Nitrification Potentials of an Old‐Field Chronosequence in Campton, New Hampshire

Successional changes in available soil nitrogen may be a key to understanding the dynamics of secondary succession. Nitrification potentials of forest floors from an old—field chronosequence in Campton, New Hampshire, were measured in the laboratory for 9 mo. Total nitrate production per unit organic matter decreased with increasing stand age. Although nitrate production decreased in older forest floors of the chronosequence, total nitrogen removals during the incubation were relatively similar. Nitrate production was strongly correlated with initial forest floor pH (°2 = 0.96, P < .001), but was not correlated with any of five different measures of litter and forest floor tannin content. It appears that decreases in nitrification potential during this secondary succession could have resulted from changing forest floor pH and its effects on microorganisms.