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INTRODUCTION Historical accounts by travelers and explorers locate and describe prairie areas in Mississippi dating back to Hernando de Soto’s expedition in the sixteenth century (Rostlund 1957). The Mississippi Natural Heritage Program has identi¤ed and described more than 54 current prairie remnants in the Jackson Prairie region of Mississippi (Figure 9.1). They de¤ne the prairies as natural grasslands with predominantly native perennial grasses and some herbaceous plants (Gordon and Wiseman 1989). Prairies are considered closed communities with common ecological features such as the dominance of grasses, scarcity of shrubs and trees, presence of typical drought-enduring and largely disease-free vegetation, prevalence of vegetative reproduction, and rapid renewal of vegetative growth with plant longevity (Weaver 1968). Prairie soils are usually ¤ne-textured, productive, and fertile with high cation exchange capacity clays and weatherable minerals that serve as plant nutrient reserves. According to Hutchison (1994), early travelers in the Midwest characterized areas that were neither good prairie nor good forest as barrens . Barren vegetation was characterized as a mixture of both stunted trees and herbaceous species with the grasses occurring as clumps. Dead trees or trees with dead limbs were common and shrubby species typically formed thickets. The occurrence of barrens was often related to thin, bare soils with bedrock at or near the surface, and slopes facing south-southwest that provided more heat and less available moisture, conditions conducive to the development of dry forbs and grasses rather than trees. 9 Plant and Soil Interactions in Prairie Remnants of the Jackson Prairie Region, Mississippi L. P. Moran, D. E. Pettry, and R. E. Switzer The Jackson Prairie region in Mississippi consists of gently rolling uplands underlain by the Yazoo clay of the Jackson group. The Yazoo clay is a green to gray calcareous clay of Eocene age, high in montmorillonite and re®ective of near-shore marine deposition (Merrill et al. 1985). The prairie soils are commonly thick, alkaline, montmorillonitic Vertisols of high natural fertility. The prairies are calcareous islands surrounded by mixed acidic pine and hardwood forests on level to gently sloping upland positions (Moran 1995). The Jackson Prairie region has undergone intense settlement and cultivation that has greatly affected soil and vegetative conditions for the past 200 years. A large portion of this region is forested and contains more introduced species than in the past, re®ecting the extensive erosion after European settlement (cf. Peacock 1992, 1993 for the Mississippi Black Prairie). Characterizing and understanding present-day soil and vegetative interactions of the remaining remnants are crucial for successful management and conservation. Following a brief review Fig. 9.1. Location of Jackson Prairie study areas, south-central Mississippi. From Moran et al. (1997; Figure 1) Plant and Soil Interactions in Prairie Remnants 147 of vegetative characteristics and current management practices, we will discuss typical soil and plant relationships in prairie remnants in the Jackson Prairie region. NATURAL CHARACTERISTICS AND MANAGEMENT PRACTICE Graminoids (15 percent), composites (21 percent), and legumes (12 percent ) comprise the majority of plant species in the prairie remnants of the Jackson Prairie region (Wieland et al. 1991). The vegetation is similar to that of prairie species in the midwestern United States (Wieland 1991). Table 9.1 lists common species found in the Bienville National Forest in the Jackson Prairie region. Historical sources indicate that eastern prairies had low tree densities. Low tree-density areas (fewer than 25 trees ha−1 ) occurred on alkaline upland ¤ne-textured soils. High tree densities (more than 295 trees ha−1 ), on the other hand, occurred on acidic areas lying outside the low tree-density areas in the Mississippi Black Prairie (Jones and Patton 1966; Rankin and Davis 1971). Wieland and Weeks (1990) conducted a study of the soils and vegetation in the Jackson prairies, ¤nding pine trees on gentle, acidic slopes and tall grasses on sloping, alkaline sites. Burning is one of the most signi¤cant ecological management tools for prairie openings. Fire reduces tree and shrub competition. Fire also increases aboveground plant production in prairie ecosystems by releasing available nitrogen and phosphorus, increasing nitrogen mineralization rates, enhancing nitrogen ¤xation, and altering microclimatic soil and plant conditions. Short-term effects of ¤re include increased soil temperature and light exposure and decreased soil moisture (Ojima et al. 1990; Old 1969). Long-term effects include decreasing soil organic matter, modifying vegetative composition, and maintaining productivity despite the loss of labile organic matter (Ojima et al. 1990). Frost et al. (1986) cited ¤re frequency and depth of the...

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