13 Terrestrial Wetlands

The objective of this chapter is to characterize the distribution of carbon stocks and fluxes in terrestrial wetlands within North America. The approach was to synthesize available literature from field measurements with analyses of resource inventory data to estimate wetland area, carbon stocks, and net ecosystem exchange (NEE) of carbon and methane (CH4) fluxes of terrestrial wetlands (see Appendices 13A, p. 547, and 13B, p. 557, for details1). Then, the findings employed from large-scale simulation studies provided additional context, with consideration given to the effects of disturbance regimes, restoration and creation of terrestrial wetlands, and the application of modeling tools to assess the carbon cycle of terrestrial wetlands

Long-Term Ecohydrologic Monitoring: A Case Study from the Santee Experimental Forest, South Carolina

Long-term research on gauged watersheds within the USDA Forest Service’s Experimental Forest and Range (EFR) network has contributed substantially to our understanding of relationships among forests, water, and hydrologic processes and watershed management, yet there is only limited information from coastal forests. This article summarizes key findings from hydrology and water-quality studies based on long-term monitoring on first-, second-, and third-order watersheds on the Santee Experimental Forest, which are a part of the headwaters of the east branch of the Cooper River that drains into the harbor of Charleston, South Carolina. The watersheds are representative forest ecosystems that are characteristic of the low-gradient Atlantic Coastal Plain. The long-term (35-year) water balance shows an average annual runoff of 22% of the precipitation and an estimated 75% for the evapotranspiration (ET), leaving the balance to groundwater. Non-growing season prescribed fire, an operational management practice, shows no effects on streamflow and nutrient export. The long-term records were fundamental to understanding the effects of Hurricane Hugo in 1989 on the water balance of the paired watersheds that were related to vegetation damage by Hugo and post-Hugo responses of vegetation. The long-term precipitation records showed that the frequency of large rainfall events has increased over the last two decades. Although there was an increase in air temperature, there was no effect of that increase on annual streamflow and water table depths. The long-term watershed records provide information needed to improve design, planning, and assessment methods and tools used for addressing the potential impacts of hydrologic responses on extreme events; risk and vulnerability assessments of land use; and climate and forest disturbance on hydrology, ecology, biogeochemistry, and water supply

Hydrologic Influences Within a Tidal Freshwater Forested Wetland

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen

Comparison of Potential Evapotranspiration (PET) using Three Methods for a Grass Reference and a Natural Forest in Coastal Plain of South Carolina

2014 S.C. Water Resources Conference - Informing Strategic Water Planning to Address Natural Resource, Community and Economic Challenge

Assessment of the Reach and Ecological Condition of Freshwater Tidal Creeks in the Lower Coastal Plain, Charleston County, South Carolina with Advanced Geospatial Technology Application

Tidal freshwater wetlands are the interface between marine and terrestrial ecosystems; hence they are directly impacted by sea level rise and climate change (James & Callahan, 2012). Little is known about the hydro-ecological functions and ecosystem services provided by these important and widely-distributed ecosystems. These wetlands are common in the urbanizing landscape of the southeastern Atlantic coastal plain, as well as other coastal areas. Tidal fresh-water forested wetlands (TFFW) occur in floodplains situated near the coastal zone along freshwater rivers that are subject to tides. They are most prominent along the Southeastern Atlantic lower Coastal Plain, where it is estimated that 200,000 ha of TFFW exist. The majority of TFFW are concentrated along the coasts of the South Carolina, Georgia, Florida, Virginia and Maryland, with other areas along the Gulf coast and upper portions of the Atlantic Coastal Plain. South Carolina is considered to have the most land area, over 40,000 ha, due to the relatively large tide range and low topographic gradient. There is considerable uncertainty in the estimates of TFFW area, and inconsistent use of terminology complicates assessments of the resource

