Nutrient losses in eroded sediment after fire in eucalyptus and pine forests in the wet Mediterranean environment of northern Portugal

Nutrients sorbed onto eroded sediment from small bounded plots installed in newly burned and unburned Eucalyptus globulus and Pinus pinaster forests i n the Agueda Basin, north-central Portugal were measured over an 18-month p eriod. The data are used to determine: (i) the effects of fire on nutrient loss, (ii) the importance of fin-induced losses on soil fertility, and (iii ) temporal variations in nutrient losses. Fire increased losses of total ni trogen, exchangeable potassium and available phosphorus by 3-4 orders of ma gnitude. This is attributed to increased erosion and high nutrient concentr ations at the soil surface in the burned forests, where burning of organic matter and vegetation increased nutrient availability. Enhanced rates of lo ss were sustained for at least 3 years, resulting in much greater post-fire nutrient losses than reported in drier regions of the Mediterranean. Losse s of available P had the greatest potential for reductions in soil fertilit y. (C) 1999 Elsevier Science B.V. All rights reserved.