LAND-USE AND ENVIRONMENTAL-FACTORS INFLUENCING SOIL SURFACE CO2 FLUX AND MICROBIAL BIOMASS IN NATURAL AND MANAGED ECOSYSTEMS IN SOUTHERN WISCONSIN

Many of the native prairies in southern Wisconsin, and the midwestern United States in general, have been replaced by conventional tilt (chi sel plow) and no-tillage corn agroecosystems. However, knowledge of th e influence of land use change on the structure and function of ecosys tems is incomplete. Soil surface CO2 flux is a major transfer of carbo n from terrestrial ecosystems to the atmosphere and varies greatly amo ng vegetation types. We measured soil surface CO2 flux and microbial b iomass in tilled and no-till corn agroecosystems and a restored prairi e ecosystem, examined the influence of various environmental factors o n soil surface CO2 flux in these ecosystems, and estimated annual soil surface CO2 flux for the natural and managed ecosystems. Soil surface CO2 flux is significantly greater for prairie and conventional tilled corn than for no-till corn in the spring, greater for prairie than ti lled and no-till corn from July to early October, and is similar for a ll three ecosystems in the late fall and winter. Soil surface CO2 flux is positively correlated to soil temperature at 10 cm for all three e cosystems (r(2) = 0.43-0.60, P < 0.001), but is only weakly correlated to soil moisture. Using an empirical model to estimate soil surface C O2 flux from 10 cm soil temperatures, we estimate annual soil surface CO2 fluxes of 508, 535 and 719 (g C m(-2) y(-1)) for the tilled and no -till corn and restored prairie ecosystems, respectively, demonstratin g that land use practices significantly affect soil surface CO2 flux. (C) 1998 Elsevier Science Ltd. All rights reserved.