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Title: LONG-TERM EFFECTS OF MECHANICAL RENOVATION OF A MIXED-GRASS PRAIRIE: II. CARBON AND NITROGEN BALANCE

Author
item MIYAMOTA, D - USDA-NRCS
item OLSON, R - UNIVERSITY OF WYOMING
item Schuman, Gerald

Submitted to: Arid Land Research and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2003
Publication Date: 5/1/2004
Citation: Miyamota, D.L., Olson, R.A., Schuman, G.E. 2004. Long-term effects of mechanical renovation of a mixed-grass prairie: ii. carbon and nitrogen balance. Arid Land Research and Management. 18:141-151.

Interpretive Summary: Mechanical renovation of Great Plains rangelands has been shown to be effective in increasing forage production. In 1979, a study was initiated on a northern mixed-grass prairie of southeastern Wyoming to determine the effects of rangeland ripping (single and double) on forage production. These treatments were found to increase forage production over the 4-year (1979-1982) study period. Forage production was still greater on the treated rangelands 20 years later (1999-2000). The purpose of this research was to evaluate the effect of these mechanical renovation treatments on the carbon and nitrogen balance of the soil-plant system. The long-term increased forage production increased soil and ecosystem nitrogen over the untreated plots. However, neither mechanical renovation treatment had a significant affect on the soil or ecosystem organic carbon mass. The loss of carbon from the system as a result of the "tillage effect" in 1979 appears to have been significant through the enhanced decomposition and oxidation of soil organic matter during that disturbance. Therefore, even though forage production was increased over the long-term it only restored the soil organic carbon back to the level prior to implementation of the renovation practice, limiting this rangeland management practice as a tool to enhance carbon sequestration over this time period.

Technical Abstract: In 1979, a study was initiated on the northern mixed-grass prairie of southeastern Wyoming 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 non-treated 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.