Use of Acetylene Reduction for Estimating Nitrogen Fixation in Woody Debris
- O. Q. Hendrickson
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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