Efeito de borda sobre os microrganismos do solo em fragmento florestal do Parque Nacional do Iguaçu

Abstract

When it comes to sustainability, biodiversity conservation is seen as one of society's greatest challenges at the turn of the century. As a consequence of the high index of anthropogenic actions in the environment, some ecosystems had their structure partially or completely altered. One of the main effects caused by these actions is the fragmentation of ecosystems and, as a result, the formation of edges, being responsible for causing changes in the physical, chemical and biological means, making this area bordering different from the rest of the fragment. Among the main species affected by the formation of borders are edaphic microorganisms, because they have great sensitivity to physical and chemical changes in the environment. As forest fragmentation and consequently edge effect directly affect edaphic microorganisms, the study of soil microbial composition of the fragment is considered to be effective for edge effect analysis. Samples were collected in two areas of the Iguaçu National Park, one with advanced ecological succession and another with intermediate ecological succession (former Estrada do Colono), and soil chemical analyzes were performed for organic matter index, pH, phosphorus and nitrogen, and analyzes of the microbial populations present for actinobacteria, cellulolytic bacteria, phosphate solubilizing bacteria and fungi. Actinobacteria populations showed great sensitivity to edge effect in both study areas, ranging from 66% in the first area, from the initial point to the final point, within the fragment, and the second area showed a 58% developmental variation. Fungi populations showed greater influence of anthropic activities and varied in 58% in the first area of study, from the point with greater anthropic activity to the one with less activity, and 63% in the second area. The organic matter showed a low difference between the points, except for the point of greatest anthropic activity in the second area of study, which varied in 28% of the other points. The phosphorus indices presented great differences only in the points located in the area of intermediate ecological succession, due to the process of soil regeneration, reaching variation of 35%. The pH values were presented without great variations and both areas studied. The number of undergrowth plants showed great differences between the points of greatest anthropic activity in both areas, with a variation of 46% in the first area and 87% in the second area.