PRESENCE AND BEHAVIOR OF COLLOIDAL NITROGEN AND PHOSPHORUS IN A SIERRA-NEVADA WATERSHED SOIL

Soil colloids can play a significant role in the profile migration of organic and inorganic nutrient species, We investigated the presence o f colloidal N and P in a Lake Tahoe basin ecosystem following 6 yr of drought, Artificial rainfall was used to determine the release and mob ility of colloidal N and P in soils of the Incline Creek, Nevada, wate rshed, Colloidal, rather than inorganic nutrient species, were the dom inant forms present in soil water extracts, Concentrations of colloida l N increased following rainfall simulation, whereas concentrations of colloidal P decreased, and both appeared to be influenced by the pres ence and dissolution of hydrophobic organic coatings, Colloidal N and P must be considered a potential source of mobile nutrients in soils o f the Sierra Nevada.