By 1980, the United States had lost over 50 percent of its original wetland resources. The U.S. National Wetland Inventory estimates that 95 percent of annual wetland losses since 1955 occurred to palustrine wetlands. The majority of these losses occurred to the three types of palustrine vegetated wetlands: emergent, forested, and shrub. The primary cause for wetland losses from the mid-1950s to the mid-1980s was agricultural conversion supported by federal agricultural policies, especially the Agricultural Conservation Program that provided significant direct and indirect support for wetland conversions. The rate of converting wetland to agriculture has declined since the mid-1950's with a significant decrease occurring between the mid-1970s and mid-1990s. Statistical analysis using correlation, regression and principal component analysis was performed to identify the major contributory factors in loss rates in the Midwest, Lower Mississippi River Valley and the Southeast United States. The variables considered are: Swampbuster provisions of the Food and Security Act of 1985, Conservation Reserve Program enrolled acreage and rental rates, Wetland Reserve Program and The Clean Water Act Section 404 permits; prices of corn, soybeans and wheat; and the percent of wetlands remaining. The results indicated agricultural policies and Clean Water Act Section 404 permits and wetland loss rates were negatively correlated and prices of corn, soybeans and wheat were positively correlated. The percentage of wetlands remaining, were also positively correlated with loss rates. Taken together, the selected agricultural policies, Section 404 permits, commodity prices and percent of wetland remaining, explain 96 percent of the variance in wetland loss rates and 94 percent of the agricultural losses nationally. These results are consistent, with minor variations, across geographic wetland strata and wetland types. Regional differences exist in the major type of wetland losses; emergent wetland losses were more prevalent in the agricultural Midwest, with forested wetland losses concentrated in the Lower Mississippi River Valley and the Southeast United States. The results of this research reflect the intricate relationships between federal legislation, regulatory programs, legal decisions, economic factors, and changes in society's view and understanding of the importance of wetlands and the need to merge conservation programs with agricultural policies. Economic factors exert a significant impact in decision-making of whether to convert or conserve wetland resources. The economic feasibility of installing drainage system to make wetlands farmable depends upon the relationship of capital investment cost and crop prices. Commodity prices impact decisions regarding enrollment into the Conservation Reserve Program and the Wetland Reserve Program; higher commodity prices can make conversion more profitable but low crop prices will make these programs more appealing economically. The Swampbuster provisions are effective in conserving wetlands if the economic penalties are significant to the individual farmer. The policy, legal and commodity variables were used to create models that explain the inter-relationship between agricultural economic factors, policy impacts and commodity prices. The models indicate how the variables could affect decision-making in determining whether to convert or conserve palustrine vegetated wetlands; increased commodity prices coupled with lower conservation program payments could jeopardize wetland conservation efforts and result in increased wetland loss rates due to increased wetland drainage and conversion.

Interest in, and rates of, wetland restoration have increased over the past several decades. However, despite proliferations of restored wetlands across the landscape, the structural and functional restoration success of these systems is unclear. Thus, understanding factors and processes that influence wetland characteristics is of considerable interest. This study focuses on herbaceous wetlands in the Mississippi River Alluvial Valley (MAV), a largely agricultural region interspersed with restored and naturally occurring wetlands. Chapter I is an introduction and provides a background to wetlands, wetland ecology, and the current state of wetland restoration in the United States. Chapter II focuses on factors which affect seedling density and similarities between standing vegetation, germinated seedlings, and early successional stage assemblages. Seedling density was heavily influenced by hydrology while richness and diversity were similar between restored and non-managed wetlands. Landscape-level factors affected seedling density, while germinated seedlings did not reflect standing vegetation in MAV wetlands. In Chapter III, I examine the impact of agricultural stressors on wetland plant assemblage development. Resulting assemblages showed strong fidelity to wetland soil site of origin while richness and diversity were negatively affected by elevated stressor levels. In Chapter IV, I compare characteristics between non-managed and restored wetlands in the MAV. These wetlands differed hydrologically, had different levels of soil organic matter, were dissimilar in plant assemblage composition, and varied by surrounding land use/cover. Finally, Chapter V is a discussion of the results and places this work within a larger context.