Long-Term Effects of Mechanical Renovation of a Mixed-Grass Prairie: II. Carbon and Nitrogen Balance

Abstract

In 1979, a study was initiated on the northern mixed-grass prairie of southeastern Wyoming USA to determine the effects of mechanical rangeland renovation (ripping and double ripping) on forage production. Mechanical treatments resulted in increased forage production and higher livestock carrying capacities. The original study plots were evaluated in 2000 to assess long-term (21 years) effects of the mechanical treatments on plant and soil carbon (C) and nitrogen (N) dynamics. Live plant biomass, standing dead, litter, and root biomass and soil (to 60 cm depth) were assessed to provide estimates of quantity and distribution of vegetation, soil and total ecosystem C and N. Soil profile N mass was significantly higher for both mechanical treatments compared to the nontreated control. Both the single and double ripped plots also showed significantly higher quantities of total ecosystem N than their respective controls. Neither mechanical treatment, however, had a significant effect on soil or total ecosystem organic C mass or distribution. The “tillage effect” of the mechanical renovation treatments may account for the lack of organic C response because of enhanced decomposition and oxidation of soil organic C during initial treatment implementation.