Ecological Research

Complex biotic and abiotic processes govern interactions between vegetation, soil, hydrology and fauna in wetland ecosystems. Vegetation is a major biological component of forested wetlands, influencing many aspects of ecosystem structure, function, and sustainable productivity. It is also the primary target of most management activities. Therefore, the ability to predict vegetation responses to disturbance and the consequent effects on wetland functions is central to developing useful guidelines for management and conservation.

Past studies of ecological processes and functions of forested wetlands are few compared to the diversity of conditions and information needs. There is limited basic information about the physiology of major wetland tree species, the structure and dynamics of pure and mixed species communities, soil-plant interactions, hydrology, soils, wildlife habitat, and primary biotic and abiotic functions. Existing information is often not in a form that can be applied to ecosystem problems, especially those related to management, restoration, or creation of forested wetlands. Accordingly, there is a critical need for research on fundamental biotic and abiotic processes and functions in forested wetland landscapes.

Staffs of the Center employ a combination of ecosystem characterization, field and controlled environment experimentation, and modeling to provide information needed to more effectively manage and conserve forested wetlands.

A synopsis of ecological research at the Center:

Ecological reference standards are used as a framework with which declines or recovery of ecological functions can be compared. In developing these standards, representative non-degraded ecosystems must be identified and their structure and processes must be thoroughly quantified as the basis for comparison. Complete ecological profiles for reference wetlands are being quantified. The ecosystems profiled include red- and black-river bottomland hardwood forests, Carolina Bays, pocosins, pine flatwoods, and mixed pine hardwoods.

These field research projects include long-term studies of structure and function using biotic and abiotic assessments. Topics include geomorphology; hydrology; soils; vegetation dynamics; above- and below-ground primary productivity, mortality and decomposition; coarse woody debris dynamics; nutrient cycling; water quality; sedimentation; avian populations; and microbial ecology. Research sites include the Coosawhatchie Bottomland Ecosystem Study (CBES) site, the Savannah River Site (SRS), and pocosins in Dare County .

Indicators of forest health are being developed based on field studies, experiments, and published literature. From this information, models are being developed to synthesize ecological processes, structure, and functions of bottomland hardwood forests.

The function of root processes in wetland hardwood forest health is being evaluated and the contributions of root production to forest productivity are being documented. Belowground primary productivity, mortality, decomposition, the phenology of growth, and the dynamics of length and surface area, and mycorrhizal relationships are being studied and contrasted among wetland communities. In addition, the conversion of plant litter to soil organic matter along hydrologic and successional gradients, and carbon and nitrogen mineralization dynamics along hydrologic gradients are being studied. Research sites include the CBES and SRS.

How environmental factors (hydrology, light, and competitive interactions) and land use (agricultural activity, logging history, changes in hydrology, and restoration practices employed) contribute to community composition and dynamics in unmanaged bottomland hardwood, mixed pine-hardwoods, wet pine forests, Carolina bays and pocosins is being determined. These studies are of plant community regeneration and canopy gap dynamics, and will be used in models that predict: 1) growth responses of major wetland forest tree species to competition and environmental factors and 2) wildlife habitat (forest structure) responses to these biotic and abiotic factors. Research sites include the CBES, SRS, and Dare County.

The Role of Hurricanes in Strucuring Forest Vegetation
Disturbances, whether natural such as fire and hurricane, or human such as silvicultural thinnings or regeneration cuts, have a significant effect on forest development since they damage vegetation and release growing space for other species. Hurricane Hugo (September, 1989) provided a significant opportunity to study the role of disturbances in determining forest structure and species composition.

A cooperative research project supported by the Andrew W. Mellon Foundation was established between Clemson University , The University of Georgia, The National Audubon Society, and the CFWR to establish and monitor a series of plots in the hurricane-devastated area of South Carolina . Permanent plots were established in formerly mature natural stands of five forest cover types including: cypress-tupelo swamps, bottomland hardwoods, pine-hardwoods, upland hardwoods, and longleaf pine. Selected vegetation and site factors are being measured at intervals and periodically evaluated and published in status reports.

Two of the permanent plots are located within the boundaries of Watershed 80 on the Santee Experimental Forest . The watershed is one of three gauged watersheds on the experimental forest; a weather station is also located on each of the watersheds.

Response of a forest community to hurricane - fire interactions.
A long-term monitoring study was established on the Santee Experimental Forest in cooperation with Clemson University to investigate the manner in which fire influences plant community development after a hurricane. Initial post-hurricane prescribed fire treatments, conducted during the dormant and growing-seasons two years after Hurricane Hugo, will be followed by fire reapplied at frequent and infrequent intervals.

These types of studies are being conducted on the Santee Experimental Forest and other forests in the path of hurricane Hugo, and at Dare County.

Traits related to high productivity for wetland tree species grown on different site types are being identified. Greenhouse experiments are being conducted to evaluate performance of fast growing bottomland hardwood species and to test the influence of hydroperiod on survival, above-and below-ground production, carbon allocation to structural and non-structural components, root adaptations to hypoxia, gas exchange, nutrient uptake, and nutrient cycling. These studies are being conducted in Charleston and at the SRS.

We are conducting field experiments in pine and hardwood stands supplied with a range of water and nutrient resources to evaluate processes controlling productivity. Our main interest is in resource capture including light interception, water requirements and nutrient uptake. The main drivers of productivity are expected to be leaf area development and the amount of light absorbed by the canopy. Soil resource availability and allocation of nutrients among above and belowground tissues will modify the level of light-driven production. To evaluate changes in allocation, we are monitoring nutrient mass balance among the various tissues through periodic harvests. We are using the information gathered, including climate and soil conditions, to test predictive models of forest productivity.

About Us: Managed Forested Wetlands: Ecological Research