DIFFERENTIATION OF ARBOREAL VEGETATION IN THREE SECTORS OF A FOREST FRAGMENT RELATED TO ITS HISTORICAL DISTURBANCES

Abstract

A fragmenta\ue7\ue3o florestal \ue9 um dos principais agentes de redu\ue7\ue3o da biodiversidade, interferindo diretamente nos processos ecol\uf3gicos da comunidade arb\uf3rea. Este trabalho teve como objetivo avaliar par\ue2metros de diversidade, estrutura e composi\ue7\ue3o em tr\ueas setores de um remanescente florestal com hist\uf3ricos distintos de perturba\ue7\uf5es. A vegeta\ue7\ue3o arb\uf3rea foi avaliada em 24 parcelas de 10 7 10 m, amostrando um total de 1228 indiv\uedduos vivos. Foram quantificados o \uedndice de diversidade de Shannon, a equabilidade de Pielou e os estimadores jackknife de primeira e segunda ordem. Os indiv\uedduos amostrados foram distribu\ueddos em classes de di\ue2metro e o valor de import\ue2ncia (VI) foi calculado para as esp\ue9cies. Foi tamb\ue9m realizada uma An\ue1lise de Correspond\ueancia Retificada (DCA) para verificar se h\ue1 distin\ue7\ue3o entre os tr\ueas setores. Constatou-se que o setor onde ocorreu corte raso e queima da vegeta\ue7\ue3o possui maior abund\ue2ncia e riqueza, por\ue9m, tem a pior equabilidade, o que condiz com os efeitos das perturba\ue7\uf5es, corroborado tamb\ue9m pela distribui\ue7\ue3o nas classes diam\ue9tricas e pelas esp\ue9cies de maior VI. O setor que n\ue3o possui perturba\ue7\uf5es e que est\ue1 situado em um local com maior variedade de ambientes apresentou diversidade, estrutura e composi\ue7\ue3o condizentes com estas situa\ue7\uf5es. J\ue1 o outro setor, que n\ue3o sofreu corte raso, est\ue1 submetido ao pisoteio pelo gado e \ue9 ambientalmente semelhante ao primeiro setor, apresenta par\ue2metros condizentes com a aus\ueancia de perturba\ue7\uf5es severas. Por outro lado, a menor diversidade ambiental tamb\ue9m o diferencia, o que o coloca em uma situa\ue7\ue3o intermedi\ue1ria.Forest fragmentation is one of the main causes of biodiversity loss, directly affecting the ecological processes. This study aimed to evaluate tree diversity, structure, and composition parameters in three sectors of a forest fragment with distinct disturbance records. The arboreal vegetation was evaluated in twenty-four 10 7 10 m plots, sampling a total of 1,228 living individuals. We calculated Shanon\u2019s diversity index, Pielou\u2019s equability, and jackknife estimators of first and second orders. The sampled individuals were distributed in diameter classes and the importance value (VI) was calculated for each species. It was made a Detrended Correspondence Analysis (DCA) to verify whether there were significant distinctions between the sectors. It was noticed that the sector where there was clear cutting and vegetation burning in a recent past had higher abundance and richness but also the worst equability. That corresponds to the effects of perturbation as confirmed by the tree diameters and the presence of species of greater importance value. The sector that had no record of disturbance, situated in a location with greater variety of microenvironments, presented diversity, structure, and composition consistent with a no disturbance scenario. The other sector, which did not have clear cutting, was subjected to cattle trampling presented ecological parameters consistent with the absence of major disturbances. On the other hand, this third sector had the smallest environmental diversity, which puts this last sector in an intermediate situation