Aporte de material orgânico e nutrientes pela serapilheira e resíduos de colheita e sua relação com variáveis ambientais em plantio de Pinus taeda L. em Quedas do Iguaçu- PR

Abstract

Pinus species have been planted in Brazil for over a century. Many of them were brought by European immigrants, for ornamental purposes and for timber production. The species produce large amount of litter, this is considered an important component of a forest ecosystem, comprising precipitated material to the soil by the biota, which mainly includes leaves, branches, fruits, flowers, roots and animal waste. This material contains high proportion of nutrients and, as decompose, the nutrients it contains are released, giving the cycling of nutrients. Therefore, the objective of this work was to determine the potential contribution of nutrients in a Pinus taeda stand with 22 years old in different management conditions, compared to native forest attestant, by the amount of accumulated litter and crop residues and nutrients contained in this material, in the region of Quedas do Iguaçu-PR. The floristic and phytosociological study was conducted in areas with and without passage of harvester/forwarder and native forest, to the knowledge of the understory vegetation of the stand. In each area were installed three plots of 5 x 10 m and within those sub-plots with 5 x 5 meters for the assessment of regeneration (individuals with CAP < 5 cm) were installed. To better support the characterization of native forest vegetation, we used a study on private reserve of Natural patrimony (RPPN), published by Kleinpaul (2003), located about 5 km from the study area. To study the light incidence in the understory of the plots, were used digital luximeter, measured the light intensity in ten random points inside the plot. To determine the accumulated litter and the harvest biomass residues, 4 plots were demarcated in each treatment. With the use of a metal square frame with 50 cm of side, were collected, at random, in each plot, four samples of this material on the ground. These samples were analyzed for levels of organic carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). The area with the passage of machines showed the highest number of individuals and species, demonstrating the influence of light on development of understory, beyond to show much accumulated litter in relation to the area without passage of machinery and native forest. In relation to nutrients, these varied the intake and content in the different treatments, according to the following order of decreasing C > N > Mg > Ca > K > P.