These methods, instrumentation and/or protocols apply to all data in this dataset:| Methods and protocols used in the collection of this data package |
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Sampling design
Soil core sample point allocation was done through a process of random point allocation with special attention paid to areas across the sites with distinct vegetation differences.
Zone 1 – Aumann Reference/Remnant Prairie (Parade Ground) – 91.7 acres, 32 points (1 per 2.9 ac)
Zone 2 – Southwest Prairie Remnant Prairie – 24.3 acres, 9 points (1 per 2.7 ac)
Zone 3 – South Central Prairie Remnant Prairie – 48.4 acres, 17 points (1 per 2.8 ac)
Zone 4 – Tallow Sprayed Areas – 38.0 acres, 13 points (1 per 2.9 ac)
Zone 5 – Tallow Shredded Areas – 2.5 acres, 2 points (1 per 1.3 ac)
Zone 6 – Tallow Treatment Priority – 12.2 acres, 4 points (1 per 3.1 ac)
Zone 7 – Deer Park Reference/Remnant Prairie – 53.6 acres, 15 points (1 per 3.57ac)
These distinct areas were identified due to their different management practices and history and the intent to evaluate these areas within the larger UHCC site for their potentially different rates of carbon accrual. All sample point locations were then randomly generated with ArcGIS for each of those distinct areas. A total of 92 soil sample locations were allocated across the distinct areas based on the acreage of each. The target soil sample to acreage ratio was approximately 1 sample per 2.5 acres, but this was not always possible due to site conditions.
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Soil Carbon Sampling
During the week of October 10, 2022, a team of two RES field ecologists completed the soil carbon sampling on both the UHCC site and the Deer Park Prairie Preserve. After meeting with interested parties, the crew then deployed to the nearest point utilizing the ESRI Collector application with a sub-meter-accuracy Trimble R1 GPS unit. This ensures precision of sample collection and allows for revisiting and resampling the same points in future years. Once a plan for sampling the points was in place, the crew navigated to each of the points with a Polaris Ranger 6x6 and completed soil sampling with a bed mounted Giddings hydraulic soil sampler. Once at each pre-determined sample point, the crew collected and labeled the soil core, then marked the actual collection point on the Collector application. Each core was taken down to 1m depth or less, in the event an impenetrable layer was reached. In total, ninety-two (92) soil cores were collected from the UHCC site and the Deer Park Prairie Preserve. These samples were analyzed by Cquester Analytics for bulk density and soil carbon concentration over the winter months. Rocks and roots were sieved out of samples before analysis.
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Vegetation Sampling
During the week of October 10, 2022, a RES ecologist with a specialty in botany completed the vegetation sampling at each of the 92 sample locations. At each location, both a soil sample and a vegetation sample were taken. The soil sample was geolocated and the vegetation samples were taken in the immediate vicinity. Due to the timing of the sampling (late in the growing season), an additional visit was completed during late spring 2023 to capture a fuller picture of species diversity.
The vegetation composition sampling included measuring the cover and frequency of each plant species identified within a one square-meter (1m2) quadrat, as well as other non-vegetative cover types such as fine litter, bare soil, and rock. A total of 92 quadrats were randomly allocated across the UHCC site and the Deer Park Reference Prairie. Upon arrival at each sample point, the botanist recorded the plant species present and their respective cover values and the non-vegetation cover. At each sample point, vegetation by plant species was ocularly estimated to the nearest 5% based on vertically projected photosynthetic cover in a one-meter circular quadrat centered over each sample point. The vegetative cover from both the 2022 and 2023 surveys were combined to calculate vegetation metrics.
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Soil Data Analysis
Raw data for soil carbon were obtained as organic (SOC), inorganic, and total carbon concentration (%) values broken into soil depth increments: 0-15cm, 15-30cm, 30-50cm, and 50-100cm. Bulk density was provided with the carbon data for each depth increment in each core, allowing the calculation of the soil carbon stocks (in metric tonnes/hectare) of both fractions (organic and inorganic) for each depth increment. For each soil core, the sum of carbon stocks for all depth increments was calculated, and the mean and standard error were calculated for each unit.
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Floristic Quality Index
The Floristic Quality Index (FQI) was developed by Swink and Wilhelm (1994) to provide a simple numerical index of site quality that could be used to make comparisons across sites. The main value of importance in the index is the Coefficient of Conservatism, commonly called the C value. C values range from 0 to 10 and, in a very rough sense, indicate the dependence of the given species on either highly disturbed (0) or very mature remnant (10) sites. There are some scientists who employ values below 0 for non-native invasive species but the more common practice, which was used in this study, is to assign a value of 0 to all non-native species. The C values for individual plant species are assigned either by a known botanist with expertise to assess them or by a panel of several botanists.
This method of site assessment is highly developed in the Chicago region, largely due to buy-in and guidance from the Chicago District US Army Corps of Engineers. Because the C values for each species will differ significantly in different regions, other areas of the country have begun to develop C values. Gulf coastal prairies have, fortunately, had some attention in this respect, but official guidance is limited. Ideally, a comprehensive list of C values specific to Texas gulf coast prairies would be used, but we were unable to locate one. However, an assessment of coastal prairies was made in Louisiana by the US Army Corps of Engineers (Suir and Sasser 2017). For the current assessment, a similar methodology was followed regarding assigning C values: values assigned by Cretini, et al. (2012) were prioritized as having the highest relevance. If a species did not have a value assigned, values from Allain, et al. (2004), Gianopulos (2014), or Reemts & Eidson (2019) were used, in order of preference based on relevance. The breakdown of sources was: 54% were taken from Cretini, et al., 31% from Allain, et al., 4% from Gianopulos, and 9% from Reemts & Eidson. C values for 2% of species could not be found within the given lists. The source for each value is listed on a per-species basis in the Plant List.
Allain, Larry, Latimore Smith, Charles Allen, Malcolm F. Vidrine, and James B. Grace. 2004. "A Floristic Quality Assessment System for the Coastal Prairie of Louisiana." Proceedings of the North American Prairie Conferences. Lincoln, Nebraska: University of Nebraska - Lincoln.
Cretini, Kari F., Jenneke M. Visser, Ken W. Krauss, and Gregory D. Steyer. 2012. "Development and use of a floristic quality index for coastal Louisiana marshes." Environmental Monitoring and Assessment 2389–2403.
Gianopulos, Kristie. 2014. Coefficient of Conservatism Database Development for Wetland Plants Occurring in the Southeast United States. Report to the EPA, Region 4, North Carolina Dept. of Environment & Natural Resources, Division of Water Resources: Wetlands Branch.
Reemts, C. M., and J. A. Eidson. 2019. "Choosing Plant Diversity Metrics: A Tallgrass Prairie Case Study." Ecological Restoration 233-245.
Suir, Glenn M., and Charles E. Sasser. 2017. Floristic Quality Index of Restored Wetlands in Coastal Louisiana. Washington, DC: U.S. Army Corps of Engineers.
Swink, Frank, and Gerould Wilhelm. 1994. Plants of the Chicago Region. 4th Edition. Indianapolis, Indiana: Indiana Academy of Science.
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