 introduction to nitrogen cycling in watersheds nitrogen is the most commonly limiting nutrient in forests and nitrogen cycling is altered by acid rain and other sources of nitrogen pollution changes in nitrogen cycles are also one of the key ways in which climate change alters forest growth health and composition working with drs ivan j fernandez jean macrae kevin simon sarah nelson stephen norton and tsutomo ohno links to all researchers pages as an outgrowth of the 25year study of the bear brook watershed  teachers and students in the northeast are helping to develop a regionwide system for understanding seasonal changes in nitrogen availability in forested watersheds  nitrogen cycling and watersheds   nitrogen cycling in watersheds  