Microbial transformations of labelled nitrogen in a clear-cut pine plantation.

Labelled nitrogen was used to evaluate the effects of intensive forest management on soil nitrogen transformations. The total release of N into inorganic forms (ammonium plus nitrate) was much greater than net N mineralization in all treatments. Immobilization of N by microbes was greatest in minimally-treated harvested plots, while the turnover of N within soil microbes was greatest in intensively-treated plots. Ammonium was immobilized 2.4-3.2 times more rapidly than nitrate in havested plots; nitrification in disturbed sites could thus increase the availability of N to regrowing vegetation.