five replicate plots randomly located in each habitat type using the static chamber method (n = 5). Plots were at least 10 m apart. Gas chambers for the vegetated treatments consisted of a 30 cm3 acrylic base unit placed to a depth 10 cm below the surface approximately one month prior to the first set of measurements. The base unit was left in place throughout the study. In May, July and September 2017, one to three stackable 30 cm3 acrylic chambers were assembled to accommodate the height of the tallest vegetation in each of the five plots per habitat. A base of one top unit was used for the non-vegetated plots in the created marsh. To ensure an air-tight seal, a water-filled collar surrounded the base of each stackable unit to limit external gas diffusion into the chamber. Carbon dioxide concentration was measured using an EGM-4 (PP Systems©, Amesbury, MA) infra-red gas analyzer to the nearest part per million at 1-minute intervals for 10 to 20 minutes or until the concentration was below the detection limit (~250 ppm). Net ecosystem exchange (NEE) was measured using transparent chambers while ecosystem respiration (ER) was measured using opaque chamber units. ER measurements were collected in the same plots following measurements of NEE and a 20 minute equilibration period once opaque chambers were established to allow photosynthesis to cease.
Net ecosystem exchange and ER have been found to vary with temperature and levels of photosynthetically active radiation (PAR). Therefore, temperature and PAR were measured along with CO2 concentration using a probe attached to the EGM-4 (PP Systems©, Amesbury, MA).
CO2-flux calculations
NEE and ER were determined by linear regression of CO2 change during the sampling interval where a strong linear slope was present. The slope of that regression was used as either the NEE (clear chamber) or ER (opaque chamber). The slope for NEE was only taken when full sunlight occurred in the sampling interval which is generally 1000 µmol m-2s-1 or greater.
The amount of CO2 in the chamber at a given time was calculated as:
CO2 µmol = CO2 ppm / (22.4*(273+C)/273) * 27X
The coefficient X is the number of chamber units stacked at each plot. Each chamber unit contains 27 liters of air, and therefore X was multiplied by 27. The coefficient C is the temperature (°C) at the time of measurement. It should be noted that 22.4 is the molar volume of CO2 at the pressure 1 ATM and 0°C. Our sites are at approximate sea level and thus are generally at 1 ATM pressure. Temperatures within the chambers were between 25 and 40°C and therefore temperature was corrected for in the above equation.
The GEP was calculated as:
GEP= -(NEE) + ER
Negative GEP and NEE indicates gross and net C uptake, respectively. It was assumed that respiration rate during the dark incubations was equal to the respiration rate during daylight conditions, but this may not be the case as leaf respiration tends to increase under dark conditions (Brooks and Farquhar, 1985; Kromer, 1995; Atkin et al. 1997; Schulz, 2003).
Algal and plant biomass
To examine variation in algal biomass across treatments, sediment was collected adjacent to each gas exchange plot for chlorophyll a analysis during each sampling in May, July, and September. Chlorophyll a content was determined from the top 2 cm of sediment by using sonication and 90% acetone (modified from Welschmeyer, 1994). Approximately 0.2 g of the sampled sediment was placed in 90% acetone, centrifuged at 5000 X g for 5 minutes, and then sonicated. Following sonication for 30 seconds, the samples were placed in a freezer for one day and then centrifuged again at 5000 X g for 5 minutes again the next day. Chl a content was then measured using a fluorometer (Turner Designs TD-700).
Aboveground biomass was estimated using stem height and density measurements taken within the study plots in July and September 2017. The heights of up to 15 randomly chosen stems was collected in each plot. Stem density was determined by counting the number of stems within 0.09 m2 for S. alterniflora, 0.01 m2 for S. patens. To estimate the biomass of S. alterniflora in the Reference marsh, the following equation was used for Spartina alterniflora in the region (Elsey-Quirk, unpublished data):
AB = - 2032 + 521(log height) + 136(log density)
The equation used for S. alterniflora in the Reference marsh was not used for S. alterniflora in the created marsh because the relationships between stem height, density and biomass may differ due to different soil or nutrient conditions. For S. alterniflora in the created marsh and S. patens in the Reference marsh a coefficient relating height and density was derived from data in a previous study in the same marshes where stem height, stem density, and biomass were measured (Abbott et al. 2019). The coefficient was determined from the average biomass divided by the product of stem density and average stem height.
The equation used for S. alterniflora in the created marsh was:
AB = 0.0755(height)(density)
The equation used for S. patens in the Reference marsh was:
AB = 0.0058(height)(density)
For all equations, height was measured in cm, density in stems m-2, and biomass in g m-2.
Environmental factors
Elevation (NAVD88) was measured at each plot using Leica Real Time Kinematic GS14. Three elevations were taken at each plot and then averaged to estimate the elevation. Horizontal and vertical accuracies of the measurements were 1 and 2 cm, respectively.
Sediment cores (7 cm diameter by 20 cm depth) were collected from each plot by hand in May 2017 using a plastic core barrel. Two depth intervals of 0-10 and 10-20 cm were sectioned and analyzed for bulk density, soil organic matter content via loss on ignition (LOI), and soil nitrogen availability. Soil bulk density was measured for each depth section by drying to a constant weight at 60°C and dividing by the volume. A 1-g portion of the dried subsample was then combusted in a muffle furnace at 550°C for four hours. Soil organic matter was calculated by the proportion of sample lost on ignition.
Two measures of sediment nitrogen availability were made. Extractable ammonium (NH4+) was used to indicate the availability of nitrogen for primary producers in marsh sediment measured as mg N kg-1 and potentially mineralizable nitrogen (PMN) was used to measure of the rate at which extractable NH4+ increases with time in the sediment as an indicator of microbial-mediated ammonification (White and Reddy, 2000). For extractable NH4+, 5 g of homogenized sediment sample from each depth section of each core was placed into a 50-ml centrifuge tube with 20 ml of 2 M L-1 KCL. Tubes were placed into a horizontal shaker for one hour and then centrifuged at 5000 g for 10 minutes. Samples were filtered through 0.45 um glass fiber filters into scintillation vials and preserved with H2SO4. Extractable NH4+ was determined using an AQ2 Automated Discrete Analyzer (Seal Analytical Inc.) via colorimetric analysis.
PMN was determined by measuring extractable NH4+ at days 0, 2, 5, and 10 of incubation under anerobic conditions. Day 0 was determined from initial extractable NH4+ concentrations from the soil samples. Three subsamples of each soil sample were homogenized,placed into glass serum bottles, which were evacuated and replaced with 99.99% N2. The bottles were then injected with 20 ml of 10 psu salinity water purged by N2 gas and placed into an incubator (IS-971R, Jeio Tech) at 40°C, continually oscillating at 100 rpm. The replicate serum bottles were removed at day 2, 5, and 10 and extracted with 25 ml of 2 M L-1 KCl. Vials were placed into a horizontal shaker for one hour and then centrifuged at 5000 g for 10 minutes. Samples were filtered through 0.45-um membrane filters into 20 ml scintillation vials and preserved with concentrated sulfuric acid to a pH < 2. Extractable NH4+ was determined using an AQ2 Automated Discrete Analyzer (Seal Analytical Inc.) for colorimetric analysis of the samples (USEPA, 1993). PMN was determined for each sample using linear regression of extractable NH4+ vs time.