Dissolved Organic Carbon Concentrations in Soil Water Collected in Tully Soils from a Tallgrass Prairie

Abstract

Dissolved organic carbon (DOC) from soil water was monitored in a tallgrass prairie using porous cup lysimeters positioned at two depths (20 and 80 cm) in Tully soils on six watersheds representing two different burn treatments and a control. In 1983, DOC averaged 31.8 ? 2.5 (SE) mg/liter and ranged from 1.1 to 169.5 mg/liter. DOC was lower in 1984, averaged 4.6 + 0.3 (SE) mg/liter and ranged from 1.4 to 22.8 mg/liter. Mean DOC concentration at the 20 cm and 80 cm depths across six watersheds were similar during 1983 but differed in 1984 with higher DOC concentrations occurring at the 20 cm depth. Depth comparisons within watersheds for samples taken in 1983 indicated that soil profile depth did not significantly affect DOC concentrations. In 1984, three of six watersheds had significantly higher levels of DOC at the 20 cm depth. During 1983, a seasonal effect in DOC concentrations was observed on four of five watersheds. Low DOC concentrations occurred early in the year, peaked in June and July, and declined thereafter. In 1984, seasonal fluctuations were not evident, possibly reflecting restricted sampling dates. Mean comparisons during 1983 between annual burned, 4-year burned, and unburned sites indicated that annual burned sites had lower DOC levels than unburned sites. In 1984, differences resulting from burn regimes were not apparent. Results suggest that many factors acting independently or synergistically influence DOC concentrations, reflecting the complexity of DOC dynamics in the tallgrass prairie. The relationships among fire frequency, plant species composition, and productivity in prairie ecosystems have been extensively documented (Robocker and Miller, 1955; Kucera and Ehrenreich, 1962; Hadley and Kieckhefer, 1963; Hulbert, 1969; Rice and Parenti, 1978; Seastedt, 1985). Some effort has been directed toward understanding organic nitrogen cycles in ' Present address: Florida Game and Fresh Water Fish Commission, Route 7, Box 440, Lake City, Florida 32055. This content downloaded from 157.55.39.113 on Wed, 05 Jul 2017 18:07:41 UTC All use subject to http://about.jstor.org/terms 122 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE prairie ecosystems (Bokhari and Singh, 1975; Woodmansee, 1978; Risser and Parton, 1982; Seastedt and Hayes, 1988), but other aspects of soil solution chemistry are less known. The objectives of this study were to: 1) provide baseline data on dissolved organic carbon (DOC) concentrations in soil water collected from Tully soils in native prairie, and 2) examine the influence of soil profile depth, season, and fire frequency on DOC concentrations.