Revista Recursos Hdricos
Volume 33, Nmero 1, Maio 2012

DOI: 10.5894/rh33n1-4
O texto deste artigo foi submetido para reviso e possvel publicao em Maro de 2012, tendo sido aceite pela Comisso de Editores Cientficos Associados em Abril de 2012. Este artigo parte integrante da Revista Recursos Hdricos, Vol. 33, N 1, 47-59, Maio de 2012.

Perdas de nutrientes por escorrncia superficial em trs encostas florestais recentemente ardidas

Nutrient losses by overland flow at three recently burnt forested hillslopes

Ana Machado¹, Isabel Nunes², Mrio Cerqueira³, Renata Pinto⁴, Martinho Martins⁵, Diana Patoilo⁶, Jacob Keizer⁷

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1 - Mestre em Engenharia do Ambiente /// Bolseira de Investigao do Centro de Estudos do Ambiente e do MAR (CESAM) e do Departamento de Ambiente e Ordenamento da Universidade de Aveiro /// Mestre em Engenharia Civil
2 - PhD, Professora Auxiliar Convidada do Departamento de Ambiente e Ordenamento da Universidade de Aveiro e colaboradora do Centro de Estudos do Ambiente e do MAR (CESAM)
3 - PhD, Professor Auxiliar do Departamento de Ambiente e Ordenamento da Universidade de Aveiro e membro do Centro de Estudos do Ambiente e do MAR (CESAM)
4 - Mestre em Engenharia do Ambiente /// Bolseira de Investigao do Centro de Estudos do Ambiente e do MAR (CESAM) e do Departamento de Ambiente e Ordenamento da Universidade de Aveiro
5 - Mestre em Engenharia do Ambiente /// Bolseiro de Investigao do Centro de Estudos do Ambiente e do MAR (CESAM) e do Departamento de Ambiente e Ordenamento da Universidade de Aveiro
6 - PhD, Tcnica Superior do Departamento de Ambiente e Ordenamento da Universidade de Aveiro
7 - PhD, Investigador Auxiliar do Centro de Estudos do Ambiente e do MAR (CESAM)

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RESUMO: Numa rea ardida do concelho de Sever do Vouga, foi estudada as perdas de quatro nutrientes (clcio, magnsio, potssio, sdio) por escorrncia superficial escala de microparcela. Foram selecionadas trs encostas queimadas, com dois tipos de floresta (plantaes de eucalipto e pinheiro bravo) e dois tipos de geologia (granito e xisto). Foram analisadas amostras de escorrncia referentes aos primeiros 6 meses aps incndio e, ainda, amostras de cinza e solo (camada de 0-2cm de profundidade). As concentraes de nutrientes foram determinadas por espectroscopia atmica.
As amostras de cinza apresentaram maiores concentraes de clcio, enquanto as do solo apresentaram maiores concentraes de potssio. Porm, nem as amostras de cinza nem as amostras do solo revelaram diferenas relevantes entre as trs encostas queimadas. O potssio tambm foi o elemento que registrou maiores perdas por escorrncia em todas as encostas. Quanto s diferenas entre as encostas, o pinhal teve menores perdas que os dois eucaliptais, e o eucaliptal em xisto menores perdas que o eucaliptal em granito. Estas diferenas estavam sobretudo relacionadas com diferenas nas quantidades de escorrncia superficial e no com diferenas nas concentraes dos nutrientes.

Palavras-chave: escorrncia, eroso, incndios florestais, nutrientes.

ABSTRACT: In a recently burnt area in the municipality of Sever do Vouga, north-central Portugal, the losses off four soil nutrients (potassium, calcium, sodium, magnesium) by overland flow were studied at the micro-plot scale. Three hillslope slopes were selected with two types of tree plantations (Eucalyptus Globulus and Maritime Pine) and two types of parent material (granite and schist). This study analyzed the overland flow samples collected during the first six months after the wildfire as well as samples of the ash layer and upper soil layer (0-2cm depth) collected immediately after the fire. The laboratory analysis of the samples involved digestion with acids and determination of nutrient concentrations by atomic spectroscopy.
Calcium attained the highest concentrations in the ash samples as opposed to potassium in the soil samples. Nutrient concentrations in neither ash nor soil samples differed markedly between the three hillslopes. Potassium was also the nutrient that revealed the highest losses by overland flow at all three sites. Nutrient losses were markedly lower for the pine than eucalypt slopes and for the eucalypt slope on schist than on granite. These differences were primarily due to differences in runoff amounts.

Keywords: erosion, nutrients, overland flow, forest wildfire.

 

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