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Delta-X: Aboveground Vegetation Structure for Herbaceous Wetlands across MRD, LA, USA

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Documentation Revision Date: 2022-06-26

Dataset Version: 1.1

Summary

This dataset provides mean stem diameter, mean height, dominant species, hydrogeomorphic zone (HGM), and stem density for vegetation in herbaceous wetlands collected in the Atchafalaya and Terrebonne basins in southeastern coastal Louisiana. The data were collected between 2021-03-21 to 2021-03-31 during the Delta-X Spring 2021 deployment, and from 2021-08-19 to 2021-08-27 during the Fall deployment. Field measurements were conducted at six sites in the Atchafalaya (N = 3) and Terrebonne (N = 3) basins. Five of the sites were adjacent to sites from the Coastwide Reference Monitoring System (CRMS), and the other site was in the Wax Lake Delta (WLD) without appropriate adjacent CRMS sites. Sites in both basins were chosen to represent a salinity gradient including freshwater, brackish, and saline ecosystems. Vegetation structure was measured in replicate sample plots (0.25 m2) located along transects oriented perpendicular to wetland edge to capture a range of hydrogeomorphic zones (supratidal and intertidal).

This dataset includes two files in comma-separated values (*.csv) format.

Figure 1: Aboveground vegetation sorted by species into biomass and necromass components.

Citation

Castañeda-Moya, E., and E. Solohin. 2021. Delta-X: Aboveground Vegetation Structure for Herbaceous Wetlands across MRD, LA, USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1997

Table of Contents

  1. Dataset Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References

Dataset Overview

This dataset provides mean stem diameter, mean height, dominant species, hydrogeomorphic zone (HGM), and stem density for vegetation in herbaceous wetlands collected in the Atchafalaya and Terrebonne basins in southeastern coastal Louisiana. The data were collected during the Delta-X Spring and Fall deployments in March and August, 2021 respectively. Field measurements were conducted at six sites in the Atchafalaya (N = 3) and Terrebonne (N = 3) basins. Five of the sites were adjacent to sites from the Coastwide Reference Monitoring System (CRMS; Steyer et al., 2003), and the other site was in the Wax Lake Delta (WLD) without appropriate adjacent CRMS sites. Sites in both basins were chosen to represent a salinity gradient including freshwater, brackish, and saline ecosystems. Vegetation structure was measured in replicate sample plots (0.25 m2) located along transects oriented perpendicular to wetland edge to capture a range of hydrogeomorphic zones (supratidal and intertidal).

Project: Delta-X

The Delta-X mission is a 5-year NASA Earth Venture Suborbital-3 mission to study the Mississippi River Delta in the United States, which is growing and sinking in different areas. River deltas and their wetlands are drowning as a result of sea level rise and reduced sediment inputs. The Delta-X mission will determine which parts will survive and continue to grow, and which parts will be lost. Delta-X begins with airborne and in situ data acquisition and carries through data analysis, model integration, and validation to predict the extent and spatial patterns of future deltaic land loss or gain.

Related datasets

Castaneda, E., A.I. Christensen, M. Simard, A. Bevington, R. Twilley, and A. Mccall. 2020. Pre-Delta-X: Vegetation Species, Structure, Aboveground Biomass, MRD, LA, USA, 2015. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1805

Related Publications

‌‌Thomas, N., M. Simard, E. Castañeda-Moya, K. Byrd, L. Windham-Myers, A. Bevington, and R.R. Twilley. 2019. High-resolution mapping of biomass and distribution of marsh and forested wetlands in southeastern coastal Louisiana. International Journal of Applied Earth Observation and Geoinformation, 80:257–267. https://doi.org/10.1016/j.jag.2019.03.013

Acknowledgement

This study was funded with the Earth Venture Suborbital (EVS-3) program, grant number NNH17ZDA001N-EVS3.

Data Characteristics

Spatial Coverage:  Atchafalaya and Terrebonne Basins, Mississippi River Delta (MRD) floodplain, southern coast of Louisiana, USA

Spatial Resolution: Points

Temporal Coverage: Spring: 2021-03-21 to 2021-03-31 and Fall: 2021-08-19 to 2021-08-27

Temporal Resolution: One-time measurements

Site Boundaries: Latitude and longitude are given in decimal degrees.

Site Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
Atchafalaya and Terrebonne Basins -91.8852 -90.82192 29.51 29.1714

Data File Information

There are two files in comma-separated values (.csv) format: DeltaX_VegetationStructure_Spring2021.csv and DeltaX_VegetationStructure_Fall2021.csv

Missing data or data not collected are reported as -9999 for numeric data and NA for missing text data.

