William Conner, Ph.D. - Research & Projects

Ecology and Management of Forested Wetland Ecosystems of the Southern United States

Summary

Forested wetlands have been an influential component of the economy and culture of the southern United States since the earliest settlements. These ecosystems have been used for transportation, food and fiber, flood control, wildlife habitat, recreation, and all too often, a fertile site for conversion to agriculture. The importance of wetlands to the southern economy and concern over their decreasing extent has lead to a surge of research activity as well as litigation and discord over competing wetland uses. Hydrology is one of the most important driving forces in forested wetlands, and the length, depth, and timing of flooding determines the diversity and productivity of these systems. Changes in normal hydrology patterns due to stream channelization or construction of roads, canals, levees, or dams affect the establishment and growth of forest species. Another aspect of hydrology that needs consideration, especially in coastal areas, is eustatic sea level rise and subsidence. The long-term impacts of disturbance is a major area of research in Dr. Conner’s program.  Only long-term research can consider both the short- and long-term fluctuations of key driving forces. In addition, Dr. Conner is examining processes across the entire southern United States to determine if all wetlands function similarly.


Projects

Climate Change and Tidally Influenced Freshwater Forested Wetlands of the Southeast: Understanding Functional Ecological Attributes of Forest Transitions to Marsh (2009-2014), USGS – GCC funding, William Conner (Clemson University)
Tidal freshwater forested wetlands are unique ecosystems that provide an opportunity for understanding the unique structuring of freshwater forests along hydroperiod, salinity, and microtopographical gradients. The goal of this project is to take a regional approach in studying community dynamics of tidal freshwater forested wetlands to understand the ecology and potential effects of sea-level rise on this ecosystem. Study plots were established in a previous GCC project (Dieback and Restoration of Coastal Forests of the Southeast Under Changing Climate; Interactive Effects of Drought Severity, Hurricanes, Sea-Level Rise and Coastal Management) in tidal freshwater swamps with varying tidal influence in riverine and non-riverine watersheds in coastal South Carolina. Plots extended from healthy to stressed cypress-tupelo communities and consisted of cypress stands located along a transect gradient from fresh to brackish environments. Monthly field trips are made to the sites to collect tree growth, litterfall, water level, and soil salinity data. Further, additional data regarding microhabitat use and availability will be collected, and distinct strategies of species preference for microsite will be elucidated through dedicated whole-tree eco-physiological studies. This study will increase our understanding of tidal freshwater forested wetlands at the regional level, thereby providing a better base of knowledge from which future management goals can draw. A broad understanding of community composition, their associations with soil and hydrology, and usage of microtopography will help direct future restoration and mitigation efforts. Learning the physiology associated with water transport in trees under differing environmental conditions will allow us to understand the specific physiological requirements of trees at different microtopographic and landscape positions. This knowledge, in turn, will help balance municipal river-water use with environmental responses to flow management. These advancements will increase our ability to sustain ecosystem health, conserve and preserve wildlife, and minimize relative sea-level rise by enhancing long-term carbon sequestration. photo of tree canopy on Butler Island opening up as salinity levels incraese and marsh grasses are starting to take over
Understanding relationships between sediment and carbon deposition and floodplain forest functions in the Congaree National Park, SC (2010-2013), USGS funding, William Conner (Clemson University), Graeme Lockaby (Auburn University), and Cliff Hupp (USGS)
Given the expectation of increased land use disturbances within watersheds throughout the world and the high potential for increased sediment generation as a result, it is critical that we determine how floodplain forests and associated functions may be altered. Consequently, sustainability of floodplain forests will depend on understanding relationships among land use change, sediment loads in streams, channel-floodplain connectivity, and floodplain forest integrity within key river basins. The Congaree National Park (CNP) represents one of the very few old-growth floodplain forests still in existence, thus making it an ideal setting for this investigation. Sediment deposition and distribution on the CNP floodplain control both aboveground net primary productivity (ANPP) and species composition of that system. The objectives of this study are to (1) determine the extent to which current and past sedimentation rates vary among different wetland vegetation communities, (2) determine how carbon sequestration varies in association with sedimentation differences among communities, and (3) examine the nature of relationships that exist between past and current aboveground net primary productivity, species composition, and sedimentation rates. Detailed analyses will be conducted along 5 transects established going from the highest elevation (natural levee) to the lowest (cypress/tupelo swamp). Studies are examining the effects of sedimentation on floodplain forest composition and productivity as well as nutrient dynamics. Photo of Dr. Conner in Congaree forest