Academic journal article The American Midland Naturalist

Soil Quality Differences under Native Tallgrass Prairie across a Climosequence in Arkansas

Academic journal article The American Midland Naturalist

Soil Quality Differences under Native Tallgrass Prairie across a Climosequence in Arkansas

Article excerpt

ABSIRACT.-

Climate, specifically moisture and temperature, influences plant growth and nutrient cycling; thns, climate also influences prairie development. Relatively little research has been conducted in the ecological transition zone between the Great Plains and the more humid forests. Since moisture and temperature affect many ecosystem processes, the wetter climate of the southern forest region should influence soil biogeochemical cycling" quite differently from that in grassland soils. The objective of this study was to evaluate soil quality and the relationships between selected soil properties across a climosequence in a transition zone between tallgrass prairie in humid-temperate (Ozark Highlands) and humid-subtropical (Grand Prairie) climate regimes in Arkansas. Soil physical, chemical and biological properties of the upper 10 cm differed significantly between physiographic regions. Linear relationships between total soil nitrogen (N) and carbon (C), extractable phosphorus and manganese, electrical conductivity and soil organic matter concentration differed significantly between physiographic regions. Total soil N and C decreased with increasing soil bulk density in both physiographic regions. The relationship between total C and bulk density differed by physiographic region, while the relationship between total N and bulk density did not. Soil organic matter concentration, C:N ratio, and many extractable nutrients, were higher and relationships between selected soil properties differed under native tallgrass prairie in a relatively warm and wet climate than that in a relatively cooler and drier climate. The results of this study suggest that prairie preservation, restoration and management practices should dilfer depending on climate regimes.

INTRODUCTION

Prairies originally occupied vast expanses of the North American Great Plains, stretching from Canada to Mexico and from the Rocky Mountains to western Indiana. Tallgrass prairies were interspersed with forest vegetation in the humid central U.S. with grasslands occurring as smaller and more disjointed patches from west to east along an increasing rainfall gradient. European settlement and agricultural exploitation have caused nearly complete loss of native prairies, especially the tallgrass prairies in the humid zones (Sampson and Knopf, 1994).

As a consequence, prairie preservation and restoration are needed to arrest the loss of plant species diversity and wildlife habitat and to retain environmentally beneficial soil functions. Native prairie soils are high in organic matter content and promote infiltration and storage of water and sequestration of atmospheric carbon (C) and nitrogen (N). Native prairie patches in the humid zone, while rare, can provide benchmark soil data on physical, chemical and biological properties to guide ecosystem restoration projects. However, information is lacking on the characteristics of prairie soils that developed under humid conditions and on the climatic factors that influenced prairie development in forested zones.

Native prairie occurrence was favored by limited soil water availability and relatively high evaporative demand during the growing season in conjunction with disturbances, such as fire, to reduce woody encroachment (West and Nelson, 2003). The western edge of the Ozark Highlands in northeast Oklahoma and northwest Arkansas is a transition zone from the Great Plains to the west to the more humid forestlands to the east. Since moisture and temperature affect many ecosystem processes, the wetter climate of the southern forest region likely influences soil biogeochemical cycling differently from that in grassland soils in the Great Plains. Specifically, responses to climatic conditions are expected for the turnover of C (McDaniel and Munn, 1985; Burke et al, 1989; Stevenson and Cole, 1999), N (Jenny, 1930; Stevenson and Cole, 1999), organic matter (Jenny, 1930; Haas et al, 1957; Honeycutt et al, 1990; Stevenson and Cole, 1999), other soil nutrients (Stevenson and Cole, 1999) and for net primary productivity (Sala et al, 1988). …

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