Nitrogen Cycling and Dynamics in Upland Managed and Preserved Watersheds of the Adirondack Mountains, New York

Abstract

This study investigated nitrogen cycling differences between management systems in the Adirondacks. The definition of managed site was that there had been active logging within the past twenty-five years and the sites fit into the preserve category because they had no active logging within the past eighty-five years. The soil nitrogen cycle is complex and can be disturbed in many ways, including timber harvesting management practices. These disturbances were investigated over the summer of 2005 when logged and preserve forested watershed soil nitrogen was examined. Five soil cores were taken from each of two managed and two preserved watersheds over a two-day period. These four adjacent watersheds have identical temperature, precipitation, and climate so this eliminates outside influence. Chemical and physical parameters including organic matter content, nitrate, ammonium and total Kjeldahl nitrogen (TKN) were compared between watershed management practices. No significant differences were found between organic matter, nitrates, or ammonium, but there was a significant difference in TKN. Managed sites contained higher concentrations of TKN. These differences are most likely not due to direct influences by the timber harvesting that has taken place in the last twenty-five years. The explanation possibly lies in the composition of the forest since the site with less deciduous trees had a higher nitrogen concentration in the soil. This could be due to a lower carbon to nitrogen (C:N) ratio in the forest litter resulting in litter that is broken down more easily.