Resumen

TEMPORETTI, Pedro F. Long term effect of forest fires in the water quality of two Andean-Patagonian streams, Argentina. Ecol. austral [online]. 2006, vol.16, n.2, pp.157-166. ISSN 1667-782X.

Fires which affect both the native and the forest forage species are one of the most important environmental impacts in the Patagonian region. The analyses of the effects produced by this type of disturbance should be focused on: 1) changes occurred in the basin, and 2) changes occurred in the water quality of the water bodies involved. There are not previous reports about the relevance of the effects of forest fires on the water quality of natural environments in the Nahuel-Huapi National Park. The aim of this work is to fill this gap through the study of the impact of fire in two mountain streams. The variables sampled showed that the water quality of the streams changed as a consequence of forest fires. It was possible to detect the effects in the water until three years after the fire. The pH, conductivity and suspended solid values, were in the same order as that of rivers and streams of the region. The total phosphorus, nitrite and ammonia concentration in water were low for the six sites of Chall-Huaco and Ñireco rivers at all times. However, the nitrate concentration was higher in the fire forest affected sites, with the 37% of the total nitrogen measured. The nitrate load coming from the Chall-Huaco river to the Nahuel Huapi lake was of 2.6 Tn/year, 5.8 Tn/year and 53.5 Tn/year in low, middle and high flow respectively. The concentration of nitrate in water appears to be the most effective way to evaluate the impact that forest fires can have in this basin.

Palabras clave : Nutrients; Fire; Waterstreams.

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