Phosphorus and Nitrogen Dynamics in Streams Associated with Wildfire: A Study of Immediate and Longterm Effects

Stream nutrient data were collected for five years from a series of paired watersheds within and outside of a wildfire area. After the month-long fire, phosphorus and nitrogen levels increased from 5 to 60 fold over the background levels. Total phosphorus and total nitrogen during this period increased significantly. After a few weeks, nutrient concentrations declined to background levels. Dissolved nutrient concentrations in impacted streams remained up to five times higher than in unimpacted streams for the following five years. High gradient watersheds showed a higher immediate concentration of soluble phosphorus, while the concentrations in moderate gradient watersheds were higher during the 3-5 years after the fire. Nitrogen compounds were higher immediately following the fire, probably as a function of different mobilization mechanisms.