Use of Acetylene Reduction for Estimating Nitrogen Fixation in Woody Debris
1988
Hendrickson, O. Q.
Both endogenous C₂H₄ formation and C₂H₄ arising from reduction of C₂H₂ must be accurately measured in N₂ fixation studies using C₂H₂ reduction. Previous work with forest soil has shown that C₂H₄ formed in air is not an appropriate control for endogenous C₂H₄ formation. This study compared different controls for endogenous C₂H₄ formation during C₂H₂ reduction studies of woody logging debris. Amounts of C₂H₄ formed by decaying wood in the presence of C₂H₂ plus either of two noncompetitive inhibitors of C₂H₂ reduction (CO, (NH₄)₂SO₄) were greater (p <0.01) than amounts of C₂H₄ formed in air. Ambient air controls therefore underestimated endogenous C₂H₄ formation, and would overestimate N₂ fixation rates. Controls using (NH₄)₂SO₄ were not suitable for routine use due to alteration of sample moisture content. With CO as an inhibitor, endogenous C₂H₄ formation averaged 23% of total C₂H₄ formed in the presence of C₂H₂ across a range of moisture contents. Field data on C₂H₄ produced by logging slash in the presence of C₂H₂ alone are discussed in light of these findings. In the future, C₂H₂ reduction studies of N₂ fixation in decaying wood should employ CO controls for endogenous C₂H₄ formation.
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