Banco de sementes do solo de uma floresta de terra firme na fazenda Rio Capim, Paragominas, PA, aos 13 meses após exploração de impacto reduzido

Abstract

There is a few studies on soil seed bank in the Amazonian forests, a very few in logged forest. A series of 180 soil samples were collected from an area where a reduced impact logging was applied in the Rio Capim Forest Management Unit, which belongs to Cikel Brazil Verde Madeiras Ltda., municipality of Paragominas, PA. Three treatments were randomly distributed in 36 50mx50m plots: T0 – unlogged area; T1 – logged area, where only the commercial boles were collected; and T2 - logged area, where the commercial boles plus the coarse woody debois were collected. Each one of the 36 plots were divided in 25 10mx10m subplots, from which 5 were chosen to be collected the soil samples in plots of 25cm x 25cm x 5cm. The samples were put in a green house and monitored during a six-month period to evaluate the germination from the soil seed bank. The seedlings were counting and identified monthly. The foristic composition of the soil seed bank in the three forest conditions (treatments) together is constituted of 113 species from 94 genera and 51 families. In the logged forest where only the commercial boles were collected (T1) there are 74 species, In the logged forest where the boles plus the coarse woody debois were collected (T2) there are 67 species and in the unlogged forest (T0) there are 72 species. The variation between treatments is very small, indicating that the intensity of logging applied in the area has not influenced significantly in the floristic composition of the seed bank. The total number of seedlings was 4.323, being higher in the unlloged forest, followed by the logged area where only the commercial boles were collected (T1) and the logged area where both the commercial boles and the coarse woody debois were collected (T2). There was no significant difference among the three forest conditions, although the logged area collecting boles plus coarse woody debois (T2) had presented a smaller number of seedlings. That same tendency was observed on the species frequency, therefore showing that the logging has not influenced significantly the abundance or the species distribution on area. Among the ecologically most important species in the area, 57% belong to tree life form and, because of that, they can be used in the timber industries, but studies are needed involving natural regeneration of these species, as well as their young and adult populations. Also there is a need to study the technological characteristics of the species to inform about their timber and non-timber uses, mainly for those species most important on abundance and distribution on area, including shrubs, herbs and lianas. The tree species Cecropia obtusa and Heisteria densifrons are the most abundant and mort frequent species in the study area. Bixa arborea and Glycidendron amazonicum which also are among the most abundant and the most frequent species have already their wood properties studied and some use were identified, so atentiou must be payed to those especies during the planning of management and use of the forest resources in the study area.