Relief influence on the spatial distribution of the Atlantic Forest cover on the Ibiúna Plateau, SP

Several studies suggest that, on a large scale, relief conditions influence the Atlantic Forest cover. The aim of this work was to explore these relationships on a local scale, in Caucaia do Alto, on the Ibiúna Plateau. Within an area of about 78 km², the distribution of forest cover, divided into two successional stages, was associated with relief attribute data (slope, slope orientation and altitude). The mapping of the vegetation was based on the interpretation of stereoscopic pairs of aerial photographs, from April 2000, on a scale of 1:10,000, while the relief attributes were obtained by geoprocessing from digitalized topographic maps on a scale of 1:10,000. Statistical analyses, based on qui-square tests, revealed that there was a more extensive forest cover, irrespective of the successional stage, in steeper areas (>10 degrees) located at higher altitudes (>923 m), but no influence of the slope orientation. There was no sign of direct influence of relief on the forest cover through environmental gradients that might have contributed to the forest regeneration. Likewise, there was no evidence that these results could have been influenced by the distance from roads or urban areas or with respect to permanent preservation areas. Relief seems to influence the forest cover indirectly, since agricultural land use is preferably made in flatter and lower areas. These results suggest a general distribution pattern of the forest remnants, independent of the scale of study, on which relief indirectly has a strong influence, since it determines human occupation.

Vários estudos sugerem que as condições do relevo influenciam, em larga escala, a cobertura da Mata Atlântica. Este trabalho teve por objetivo explorar estas relações em escala local, na região do Planalto de Ibiúna, denominada de Caucaia do Alto. Numa área de cerca de 78 km², procurou-se associar a cobertura florestal, dividida em dois estádios sucessionais, com atributos do relevo (declividade, orientação de vertente e altitude). O mapeamento da vegetação foi feito a partir da interpretação de pares estereoscópicos de fotografias aéreas de abril de 2000, na escala 1:10.000, enquanto os atributos do relevo foram gerados por geoprocessamento a partir de cartas topográficas digitalizadas, em escala 1:10.000. As análises estatísticas, baseadas em testes de qui-quadrado, revelam que há maior cobertura florestal, independentemente do estádio sucessional, em áreas mais íngremes (>10 graus) e situadas em altitudes mais elevadas (>923 m), porém não há influência da orientação de vertente. Não há indícios de influência direta do relevo sobre a cobertura florestal, através de gradientes ambientais que poderiam agir na regeneração florestal. Também não foram obtidas evidências de que estes resultados possam ser influenciados pelo distanciamento a estradas ou centros urbanos, ou ainda pelo respeito às áreas de preservação permanente. O relevo parece determinar o recobrimento florestal, principalmente por condicionar o uso agrícola dos solos, que se dá preferencialmente em áreas mais planas e baixas. Estes resultados sugerem um padrão geral de influência do relevo sobre a distribuição dos remanescentes florestais, independentemente da escala de estudo, onde o relevo atua indiretamente ao condicionar a ocupação humana.

Idiopathic ventricular tachycardia--characterisation and radiofrequency ablation.

Forty patients (14 women and 26 men; mean age 40 +/- 13 years, range 7 to 60) diagnosed to have idiopathic ventricular tachycardia (right ventricular 28, left ventricular 12) underwent electrophysiologic study and radiofrequency catheter ablation. Echocardiography, signal averaging, magnetic resonance imaging and cardiac catheterisation with angiography were used as indicated to rule out identifiable underlying etiologies. Gross localisation of the area of origin of the ventricular tachycardia from the surface electrocardiogram could be made in all cases. Accurate localisation of the site of origin was done by activation mapping and pace mapping. Radiofrequency application was successful in achieving a cure in 34 (85%) patients, with a mean of 8.3 +/- 4.7 energy applications and a fluoroscopy time of 38 +/- 19 minutes. Unsuccessful cases were characterised by wide and slurred QRS complexes during ventricular tachycardia, possibly indicating a deeper intramyocardial or epicardial site of origin of the tachycardia. Radiofrequency ablation appears to be the treatment of choice for symptomatic idiopathic ventricular tachycardia, having a high success and safety rate.