Table 1. Variables in the data file.

Variable Units of measurement Description
basin   “Atchafalaya” or “Terrebonne”
campaign   Spring 2021 and Fall 2021
date YYYY-MM-DD Date collected
latitude degrees north Location of sampling site
longitude degrees east Location of sampling site
site_id   Site name
hydrogeomorphic_zone   Supratidal and Intertidal
sampling_station   Sampling station (Spring file only)
quarter_id   Sampling unit
dominant_species   Dominant species
vegetation_class   Aboveground biomass (AGB) or necromass (AGN)
number_stems_per_quarter   Number of stems measured in a quarter
mean_height cm Average height of plants within a quarter
mean_diameter mm Average diameter of plant stems within a quarter.
stem_density stems per m2 Number of plant stems per unit area

Application and Derivation

Vegetation structure measurements will be used to calibrate remote sensing data (e.g., UAVSAR, AVRIS) and hydrodynamic and sediment transport models. This research will contribute to a better understanding of how vegetation dynamics and zonation are likely to be influenced by changing ecosystems across deltaic basins. Additionally, the results of this study will be used to generate landscape-level vegetation mapping and patterns to identify indicators of ecosystem vulnerability across multiple coastal basins and environmental settings.

Quality Assessment

Structural attributes measured within plot quarters were averaged to estimate mean values and standard errors (± 1 SE) for all HGM zones across all sites.

Data Acquisition, Materials, and Methods

The Spring and Fall 2021 field deployments were conducted during March 19 – April 2 and August 19 – 27, 2021 across the Atchafalaya and Terrebonne basins in the Mississippi River Delta in coastal Louisiana. These data were collected to assess aboveground vegetation dynamics in response to seasonality, soil properties, and river discharge regimes (low vs. high) across different hydrogeomorphic (HGM) zones.These periods correspond to the early phase of the vegetation growing season and the peak of the spring river flood season, while August-September is considered the period of peak biomass and a period of low river discharge.The data cover the period 2021-03-21 to 2021-03-31 and 2021-08-19 to 2021-08-27.

Study Sites

Five out of the six selected sites for field measurements are part of the Coastal Reference Monitoring System (CRMS, Steyer et al., 2003) and are labeled with ‘CRMS’ in the csv file. The other site is in the Wax Lake Delta (WLD) without appropriate adjacent CRMS sites. Sites in both basins were chosen to represent a salinity gradient including freshwater, brackish, and saline ecosystems.
 

Study sites

Figure 2. Study site locations.

At each herbaceous wetland site, a transect was established perpendicular to the wetland edge to capture a range of hydrogeomorphic zones (supratidal and intertidal). In each hydrogeomorphic zone (HGM), two sampling stations were established 30 m apart (parallel to the wetland edge). For the herbaceous wetland sites, vegetation structure was measured and assessed in one plot (0.25 m2) in each sampling station for each HGM zone. Vegetation structure measurements included stem density (# stems m-2), stem height (cm), and stem diameter (mm). Stem density was calculated for all species by counting all individual plant stems within the plot. Due to the high density of stems per unit area, plots were divided into four quarters (area = 0.0625 m2) to measure the diameter and height of all individuals within one or two of four quarters at all sites, except at the supratidal zone in Mike Island, WLD during both campaigns. Here, we used a 1 m2 quadrat to measure and count all plant stems within the quadrat due to the low density of stems. Vegetation height and diameter were measured using a meter stick (1 mm resolution) and a digital caliper (0.01 mm resolution), respectively. In the lab, the aboveground plant material collected at all plots was initially sorted by species using standard field protocols.

 

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Delta-X: Aboveground Vegetation Structure for Herbaceous Wetlands across MRD, LA, USA

Contact for Data Center Access Information:

References

Steyer, G.D., C.E. Sasser, J.M. Visser, E.M., Swenson, J.A. Nyman, and R.C. Raynie. 2003. A proposed coast-wide reference monitoring system for evaluating wetland restoration trajectories in Louisiana. Environmental Monitoring and Assessment 81:107–117. https://doi.org/10.1023/A:1021368722681

‌‌Thomas, N., M. Simard, E. Castañeda-Moya, K. Byrd, L. Windham-Myers, A. Bevington, and R.R. Twilley. 2019. High-resolution mapping of biomass and distribution of marsh and forested wetlands in southeastern coastal Louisiana. International Journal of Applied Earth Observation and Geoinformation 80:257–267. https://doi.org/10.1016/j.jag.2019.03.013