Nitrogenase Activity Associated with Decayed Wood of Living Northern Idaho Conifers

ABSTRACT

Nitrogen fixation, as determined by the acetylene reduction technique, was demonstrated in decay columns of western larch and western white pine caused by Phellinus pini, western red cedar caused by Postia sericeomollis, and western hemlock and grand fir caused by Echinodontium tinctorium. Nitrogenase activity varied with tree species, fungal pathogen, wood decay stage, and seasonal moisture-temperature regimes within decaying stems. Nitrogen fixation potential in the productive forest ecosystems of northern Idaho was calculated between 0.06 kg/ha/yr and 4.91 kg/ha/yr and was primarily dependent on volume of decay in live standing trees on site.

Key Words:

• acetylene reduction
• asymbiotic nitrogen fixation
• site productivity
• nitrogen input