Soil Carbon within the Mangrove Landscape in Rufiji River Delta, Tanzania

Mangroves are among the most carbon-rich terrestrial ecosystems, primarily attributable to the soil pool. There are substantial differences in soil carbon (C) and nitrogen (N) due to the disparities in geomorphic settings and ecological drivers, but this insight is drawn primarily from observational studies. An objective inventory of carbon stocks in mangroves of the Rufiji River Delta, Tanzania was conducted. Seventy-five soil cores were collected within a 12,164 ha inventory area, comprising the northern portion of the delta. Cores were collected from intact and dwarf mangroves, agricultural fields, and mudflats. The spatial mean soil organic carbon (SOC) density in mangroves was 16.35 ± 6.25 mg C cm−3. Mean SOC density in non-vegetated mudflats was 12.16 ± 4.57 mg C cm−3, demonstrating that mangroves develop on soils with a substantial soil C stock. However, long-established mangroves had had a higher C density (17.27 ± 5.87 mg C cm−3). Using a δ13C mixing model, the source of soil organic matter in mudflats was primarily marine, while long-established mangroves was predominantly mangrove. There were small differences in SOC among long-established mangrove sites in different geomorphic settings. The proportion of marine-sourced SOC increased with soil depth in mangroves. The SOC and nitrogen of agricultural sites resemble those of mudflats, suggesting those sites are developed from relatively young forests. The SOC and nitrogen density in dwarf mangrove sites were lower than others, perhaps reflecting past disturbances

Runoff Generation from Shallow Water Table Southeastern Forested Watersheds: Unusual Behavior of Paired Watersheds Following Major Disturbance

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen

Estimating mangrove aboveground biomass from airborne LiDAR data: a case study from the Zambezi River delta

Mangroves are ecologically and economically important forested wetlands with the highest carbon (C) density of all terrestrial ecosystems. Because of their exceptionally large C stocks and importance as a coastal buffer, their protection and restoration has been proposed as effective mitigation strategy for climate change. The inclusion of mangroves in mitigation strategies requires the quantification of C stocks (both above and belowground) and changes to accurately calculate emissions and sequestration. A growing number of countries are becoming interested in using mitigation initiatives, such as REDD+, in these unique coastal forests. However, it is not yet clear how methods to measure C traditionally used for other ecosystems can be modified to estimate biomass in mangroves with the precision and accuracy needed for these initiatives. Airborne lidar (ALS) data has often been proposed as the most accurate way for larger-scale assessments but, the application of ALS for coastal wetlands is scarce, primarily due to a lack of contemporaneous ALS and field measurements. Here, we evaluated the variability in field and lidar-based estimates of aboveground biomass (AGB) through the combination of different local and regional allometric models and standardized height metrics that are comparable across spatial resolutions and sensor types. The end result being a simplified approach for accurately estimating mangrove AGB at large-scales and determining the uncertainty by combining multiple allometric models. We then quantified wall-to-wall aboveground biomass stocks of a tall mangrove forest in the Zambezi Delta, Mozambique. Our results indicate that the Lidar H100 height metric correlates well with AGB estimates, with R2 between 0.80 and 0.88 and RMSE of 33% or less. When comparing lidar H100 AGB derived from three allometric models, mean AGB values range from 192 Mg. ha-1 up to 252 Mg. ha-1. We suggest the best model to predict AGB was based on the East Africa specific allometry and a power based regression that used Lidar H100 as the height input with a R2 of 0.85 and a RMSE of 122 Mg.ha-1 or 33%. The total AGB of the lidar inventoried mangrove area (6654 ha) was 1,350,902 Mg with a mean AGB 203 Mg. ha-1. Because the allometry suggested here was developed using standardized height metrics, it is recommended that the models can generate AGB estimates using other remote sensing instruments that are more readily accessible over other mangrove ecosystems on a large scale, and as part of future carbon monitoring efforts in mangroves

Modeling the Effect of Land Use Change on Hydrology of a Forested Watershed in Coastal South Carolina

2008 S.C. Water Resources Conference - Addressing Water Challenges Facing the State and Regio