Stage Description
Stage 0 The nitrogen cycle is dominated by forest and microbial uptake. Nitrate concentrations are very low throughout the year. No nitrate leaches during the growing season, and low concentrations of nitrate run off during snowmelt.
Stage 1 The nitrogen cycle is still dominated by forest and microbial uptake. Although little nitrate leaches during the growing season, nitrate concentrations increase during snowmelt.
Stage 2 The nitrogen cycle is dominated by nitrate leakage and denitrification instead of forest and microbial uptake. The uptake of nitrogen by forest plants and microbes decreases rapidly, and nitrate leaches into stream water. Nitrate concentrations are also higher during the growing season, and concentration changes are small throughout the year.
Stage 3 The nitrogen retention capacity of the forest decreases considerably, and nitrate leakage exceeds nitrogen deposition. Nitrate concentrations are higher than those of precipitation throughout the year, and there is no change in seasonal nitrate concentrations.