Rhizosphere nitrogen fixation (C-b2-sH-b2-s reduction) associated with the major species of the tall grass prairie.

Abstract

Three aspects of rhizophere nitrogen fixation(C2H2 reducation) in the tall grass prairie were investigated in this study. First, a survey was done to determine how many plant species have nitrogen fixing ability associated with their roots. Over 40 species from the POACEAE, FABACEAE and ASTERACEAE were tested. More than 30 of those species gave a positive response. Second, the effect of moisture stress on rhizosphere nitrogen fixation was studied. Xylem Pressure Potential (XPP) and rhizosphere nitrogen fixation were measured through the summer for Andropogon gerardi, ~. scoparius, Sorghastru~ nutans, and Panicum virgatum. As XPP decreased, the rate of nitrogen fixation also decreased. This may be a response to decreased photosynthesis or an increased deactivition of nitrogenase from exposure to oxygen. Third, the response of rhizosphere nitrogen fixation to spring burning was measured. Adjacent burned and unburned sites were chosen for this study. The rate of nitrogen fixation in the burned prairie was consistently higher than in the unburned prairie for all four of the major tall grass species.