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A perda de carbono através dos sedimentos produzidos por erosão hídrica, para além de representar um prejuízo económico constitui também um factor de degradação ambiental. O solo constitui o maior reservatório de carbono na biosfera terrestre e pequenas variações negativas aí registadas podem conduzir a mudanças substanciais na concentração atmosférica de CO2, com implicações sobre o clima global. O presente estudo tem por objectivo avaliar a perda de carbono por erosão hídrica em povoamentos florestais instalados sob 4 técnicas com diferente intensidade de preparação do solo (tratamentos). O ensaio foi instalado em Lamas de Podence, concelho de Macedo de Cavaleiros, a 700 m de altitude, com precipitação média anual de 655 mm e temperatura média anual de 12ºC. O delineamento experimental incluiu 6 micro-parcelas de erosão (repetições) por tratamento, onde se procedeu à recolha de sedimento e escoamento superficial. Os resultados apresentados referem-se aos primeiros 13 eventos, num total de cerca de 1200 mm de precipitação num ano, durante os quais se acompanharam as perdas de água e sedimento em micro-parcelas de 2,3 a 2,9 m2. A perda de sedimento no solo sem intervenção mecânica (TSMO) foi de 22,9 g m-2 num ano. Nas áreas sujeitas a preparação do terreno e plantadas, os valores da perda de sedimento foram 7 a 11 vezes superiores. Como esperado, a perda de solo foi superior no tratamento de maior intensidade de mobilização do solo (RCVC), equivalente a 2,5 t ha-1 num ano. A perda de carbono apresenta uma relação muito estreita com a perda de sedimento (r2 = 0,989). O efeito das técnicas de preparação do terreno nas perdas de sedimento e carbono não é muito expressivo, no entanto, estes parâmetros tendem a aumentar com a intensidade da mobilização. Efeitos locais, ao nível da micro-parcela, como o declive, o coberto superficial e a rugosidade superficial, contribuem para explicar os resultados obtidos.
The organic carbon loss through the sediments produced by erosion, in addition to representing an economic loss is also a factor in environmental degradation. The soil is the major reservoir of carbon in the terrestrial biosphere and small negative changes may lead to substantial changes in atmospheric CO2 concentration, with implications on global climate. This study aims to evaluate the carbon loss by erosion in forest stands installed under four techniques with different intensity of site preparation (treatments). The experimental area is located near Bragança, NE Portugal, at 700 m height, mean annual rainfall 655 mm, mean annual temperature 12oC and Mediterranean climate conditions. Soil and water lost were collected after each period of precipitation (named event) from small plots with 2.3 a 2.9 m2, six replicates per treatment. Results now reported are related to the first 13 events, summing about 1200 mm precipitation in one year. Soil loss in the original soil was 22.9 g m-2 in one year. In all areas treated and planted, values of soil loss were 7 to 11 times higher. As expected, soil loss was sharply higher on treatment with high intensity site preparation (RCVC), equivalent to 2.5 t ha-1 in one year. Carbon loss has a very close relationship with sediment loss (r2= 0.989). Differences in soil loss and carbon as affected by site-preparation techniques are not substantial;; nevertheless, they show a tendency to increase with tillage intensity. Local effects at small erosion plot level, such as slope and surface roughness, help explaining results found.
The organic carbon loss through the sediments produced by erosion, in addition to representing an economic loss is also a factor in environmental degradation. The soil is the major reservoir of carbon in the terrestrial biosphere and small negative changes may lead to substantial changes in atmospheric CO2 concentration, with implications on global climate. This study aims to evaluate the carbon loss by erosion in forest stands installed under four techniques with different intensity of site preparation (treatments). The experimental area is located near Bragança, NE Portugal, at 700 m height, mean annual rainfall 655 mm, mean annual temperature 12oC and Mediterranean climate conditions. Soil and water lost were collected after each period of precipitation (named event) from small plots with 2.3 a 2.9 m2, six replicates per treatment. Results now reported are related to the first 13 events, summing about 1200 mm precipitation in one year. Soil loss in the original soil was 22.9 g m-2 in one year. In all areas treated and planted, values of soil loss were 7 to 11 times higher. As expected, soil loss was sharply higher on treatment with high intensity site preparation (RCVC), equivalent to 2.5 t ha-1 in one year. Carbon loss has a very close relationship with sediment loss (r2= 0.989). Differences in soil loss and carbon as affected by site-preparation techniques are not substantial;; nevertheless, they show a tendency to increase with tillage intensity. Local effects at small erosion plot level, such as slope and surface roughness, help explaining results found.
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Fonseca, Felícia; Figueiredo, Tomás; Martins, Afonso (2010). Perda de carbono orgânico por erosão hídrica em povoamentos florestais recém instalados. In Figueiredo, Tomás de; Ribeiro, Luís Frölen; Ribeiro, A.C. (Eds) II Workshop sobre Clima e Recursos Naturais nos Países de Língua Portuguesa: Livro de Resumos. Bragança: IPB. p. 85-86. ISBN 978-972-745-113-5