Nutrient export from watersheds on Mt. Desert Island, Maine, as a function of land use and fire history.

ABSTRACT

A study of 13 small (less than 7.5 km(2)) watersheds on Mt. Desert Island, Maine, was conducted from January 1999 to September 2000 to determine nutrient export delivery to coastal waters around the island, and to determine whether a series of wildfires in 1947 have affected nutrient export in burned watersheds. Nutrient export (nitrate-nitrogen, total nitrogen, total phosphorus) was determined for each watershed during the study period, and was normalized by watershed area. The yield of nitrate-nitrogen (N) ranged from 10 to 140 kg/km(2)/year. Total N yield ranged from 42 to 250 kg/km(2)/year. Total phosphorus (P) yield ranged from 1.4 to 7.9 kg/km(2)/year. Watersheds entirely within Acadia National Park (lacking human land-based nutrient sources) exported significantly less total N and total P than watersheds that were partly or entirely outside the park boundary. Nitrate-N export was not significantly different in these two groups of watersheds, perhaps because atmospheric deposition is a dominant source of nitrate in the study area. No relation was observed between burn history and nutrient export. Any effect of burn history may be masked by other landscape-level factors related to nutrient export.