**3.1.5 Measurement of asymbiotic nitrogen fixation rates in woody debris and forest floor**

Measures of nitrogenase activity were used as an index of nitrogen fixation, based on an adaptation of the acetylene reduction assay (Hardy et al., 1973). Sampling was carried out on five occasions (August 22 and September 25, 1994, and May 15, June 18 and July 20, 1995) at the three study sites. From an analysis of historical weather data and preliminary sample tests, we believe that no nitrogen fixation activities occur from November to April due to low temperature. The more details on measurements and calculations were described by Wei et al. (1998).
